LX470 AHC issues - pressure sensor 1998 Vs. 2002 (2 Viewers)

[suprasvobodea]

There is a solenoid (SLCA in Techstream) that opens and closes the valve between the Accumulator and the pump. If you apply 12V in the expected direction (+ is the bottom pin, negative i the top on the motor plug) it will very quickly (<1sec) reach high pressure with a loud knock. I do not recommend keeping power in that way. I have toyed with the idea to manually open the solenoid and then apply power to the motor, but not yet

I have had some success with applying reverse polarity to the motor plug (negative bottom, positive top pin) for 5-7 seconds, which usually allows the system to pressurise for a while. In my case the issue is air in the fluid and accumulator with a broken off bleeder. Sometimes I have to run it in reverse 4-5 times to be able to lift it to N and rise pressure in the Acc.

<<UPDATE 2>> 5/15/24


Let me update you on my latest troubleshooting methodology.

1. I removed the connector for the pump and the accumulator so I could apply 12V to both. I directly wired 12V to the pump continuously from the battery and the STRANGE THING IS>...it started humming (working) with just the + side 12V applied... NO neg lead attached to the other pin!!! I thought you had to have a complete closed circuit of voltage to make a motor or light work ??!! Why does the pump work with just a 12 + applied to the positive terminal??
2. Next>> THE ACCUMULATOR SOLENOID:I then applied 12V+ to the pos side ( L-Y) wire and ground to ( L-R) neg.- wire with an auto-test probe to the solenoid of the accumulator. This opened the solenoid so the pump could FILL the accumulator. When I opened up the bleeder on the accumulator a WHOLE bunch of air /bubbles flowed out. Seeing this, I thought WOW!!!! I think I solved the 1762 issue with air in the system. SO .. to date, I have done the following:
   1. Opened the HP fitting on both front shocks, raised the front of the truck on jack stands, attached a hose to the top, and added oil till it was full. Put the top fitting on, open the bleeder valve at the front shocks, compress the LCA, close the bleeder, then release the compressed LCA. Did that TWICE. I also did the rear axle. I don't know if I need to REMOVE the shocks again( I replaced all the bushings) and compress them completely or not. I don't see how that makes any difference if I did the full range ON the vehicle.
3. So, with some confidence again, I prepare for the active test, by jumping Tc-T1 and pressing DOWN 5 + times within 5 seconds on the UP-DOWN rocker switch, thinking it's going to work... NO...!!! I STILL GET THE FAIL-SAFE MODE AND 1762 CODE!
4. I am still waiting for the NEW PS on the pump, but again...., everyone says that they have never seen a PS go bad and I have replaced it TWICE now. This next one will be the 3rd!

 

[suprarx7nut]

<<UPDATE 2>> 5/15/24


Let me update you on my latest troubleshooting methodology.

1. I removed the connector for the pump and the accumulator so I could apply 12V to both. I directly wired 12V to the pump continuously from the battery and the STRANGE THING IS>...it started humming (working) with just the + side 12V applied... NO neg lead attached to the other pin!!! I thought you had to have a complete closed circuit of voltage to make a motor or light work ??!! Why does the pump work with just a 12 + applied to the positive terminal??
2. Next>> THE ACCUMULATOR SOLENOID:I then applied 12V+ to the pos side ( L-Y) wire and ground to ( L-R) neg.- wire with an auto-test probe to the solenoid of the accumulator. This opened the solenoid so the pump could FILL the accumulator. When I opened up the bleeder on the accumulator a WHOLE bunch of air /bubbles flowed out. Seeing this, I thought WOW!!!! I think I solved the 1762 issue with air in the system. SO .. to date, I have done the following:
   1. Opened the HP fitting on both front shocks, raised the front of the truck on jack stands, attached a hose to the top, and added oil till it was full. Put the top fitting on, open the bleeder valve at the front shocks, compress the LCA, close the bleeder, then release the compressed LCA. Did that TWICE. I also did the rear axle. I don't know if I need to REMOVE the shocks again( I replaced all the bushings) and compress them completely or not. I don't see how that makes any difference if I did the full range ON the vehicle.
3. So, with some confidence again, I prepare for the active test, by jumping Tc-T1 and pressing DOWN 5 + times within 5 seconds on the UP-DOWN rocker switch, thinking it's going to work... NO...!!! I STILL GET THE FAIL-SAFE MODE AND 1762 CODE!
4. I am still waiting for the NEW PS on the pump, but again...., everyone says that they have never seen a PS go bad and I have replaced it TWICE now. This next one will be the 3rd!

You're so close to the solution it would bite you if it were a snake.

Point number 2. You bled a little air. Nice work. Now do that sequence again. And again. And again. Again. Again. Again. Again. Again. Again.

Of course the active test won't run. It never does. You've still got to much air and the system knows that.

Force the pump to run. Force the accumulator if you need to. Bleed. Repeat. Over and over and over. Eventually the pump will run as it's supposed to.

 

[suprasvobodea]

Good writeup, as always @IndroCruise.

One thing that been making it difficult to help him. Is his painting with a broad bush, then remembering giving detail after I've draw conclusion and written a response based on statements made. One very important point is, when did failsafe C1762 first accrue. Which I may have wrong. But I have after, shock reinstalled possible after pump R&R. If earlier, say pre globes or after accumulator. This would change where I'd first look.

______________________________________________
"
Vehicle Background and Symptoms:

Vehicle: 2002 – LX470,
Correspondent: @suprasvobodea
Location: Dallas, Texas, USA,
Fall 2023: Four new OEM ‘globes’ installed ex Impex,
Fall 2023: New OEM Height Control Accumulator installed ex Impex,
Jan 2024: Front ‘Shock Absorbers’ removed to replace bushes, then re-installed,
Jan 2024: Rear ‘Shock Absorbers’ removed to replace bushes, then re-installed,
>>>?? Failsafe C1762
Mar 2024: New OEM AHC Pump sub-assembly installed ex Impex
>>>?? Failsafe C1762
"
___________________________________________

Wasn't it after shock install, when first C1762 kick in failsafe. At first, no mention of pre flushing and bleeding of shocks. He then came back and said he did. With, little detail as to how.

Let assume a mistake made, where shock still had some air internal/deep in them. Then in raising LCA with shock attached, so to attach shocks top nut. Shock compressed a bit, and then top nut attached. He in then topped off shock and attached HP fitting. Then removing jack allowing LCA to fully extend shock after HP fitting attached. Any extension of shock, would have drawn in some air from HP line. HP lines to globes, were likely empty of most fluid at this point. He then lowers vehicle, with all bleeders closed. Compressing air, rather than leaving a pathway for escape (open bleeders).

The picture gets foggery, as to how much fluid in reservoir and at what points. Hearing what he thought empty reservoir. Was it empty???. If he had filled to the with 1" top, from a full 2.5L tin, empting tin into reservoir. It can't have emptied, with all good globes, accumulator and shocks pre filled. Unless it was running out of a leak, which he should have seen leak.

Also his 20 second N to H. Very likely due to T-bar out of adjustment, not carrying enough weight.

Conclusion:

Air in AHC shocks and lines, plus carrying to much weight on shocks.

You're so close to the solution it would bite you if it were a snake.

Point number 2. You bled a little air. Nice work. Now do that sequence again. And again. And again. Again. Again. Again. Again. Again. Again.

Of course the active test won't run. It never does. You've still got to much air and the system knows that.

Force the pump to run. Force the accumulator if you need to. Bleed. Repeat. Over and over and over. Eventually the pump will run as it's supposed to.

SupraRx7nut:

Thank you for responding tonight. I'm feeling like a mechanical failure & very down right now.................!!! I've never had my ass kicked so badly with ANY electro-Mechancial issue like this in 40 years!!!!!!!!!
I repeated this 2 more times on the front wheels after my first success with the bubbles /air. I applied 12V to both the accumulator solenoid and pump. HOWEVER,... No more bubbles or air was exiting the accumulator when I opened up the bleeder on the accumulator. I did the front LH globe as well since it was right there by the accumulator. All that came out of the accumulator was clear, bubble-free fluid. I did not check the rear shocks again after the previous removal, do I have to remove the top fitting after lifting the rear on jack stands again and compress each side shock like the front LCA?? Does anyone know HOW MUCH AIR in the shocks /Accumulator /lines causes the fail-safe error code.....?
I guess I have no choice but to raise the rear on jack stands again, open up the rear shocks, attach a hose to the top of each, and pour oil into a funnel till it's full. Then seal the top, open the bleeder, and compress the axle to force out any more air/ fluid again.

So, what you're telling me is I'm really REAAAALY close to getting the active test to run ??? BTW, I did apply 12V directly to the pump, and pierced the 2 wires at the PS to test the voltage with the pump running ( NOT ENGINE) since the pump running is the same and I only got 0.568 V running and 0.505 V with the pump NOT running. This is still not to spec at 1.7V so could it be possible that this PS is NOT functioning correctly? The FSM manual, as I said in previous posts, states it is supposed to be 1.6-1.8V !!??!

Is it possible that the AHC ECU is faulty ...? Should I even be going there ...? I read in another post from 2001LC or someone that it WAS the AHC ECU that was faulty after all. I have no idea how to test this, except trying another one, but I feel this is a <10% chance of being the issue.

 

[suprarx7nut]

SupraRx7nut:

Thank you for responding tonight. I'm feeling like a mechanical failure & very down right now.................!!! I've never had my ass kicked so badly with ANY electro-Mechancial issue like this in 40 years!!!!!!!!!
I repeated this 2 more times on the front wheels after my first success with the bubbles /air. I applied 12V to both the accumulator solenoid and pump. HOWEVER,... No more bubbles or air was exiting the accumulator when I opened up the bleeder on the accumulator. I did the front LH globe as well since it was right there by the accumulator. All that came out of the accumulator was clear, bubble-free fluid. I did not check the rear shocks again after the previous removal, do I have to remove the top fitting after lifting the rear on jack stands again and compress each side shock like the front LCA?? Does anyone know HOW MUCH AIR in the shocks /Accumulator /lines causes the fail-safe error code.....?
I guess I have no choice but to raise the rear on jack stands again, open up the rear shocks, attach a hose to the top of each, and pour oil into a funnel till it's full. Then seal the top, open the bleeder, and compress the axle to force out any more air/ fluid again.

So, what you're telling me is I'm really REAAAALY close to getting the active test to run ??? BTW, I did apply 12V directly to the pump, and pierced the 2 wires at the PS to test the voltage with the pump running ( NOT ENGINE) since the pump running is the same and I only got 0.568 V running and 0.505 V with the pump NOT running. This is still not to spec at 1.7V so could it be possible that this PS is NOT functioning correctly? The FSM manual, as I said in previous posts, states it is supposed to be 1.6-1.8V !!??!

Is it possible that the AHC ECU is faulty ...? Should I even be going there ...? I read in another post from 2001LC or someone that it WAS the AHC ECU that was faulty after all. I have no idea how to test this, except trying another one, but I feel this is a <10% chance of being the issue.

Forget the shocks. Don't break those loose. They're fine. They're designed to purge air. No special treatment needed.

Forget the pressure sensor.

Forget the active test.

Just apply power to the pump, bleed everywhere you can. That's it. You just need to flow those gas bubbles out of the system. Until you do, that pump is not building pressure and that pressure sensor is never going to read correctly. It's not broken, there's just no pressure. That hydro pump can't build gas pressure.

Run the pump, bleed. It's boring and tedious.

You've got this.

 

[suprasvobodea]

Forget the shocks. Don't break those loose. They're fine. They're designed to purge air. No special treatment needed.

Forget the pressure sensor.

Forget the active test.

Just apply power to the pump, bleed everywhere you can. That's it. You just need to flow those gas bubbles out of the system. Until you do, that pump is not building pressure and that pressure sensor is never going to read correctly. It's not broken, there's just no pressure. That hydro pump can't build gas pressure.

Run the pump, bleed. It's boring and tedious.

You've got this.

OK.. But you know that I MUST apply 12V to the accumulator solenoid manually to open it to allow oil to flow, while the pump is working. BTW. I replaced the pump assy with a new one from IMPEX, but it won't run backward when I reverse the pos and neg leads to it??!! It locks up... and won't hum like it does normally. Also, how come the pump works when I just apply 12V pos to the one lead on it???? How is the pump grounded to the frame ...? Shouldn't I need to ground the neg lead on the pump ...? If there is a logical electrical explanation, then fine.,. but this might be something is an issue IDK..!

 

[suprarx7nut]

OK.. But you know that I MUST apply 12V to the accumulator solenoid manually to open it to allow oil to flow, while the pump is working. BTW. I replaced the pump assy with a new one from IMPEX, but it won't run backward when I reverse the pos and neg leads to it??!! It locks up... and won't hum like it does normally. Also, how come the pump works when I just apply 12V pos to the one lead on it???? How is the pump grounded to the frame ...? Shouldn't I need to ground the neg lead on the pump ...? If there is a logical electrical explanation, then fine.,. but this might be something is an issue IDK..!

Applying power to the solenoid: ok sure, sounds good.

I wouldn't worry about running the pump backwards now. That's just a fringe concept to get gas flowing out of the system. If you've got a means of bleeding gas, focus on that.

12v turning on the pump: obviously there's a ground path. Unsure what it is, wouldn't be concerned about it, haha. Get the gas out. That's all you need now.

 

[Moridinbg]

1. I removed the connector for the pump and the accumulator so I could apply 12V to both. I directly wired 12V to the pump continuously from the battery and the STRANGE THING IS>...it started humming (working) with just the + side 12V applied... NO neg lead attached to the other pin!!! I thought you had to have a complete closed circuit of voltage to make a motor or light work ??!! Why does the pump work with just a 12 + applied to the positive terminal??

Oh yeah, it does that . My diesel is dual battery from the factory, so whenever I do that I just disconnect the nearby battery and use that. I guess the chassis of the pump motor is grounded, so it spins with just the +. When you connect it to a separate battery it works as expected.

 

[suprasvobodea]

Oh yeah, it does that . My diesel is dual battery from the factory, so whenever I do that I just disconnect the nearby battery and use that. I guess the chassis of the pump motor is grounded, so it spins with just the +. When you connect it to a separate battery it works as expected.

Ok. Obviously the pump motor is grounded to the frame … just wasn’t aware of it ! I’ll continue to apply 12V to pump and accumulator solenoid to pump oil into the system. Seems like a terrible way to make the system work… but it’s the only way I can get it to work , still waiting for new PS from IMPEX- Japan

 

[IndroCruise]

Ok. Obviously the pump motor is grounded to the frame … just wasn’t aware of it ! I’ll continue to apply 12V to pump and accumulator solenoid to pump oil into the system. Seems like a terrible way to make the system work… but it’s the only way I can get it to work , still waiting for new PS from IMPEX- Japan

• Ensure vehicle is on the ground with wheels bearing the weight of the vehicle, not on stands with wheels hanging,

• Forget about C1762 for the moment -- you have seen air in the system – and air in the system is the mostly likely cause of C1762 as advised to you by @suprarx7nut, @2001LC and @IndroCruise -- sure, there are other possibilities for C1762 but put them aside for now, you have seen air, focus on air removal FIRST,

• Definitely put aside your worries about the Pressure Sensor for now -- yes, I know that it is not giving the test voltages you expect -- but there may be various reasons for those results, including Pump unable to deliver required pressure due to air in the system -- just leave it for now,

• Put aside your worries about “Active Test” -- this will not work when C1762 is present (nor with various other faults) -- there is no point in getting cross about this, it is what it is, and it is a fact-of-life -- move on for now,

• To repeat, focus on getting air out first,

• Look at the attached schematic and visualise all the places where air or bubbly fluid may be parked – long pipes, ‘globes’, ‘shock absorbers’, various pipe junctions/joiners etc, etc -- you have seen air, you KNOW it is in there somewhere and possibly in multiple places,

• BEFORE PROCEEDING FURTHER CLEAR ALL DTC’S,

• Check for strong pump delivery using 12 volt direct connection to a battery and cracking open the delivery pipe joiner at the AHC Pump (or my preference would be at the pipe joiner at the Height Control Accumulator – NOT the bleeder here – the bleeder connects through to the internal body of the Height Control Accumulator, does not connect to the pipeline),

• Open and then close all 5 bleeders one-by-one, furthest from Pump first, then others progressively to release whatever fluid and air (bubbles) may come out, using pressure from the weight of the vehicle,

• Opening the bleeder at Height Control Accumulator will release any pressure and fluid inside – and the nitrogen pressure will drive the piston all the way forward – and then the Height Control Accumulator is EMPTY,

• Then forget about the Height Control Accumulator for now -- DON’T fuss with its solenoid valve -- this solenoid valve ONLY admits fluid to the Height Control Accumulator -- it is NOT some kind of gateway to the rest of the system,

• The initial objective is get fluid through the rest of the system -- and out through the bleeder valves near the ‘globes’,

• The next step is to try and get fluid past the “normally closed” Levelling Valves in the Control Valve Assembly and onwards and out through the bleeder valves at the ‘globes’,

• First, try direct operation by 12 volt direct connection from battery to the AHC Pump AND WITH THE FURTHEST BLEEDER OPEN, AND, IF THIS WORKS, REPEAT PROGRESSIVELY WITH BLEEDERS AT OTHER ‘GLOBES’. NOTE: IN THIS STEP, THE IDEA IS JUST TO FLUSH THE LINES, NOT TRYING TO RAISE THE VEHICLE JUST YET,

• IF THE ABOVE STEP DOES NOT WORK, REPEAT WITH 12 VOLT BATTERY DIRECT CONNECTION TO THE AHC PUMP, BUT ALSO ATTEMPT TO START THE AHC SYSTEM BY PRESSING THE “UP” BUTTON ON THE CENTRAL CONSOLE TO SEE IF THIS WILL CAUSE THE LEVELLING VALVES TO OPEN,

• IF THE ABOVE STEP DOES NOT WORK, DISCONNECT THE 12 VOLT BATTERY DIRECT CONNECTION,

• THEN RECONNECT AHC PUMP MOTOR, START ENGINE, CLEAR ALL DTC’S, KEEP FURTHEST BLEEDER OPEN, OPERATE AHC “UP” BUTTON – YES, C1762 WILL KEEP RECURRING -- BUT CLEAR DTC's THEN REPEAT, CLEAR DTC's THEN REPEAT, CLEAR DTC's THEN REPEAT -- IN AN ATTEMPT TO ACHIEVE SOME FLUID MOVEMENT,

• REPORT BACK WITH DESCRIPTION OF RESULTS -- THEN THERE CAN BE A DISCUSSION ABOUT NEXT STEPS -- HOW TO RAISE THE VEHICLE -- OR LOOK FOR ALTERNATIVE CAUSES AND SOLUTIONS,

 

[suprasvobodea]

View attachment 3633988

View attachment 3633990
View attachment 3633995

• Ensure vehicle is on the ground with wheels bearing the weight of the vehicle, not on stands with wheels hanging,

• Forget about C1762 for the moment -- you have seen air in the system – and air in the system is the mostly likely cause of C1762 as advised to you by @suprarx7nut, @2001LC and @IndroCruise -- sure, there are other possibilities for C1762 but put them aside for now, you have seen air, focus on air removal FIRST,

• Definitely put aside your worries about the Pressure Sensor for now -- yes, I know that it is not giving the test voltages you expect -- but there may be various reasons for those results, including Pump unable to deliver required pressure due to air in the system -- just leave it for now,

• Put aside your worries about “Active Test” -- this will not work when C1762 is present (nor with various other faults) -- there is no point in getting cross about this, it is what it is, and it is a fact-of-life -- move on for now,

• To repeat, focus on getting air out first,

• Look at the attached schematic and visualise all the places where air or bubbly fluid may be parked – long pipes, ‘globes’, ‘shock absorbers’, various pipe junctions/joiners etc, etc -- you have seen air, you KNOW it is in there somewhere and possibly in multiple places,

• BEFORE PROCEEDING FURTHER CLEAR ALL DTC’S, DONE

• Check for strong pump delivery using 12 volt direct connection to a battery and cracking open the delivery pipe joiner at the AHC Pump (or my preference would be at the pipe joiner at the Height Control Accumulator – NOT the bleeder here – the bleeder connects through to the internal body of the Height Control Accumulator, does not connect to the pipeline), I couldn't get at the flare nut for the input line to the accumulor since it is on top of the accumulotr and I would have had to remove the front LH globe again ( didn't have the 30mm cluth fan wrench) so I just removed the fitting from the attenuator ( first device after the outlet) The flow is appears to be fine, but i could not exactly tell . Remember , this is a BRAND NEW pump assy. so i assume it should be good !

• Open and then close all 5 bleeders one-by-one, furthest from Pump first, then others progressively to release whatever fluid and air (bubbles) may come out, using pressure from the weight of the vehicle, I opend each bleeder, there was no pressure in system to force anything but a dribble of fluid out. THe only air came out from the LH front GLOBE , which is the closest to the accumltor and would have the most oil after i manually opend the solenoid and forced the pump to work with 12V direct.y.

• Opening the bleeder at Height Control Accumulator will release any pressure and fluid inside – and the nitrogen pressure will drive the piston all the way forward – and then the Height Control Accumulator is EMPTY, DONE

• Then forget about the Height Control Accumulator for now -- DON’T fuss with its solenoid valve -- this solenoid valve ONLY admits fluid to the Height Control Accumulator -- it is NOT some kind of gateway to the rest of the system,

• The initial objective is get fluid through the rest of the system -- and out through the bleeder valves near the ‘globes’,

• The next step is to try and get fluid past the “normally closed” Levelling Valves in the Control Valve Assembly and onwards and out through the bleeder valves at the ‘globes’, I believe that these solenoids must be energized too ( just like the accumulaotr) for them to opem and allow oil to them. Doing this had NO EFFECT when i pressed UP buttom

• First, try direct operation by 12 volt direct connection from battery to the AHC Pump AND WITH THE FURTHEST BLEEDER OPEN, AND, IF THIS WORKS, REPEAT PROGRESSIVELY WITH BLEEDERS AT OTHER ‘GLOBES’. NOTE: IN THIS STEP, THE IDEA IS JUST TO FLUSH THE LINES, NOT TRYING TO RAISE THE VEHICLE JUST YET, Nothing came out when i did this.

• IF THE ABOVE STEP DOES NOT WORK, REPEAT WITH 12 VOLT BATTERY DIRECT CONNECTION TO THE AHC PUMP, BUT ALSO ATTEMPT TO START THE AHC SYSTEM BY PRESSING THE “UP” BUTTON ON THE CENTRAL CONSOLE TO SEE IF THIS WILL CAUSE THE LEVELLING VALVES TO OPEN, Nothing happend, pushing the UP switch had no effect

• IF THE ABOVE STEP DOES NOT WORK, DISCONNECT THE 12 VOLT BATTERY DIRECT CONNECTION,

• THEN RECONNECT AHC PUMP MOTOR, START ENGINE, CLEAR ALL DTC’S, KEEP FURTHEST BLEEDER OPEN, OPERATE AHC “UP” BUTTON – YES, C1762 WILL KEEP RECURRING -- BUT CLEAR DTC's THEN REPEAT, CLEAR DTC's THEN REPEAT, CLEAR DTC's THEN REPEAT -- IN AN ATTEMPT TO ACHIEVE SOME FLUID MOVEMENT, I did this 7 times, and yes within 2-3 seconds the flashing OFF light came back , and it was the 1762 code, just as you said it would.

• REPORT BACK WITH DESCRIPTION OF RESULTS -- THEN THERE CAN BE A DISCUSSION ABOUT NEXT STEPS -- HOW TO RAISE THE VEHICLE -- OR LOOK FOR ALTERNATIVE CAUSES AND SOLUTIONS, I also applied 12 V to the pump AND the accumulator solenoid again after doing the first step of bleeding all globes and accumultor. This seems to be the ONLY WAYT TO GET OIL to the accumultor to even have a chance at bleeding the whole system.

Indocruise

Thank you for your reply.... I have been anticipating it for a couple of days!

BTW>>> I don't know if you remember, but there is a NEW OEM pump sub-assy in the system, so there is no chance of plugged screens, and there SHOULD be a strong fluid flow at the flare nut at the accumulator. installed the 3 new O-rings in the new pump when I received it 2 or 3 months ago.

<<<UPDATE >>> 5/18/24
I will try all the steps now and report back later tonight in a few hours... SEE MY RESULTS IN BLUE FOR EACH QUESTION ABOVE!



WHAT ARE THE NEXT STEPS.... I only removed some bubbles and air from the LH globe. Do I need to check some wiring ..??? This just does not make any sense to me. HOW DO I FORCE THE SYSTEM TO PUMP OIL TO BLEED AIR FROM IT, WHEN I CAN'T EVEN GET IT TO RUN TO DO THAT?

 

[IndroCruise]

Indocruise

Thank you for your reply.... I have been anticipating it for a couple of days!

The connection at the accumulator is of course a flare nut and requires a 14mm flare wrench. This nut (which was rounded off when I tried to remove it) was the reason I had to buy a NEW SS line from the accumulator back to the pump ( it runs across the frame in the middle of the truck and then bends 90 to the front along the RH side rail) I will disconnect the fitting at accumulator since you indicated you "preferred" this. I will attach a hose to the end, place it in a container, and apply 12 V to the pump. BTW>>> I don't know if you remember, but there is a NEW OEM pump sub-assy in the system, so there is no chance of plugged screens, and there SHOULD be a strong fluid flow at the flare nut at the accumulator, but I will check to confirm. I installed the 3 new O-rings in the new pump when I received it 2 or 3 months ago.

I will try all the steps now and report back later tonight in a few hours

Good!! I think that it is unlikely that there is a problem inside the new AHC Pump – BUT we don’t KNOW that, so a positive report of flow and pressure for all to see is important. It also is much easier than dismantling and inspecting the AHC Pump.

The only time you can claim that “there is no chance of plugged screens” is when that is proven one way or another. Stating that you have a new Pump is neither good diagnosis nor proof of Pump performance nor proof of anything else. It is an assumption about the condition of the Pump.

In this situation with the Pump on open circuit (no resistance to flow), the delivered flow should be strong. This a positive displacement gear pump. The flow is directly proportional to the speed of rotation of the gears UNLESS there is a blockage OR UNLESS somehow the fluid is bypassing INSIDE the Pump. This can happen in an old Pump due to wear of the gears or the casing -- or worn internal o-rings above the gearcases as mentioned by @BullElk -- these are different to the o-rings or seals outside of the AHC Pump sub-assembly which you replaced when you installed the new Pump sub-assembly.

Or if the internals of the Pump have been wrongly assembled – such as with the “notch” in the gear cases on wrong side of Pump which will result in no escape path for fluid exiting the meshing gears and cause weak action of the Pump if it works at all, OR, if the Pump sub-assembly has been over-tightened when installed, making it difficult for the gears to turn and may result in the drive linkage from the motor being damaged.

You DO have a new OEM Pump.
Please confirm that the sub-assembly has not been opened at the time of installation nor at any other time.
Is this correct?
If YES, suggest accept after doing the simple tests above that the Pump has been assembled correctly at the factory – and then don’t worry about any of the above erudite items just now.
If NO, please tell us exactly what you have done.

Meanwhile, stay focussed on getting air out of the system.

Just know that it should be impossible to stop the flow from an operating AHC Pump with your thumb (use a rubber glove). If you can stop the flow easily, then new or old, there is a problem inside the AHC Pump sub-assembly. As an idea of pressure, remember that in a healthy system the Pump is capable of building pressure at the Height Control Accumulator to about 10.5 MPa against strong resistance. You won’t be able to 'dead-head' the AHC Pump (completely block the delivery) at this sort of pressure with your thumb!! Also know that a positive displacement gear pump only creates pressure when there is resistance to flow, so it is important to feel the pressure, not just watch the open circuit flow.

Let’s hope that with this simple test you can confirm positively (not assume) that all is good with the AHC Pump delivery and pressure.

Also, if you disconnect at the Height Control Accumulator and run the AHC Pump, it means that you have run fluid through the pipe to that point. This means that fluid has gone past the Attenuator which occasionally is reported as gas or air accumulation point.

Let’s also hope that you also can confirm positively (not assume) by this simple test that all is good in the pipeline as far as the Height Control Accumulator. (You could check this at the input pipe at the Control Valve Assembly -- but this is less accessible, which is why I have suggested the Height Control Accumulator, which is just on the opposite of the LHS chassis rail, so near enough).

Then continue with the steps outlined in my previous post, focussing on the effort to get the air-polluted fluid moving.

Just a few more words of explanatory detail for your background information:

• @2001LC has addressed an important point in an earlier post but it is worth expanding the explanation: When you decided to refill again the ‘shock absorbers’ and compress them while in place on the vehicle and using jacks under the LCA’s for the compression, then it means that when done the jacks were removed and the LCA’s dropped -- and the ‘shock absorbers’ decompressed (extended) -- and the wheels were left hanging in the maximum droop position. What happens inside the AHC hydraulic circuit then?? Well, look back at the simple hydraulic circuit diagram in the previous post and visualise the situation. It means that volume inside the ‘shock absorber’ INCREASES (it is a simple strut, there is nothing else in there, see diagram below, it is not really a shock absorber) and so the pressure inside the ‘shock absorber’ DECREASES. (Boyles' Law for gases -- pressure is inversely proportional to volume). The 'shock absorber' acts like a syringe. When the jack is removed and the LCA drops, the ‘shock absorber’ tries to draw fluid back from the hydraulic circuit including from the ‘globes’, also with a push from the nitrogen behind the membranes in the 'globes' – and pulling fluid from as far back as the Levelling Valves where the circuit is closed. There is air in the fluid in the circuit and in the fluid side of the ‘globes’ -- you have seen it -- and it is unsurprising given the amount of disruption the system has had. So the result is that the air-polluted fluid is drawn back into the ‘shock absorbers AGAIN. This why @suprarx7nut says not to bother with such attempts. He is right. It is futile. He knows from experience. It is also the reason that the vehicle now needs to be on the ground for further work, and not left on the jackstands. Please confirm that the vehicle now has its wheels on the ground and they are carrying the weight of the vehicle.
• When you have gone as far as you can, please report back. At this time, please also provide the following basic information as a quick list:
• Year model and location of the vehicle
• Weight of the vehicle
• Front and Rear hub-to-fender tape measurements at each wheel,
• Rake of the vehicle,
• Height Control Sensor readings from Techstream,
• Condition of Height Control Sensors,
• Corresponding physical hub-to-fender ‘ride heights’ measured by tape-measure, and,
• Any indications of inconsistency of hub-to-fender tape measurements with conditions and readings of Height Control Sensors,
• complete Techstream screenshot -- the whole page, not part of the page -- maybe it will be possible to figure out why, on your previous screenshot, "Front Wheel Step" and "Rear Wheel Step" were showing zero and not 8 (at the Damping Force Control Actuators) as expected for a stationary vehicle.

Why is this information requested? Please remember that the vehicle is not visible and cannot be inspected by those trying to help you. The information may turn out to be completely irrelevant but it is among the basic information which should be provided as a simple list when inspection is impossible, not hoping that your readers can find or remember from information from your previous posts. It helps create a clearer and more detailed mental picture of your vehicle. It is not intended to cause a distraction. The current problem should not be as difficult as it has become, so your IH8MUD readers, or you, may be missing something or misunderstanding something.

Meanwhile, the starting point is a resolute effort to get air-polluted fluid moving, so please continue with the steps outlined in my previous post.

Looking forward to your next update!!

 

[suprasvobodea]

Good!! I think that it is unlikely that there is a problem inside the new AHC Pump – BUT we don’t KNOW that, so a positive report of flow and pressure for all to see is important. It also is much easier than dismantling and inspecting the AHC Pump.

The only time you can claim that “there is no chance of plugged screens” is when that is proven one way or another. Stating that you have a new Pump is neither good diagnosis nor proof of Pump performance nor proof of anything else. It is an assumption about the condition of the Pump.

In this situation with the Pump on open circuit (no resistance to flow), the delivered flow should be strong. This a positive displacement gear pump. The flow is directly proportional to the speed of rotation of the gears UNLESS there is a blockage OR UNLESS somehow the fluid is bypassing INSIDE the Pump. This can happen in an old Pump due to wear of the gears or the casing -- or worn internal o-rings above the gearcases as mentioned by @BullElk -- these are different to the o-rings or seals outside of the AHC Pump sub-assembly which you replaced when you installed the new Pump sub-assembly.

Or if the internals of the Pump have been wrongly assembled – such as with the “notch” in the gear cases on wrong side of Pump which will result in no escape path for fluid exiting the meshing gears and cause weak action of the Pump if it works at all, OR, if the Pump sub-assembly has been over-tightened when installed, making it difficult for the gears to turn and may result in the drive linkage from the motor being damaged.

You DO have a new OEM Pump.
Please confirm that the sub-assembly has not been opened at the time of installation nor at any other time.
Is this correct? I did remove the 2 cap screws - just to look at the gears , but i DID NOT REMOVE THEM . i was just curious as to the tolerance of them compared to my old pump. I knew that there was a notch in it and i did NOT NEED TO TAKE ANY CHANCES messing it up!!!!
If YES, suggest accept after doing the simple tests above that the Pump has been assembled correctly at the factory – and then don’t worry about any of the above erudite items just now.
If NO, please tell us exactly what you have done.

Meanwhile, stay focussed on getting air out of the system.

Just know that it should be impossible to stop the flow from an operating AHC Pump with your thumb (use a rubber glove). If you can stop the flow easily, then new or old, there is a problem inside the AHC Pump sub-assembly. As an idea of pressure, remember that in a healthy system the Pump is capable of building pressure at the Height Control Accumulator to about 10.5 MPa against strong resistance. You won’t be able to 'dead-head' the AHC Pump (completely block the delivery) at this sort of pressure with your thumb!! Also know that a positive displacement gear pump only creates pressure when there is resistance to flow, so it is important to feel the pressure, not just watch the open circuit flow. I did not check the flow yet when it was disconnected at the Attenuator., its rather difficult /messy with oil dripping from the removed line due to gravity of the tank, but I AGREE WITH YOU! I WILL APPLY 12V TO THE PUMP AND TRY TO dead-head the flwo with a rubber glove on. I know i should NOT BE ABLE TO RESTRAIN IT! ( just like a garden hose with 50psi of pressure ... it will just force out around your thumb. I will do this when i get back home. >> UPDATE 5/21>>>> " HOUSTON ... WE HAVE A PROBLEM!! " - When i removed the flare nut from outlet of pump assy , and had 12V applied running, i was able to STOP THE FLOW OF OIL WITH MY THUMB!! There is NO WAY to prevent even a garden house with 30 psi pressure to prevent water from exiting with your thumb!!!!! WHen i removed my thumb, there was a weak stream of oil . SO .... THERE MUST BE SOMETHING GOING ON WITH THE NEW PUMP I INSTALLED FROM IMPEX! The question is , WHAT DO I DO NOW? I know i need to remove the pump assy and but what do i look for with a new pump gear set from the factory? How can a brand new pump NOT WORK PROPERLY?? Is this the source of my problem? it sure is suspicious!!

Let’s hope that with this simple test you can confirm positively (not assume) that all is good with the AHC Pump delivery and pressure.

Also, if you disconnect at the Height Control Accumulator and run the AHC Pump, it means that you have run fluid through the pipe to that point. This means that fluid has gone past the Attenuator which occasionally is reported as gas or air accumulation point.

Let’s also hope that you also can confirm positively (not assume) by this simple test that all is good in the pipeline as far as the Height Control Accumulator. (You could check this at the input pipe at the Control Valve Assembly -- but this is less accessible, which is why I have suggested the Height Control Accumulator, which is just on the opposite of the LHS chassis rail, so near enough). Its really really difficult as you konw to remove the flare fitting on top of the accumulator unless the Front Left globve is removed! I dont want to do that , if i get a strong flow at the Attenuator ( Can i remove the inlet to it ? Its very difficlut and i have to rasie up the front end since its on the stops right now to get access to the fitting at the bottom of the attenuator that the new SS line that i installed from the Accumultor (due to a rounded flare nut AT THE ATTENUATOR!)

Then continue with the steps outlined in my previous post, focussing on the effort to get the air-polluted fluid moving.

Just a few more words of explanatory detail for your background information:

• @2001LC has addressed an important point in an earlier post but it is worth expanding the explanation: When you decided to refill again the ‘shock absorbers’ and compress them while in place on the vehicle and using jacks under the LCA’s for the compression, then it means that when done the jacks were removed and the LCA’s dropped -- and the ‘shock absorbers’ decompressed (extended) -- and the wheels were left hanging in the maximum droop position. What happens inside the AHC hydraulic circuit then?? Well, look back at the simple hydraulic circuit diagram in the previous post and visualise the situation. It means that volume inside the ‘shock absorber’ INCREASES (it is a simple strut, there is nothing else in there, see diagram below, it is not really a shock absorber) and so the pressure inside the ‘shock absorber’ DECREASES. (Boyles' Law for gases -- pressure is inversely proportional to volume). The 'shock absorber' acts like a syringe. When the jack is removed and the LCA drops, the ‘shock absorber’ tries to draw fluid back from the hydraulic circuit including from the ‘globes’, also with a push from the nitrogen behind the membranes in the 'globes' – and pulling fluid from as far back as the Levelling Valves where the circuit is closed. There is air in the fluid in the circuit and in the fluid side of the ‘globes’ -- you have seen it -- and it is unsurprising given the amount of disruption the system has had. So the result is that the air-polluted fluid is drawn back into the ‘shock absorbers AGAIN. This why @suprarx7nut says not to bother with such attempts. He is right. It is futile. He knows from experience. It is also the reason that the vehicle now needs to be on the ground for further work, and not left on the jackstands. Please confirm that the vehicle now has its wheels on the ground and they are carrying the weight of the vehicle. YES Vehicle is on the stops & on all 4 wheels. Its very low , barely room to even access the bleeders !
• When you have gone as far as you can, please report back. At this time, please also provide the following basic information as a quick list:
• Year model and location of the vehicle 2002 LX 470 Located in DALLAS TX USA.
  • Weight of the vehicle approve 5850 lbs
  • Front and Rear hub-to-fender tape measurements at each wheel, The FL =16.25", FR =16.125" RL = 17.25" RR= 17.25"
  • Rake of the vehicle, NOT SURE WHAT THIS IS? ?? Dont know what this is
  • Height Control Sensor readings from Techstream, (FL=- 3.2 FR=-2.8 Rear = -3.5 >>REMEMBER, THIS IS ON THE BUMP STOPS!)
  • Condition of Height Control Sensors, The LH front had been replaced due to breakage of the arm 5 years ago, The RH is original . THe rear was replaced last year i believe. I removed all 3 of them and checked the impedance per the FSM . when i moved them in the ranges, they were very close to spec per the FSM and all within a few ohms i believe. Basically i didnt see anything that screamed out .... FAILURE... but maybe this is critical .... IDK...?
  • Corresponding physical hub-to-fender ‘ride heights’ measured by tape-measure, and, (do not know , i am out of town till monday )
  • Any indications of inconsistency of hub-to-fender tape measurements with conditions and readings of Height Control Sensors, (THE fact that the measurment from the fender to Center of axel is different by 0.125" corresponds to the lower TECHSTREAM reading... I think this is correct reasoning , Yes??? .
  • complete Techstream screenshot -- the whole page, not part of the page -- maybe it will be possible to figure out why, on your previous screenshot, "Front Wheel Step" and "Rear Wheel Step" were showing zero and not 8 (at the Damping Force Control Actuators) as expected for a stationary vehicle. BTW- when i engaged TECHSTREAM after clearing code and pressing the OFF button so it was NOT visable. and BEFORE i pressed the UP swich that triggers the 1762, i noticed that the Wheel Stops WERE At 8 !!! Again this is somehow related to the fail-safe issue that plagues me at the moment SEE ATTACHMENT PHOTO
• Why is this information requested? Please remember that the vehicle is not visible and cannot be inspected by those trying to help you. The information may turn out to be completely irrelevant but it is among the basic information which should be provided as a simple list when inspection is impossible, not hoping that your readers can find or remember from information from your previous posts. It helps create a clearer and more detailed mental picture of your vehicle. It is not intended to cause a distraction. The current problem should not be as difficult as it has become, so your IH8MUD readers, or you, may be missing something or misunderstanding something.
  
  
  Meanwhile, the starting point is a resolute effort to get air-polluted fluid moving, so please continue with the steps outlined in my previous post.
  
  Looking forward to your next update!! I WILL UPDATE THE DATA THAT I DO NOT KNOW AT THIS TIME ON MONDAY AFTERNOON - (CST )
  
  UPDATE 4 >>> 5/21/24 -ADDITIONAL INFO IN RED ABOVE
  View attachment 3634450

update 3>>5/18/24 @3;30 CST - PLEASE SEE MY RESPONSE IN BLUE

 

[suprasvobodea]

UPDATE 4 >>> 5/21/24 -ADDITIONAL INFO IN RED ABOVE. THE MOST interesting issue was the pump pressure test when I removed the outlet flare nut. When I applied 12V a weak stream of oil exited the side. When I put a rubber-gloved thumb or finger over the outlet, I could STOP THE FLOW of Oil! I cannot even do that with a garden house at 30 psi... !!!! and this is from a NEW, OEM pump assy from IMPEX. What do I do now ....?

 

[IndroCruise]

UPDATE 4 >>> 5/21/24 -ADDITIONAL INFO IN RED ABOVE. THE MOST interesting issue was the pump pressure test when I removed the outlet flare nut. When I applied 12V a weak stream of oil exited the side. When I put a rubber-gloved thumb or finger over the outlet, I could STOP THE FLOW of Oil! I cannot even do that with a garden house at 30 psi... !!!! and this is from a NEW, OEM pump assy from IMPEX. What do I do now ....?

So I have captured a part below of your UPDATE 4 >>> 5/21/24 -ADDITIONAL INFO IN RED ABOVE to make it easier for others such as @2001LC , @suprarx7nut , @BullElk , @Moridinbg or anybodyelse familiar with the internal details of the AHC Pump (or any gear pump) to help with the diagnosis and offer comments on the symptoms described and also critique my interpretation below:

@suprasvobodea >> UPDATE 5/21>>>> " HOUSTON ... WE HAVE A PROBLEM!! " - When i removed the flare nut from outlet of pump assy , and had 12V applied running, i was able to STOP THE FLOW OF OIL WITH MY THUMB!! There is NO WAY to prevent even a garden house with 30 psi pressure to prevent water from exiting with your thumb!!!!! WHen i removed my thumb, there was a weak stream of oil . SO .... THERE MUST BE SOMETHING GOING ON WITH THE NEW PUMP I INSTALLED FROM IMPEX! The question is , WHAT DO I DO NOW? I know i need to remove the pump assy and but what do i look for with a new pump gear set from the factory? How can a brand new pump NOT WORK PROPERLY?? Is this the source of my problem? it sure is suspicious!!

@IndroCruise: If poor AHC Fluid pressure and flow delivery from the recently installed new OEM AHC Pump from IMPEX is as you describe, then the following possibilities come to mind:

1. There is a problem with the motor driving the AHC Pump -- this seems most unlikely and I think that you would sense any motor problems when you were running the Pump directly from a 12 volt battery, OR,
2. The seal at the small drive connector between the Electric Motor and the Pump is damaged or not seated properly and allowing the AHC Pump to suck air, OR,
3. The small drive connector between the Electric Motor and the Pump somehow has become un-seated and is not engaging properly with the Motor or the Pump, causing the Pump not be driven properly, OR,
4. When you took the cover off the new AHC Pump sub-assembly to inspect the gears, the composite back-up rings which sit on top of the o-rings on each of the two gear carriers, or these two o-rings themselves, may have become slightly dislodged. If so, this would cause these two o-rings not to seal properly and this would allow fluid to by-pass internally within the AHC Pump, passing through the by-pass strainer back to the Inlet side of the Pump -- meaning some fluid would be re-circulating, causing low delivery flow and pressure at the Pump discharge, OR,
5. The triangular-looking seal (like an o-ring) on the underside of the cap-plate of the AHC Pump sub-assembly is damaged or not seated properly -- a failure of this seal would have the same affect as item (3) above,
6. The two gears and the gear carriers are not seated properly -- this would have the same affect as item (3) and item (4) above, OR,
7. The set of two gear carriers have been wrongly installed with "notch" on the Discharge side of the Pump. This should be on the Inlet side below the by-pass strainer. If not correct, the Pump cannot deliver correct flow and pressure and may barely work at all, OR,
8. The Inlet Strainer (and possibly but less likely the By-pass Strainer) may be fully or partially blocked with debris from within the system, OR, by sludge which inevitably builds up within the sysyem and may have been disturbed as a result of component change-outs OR may arise from incorrect non-AHC Fluid used at some time in the history of the vehicle, OR, gel which seems to have arisen in defective AHC Fluid in the USA market (associated with the one-litre plastic bottles). Any of these causes would inhibit fluid being drawn from the AHC Tank into the AHC Pump.

All of the above are possible, especially in an AHC Pump which has been disturbed internally.

Of these alternatives, item (8) -- Inlet Strainer partial or complete blockage -- seems more likely than the other alternatives.

Any of the above alternatives would result in C1762 .

The above explanation also may help in understanding why "Active Test" will not operate -- C1762 is designed conservatively to protect the AHC Pump and the AHC system. "Active Test" is not designed as a method of by-passing this protection in the presence of faults and causing damage -- in a similar way that bridging out a failed fuse or open circuit breaker is not a smart thing to do in an electrical circuit -- the cause has to be identified.

The next step is to remove and disassemble the AHC Pump sub-assembly and look for which of above alternatives is the cause of the poor performance of the AHC Pump. This is not difficult and it is easily fixable. If the above notes are are not clear, I am happy to supply some pictures on request which may help, including removal and cleaning of the Strainers. By the way, please do not assume that the Strainers can be cleaned simply by reversing the direction of rotation of the AHC Pump. This does not, and cannot, reverse the direction of fluid flow through the Strainers or through the Pump.

OR, another AHC Pump sub-assembly could be installed if disinclined to dismantle and examine the internals of the existing AHC Pump sub-assembly.

Please note that even when the AHC Pump problem is resolved, there IS air in the AHC system on this vehicle -- you have seen it and reported it -- and C1762 may continue until persistent and repetitive bleeding removes the air. The method of doing this has been described in previous posts in this thread.

Hope this helps!!

 

[suprarx7nut]

A new pump can be immediately clogged with gel from a reservoir that has gel in it.

@suprasvobodea Can you please post pictures? Worth 1000 words, as they say. I would litter the thread with pics. Literally 20 of them. Show us what you're doing and seeing.

I think you may have gel in the screen of your new and old pump. Unless you religiously cleaned out the old reservoir it would be very easy to clog up the new pump and cause what you're describing.

Gel in the old pump (and therefore reservoir) would cause all your symptoms. Installing a new pump without very thorough cleaning of the reservoir would also cause the 1762.

Easy fix if so. Remove pump, clean out reservoir, disassemble pump to reveal inlet screen(s). Carefully clean out screens. Reassemble. Refill with screened fluid.

 

[suprasvobodea]

So I have captured a part below of your UPDATE 4 >>> 5/21/24 -ADDITIONAL INFO IN RED ABOVE to make it easier for others such as @2001LC , @suprarx7nut , @BullElk , @Moridinbg or anybodyelse familiar with the internal details of the AHC Pump (or any gear pump) to help with the diagnosis and offer comments on the symptoms described and also critique my interpretation below:

@suprasvobodea >> UPDATE 5/21>>>> " HOUSTON ... WE HAVE A PROBLEM!! " - When i removed the flare nut from outlet of pump assy , and had 12V applied running, i was able to STOP THE FLOW OF OIL WITH MY THUMB!! There is NO WAY to prevent even a garden house with 30 psi pressure to prevent water from exiting with your thumb!!!!! WHen i removed my thumb, there was a weak stream of oil . SO .... THERE MUST BE SOMETHING GOING ON WITH THE NEW PUMP I INSTALLED FROM IMPEX! The question is , WHAT DO I DO NOW? I know i need to remove the pump assy and but what do i look for with a new pump gear set from the factory? How can a brand new pump NOT WORK PROPERLY?? Is this the source of my problem? it sure is suspicious!!

@IndroCruise: If poor AHC Fluid pressure and flow delivery from the recently installed new OEM AHC Pump from IMPEX is as you describe, then the following possibilities come to mind:

1. There is a problem with the motor driving the AHC Pump -- this seems most unlikely and I think that you would sense any motor problems when you were running the Pump directly from a 12 volt battery, OR,
2. The seal at the small drive connector between the Electric Motor and the Pump is damaged or not seated properly and allowing the AHC Pump to suck air, OR,
3. The small drive connector between the Electric Motor and the Pump somehow has become un-seated and is not engaging properly with the Motor or the Pump, causing the Pump not be driven properly, OR,
4. When you took the cover off the new AHC Pump sub-assembly to inspect the gears, the composite back-up rings which sit on top of the o-rings on each of the two gear carriers, or these two o-rings themselves, may have become slightly dislodged. If so, this would cause these two o-rings not to seal properly and this would allow fluid to by-pass internally within the AHC Pump, passing through the by-pass strainer back to the Inlet side of the Pump -- meaning some fluid would be re-circulating, causing low delivery flow and pressure at the Pump discharge, OR,
5. The triangular-looking seal (like an o-ring) on the underside of the cap-plate of the AHC Pump sub-assembly is damaged or not seated properly -- a failure of this seal would have the same affect as item (3) above,
6. The two gears and the gear carriers are not seated properly -- this would have the same affect as item (3) and item (4) above, OR,
7. The set of two gear carriers have been wrongly installed with "notch" on the Discharge side of the Pump. This should be on the Inlet side below the by-pass strainer. If not correct, the Pump cannot deliver correct flow and pressure and may barely work at all, OR,
8. The Inlet Strainer (and possibly but less likely the By-pass Strainer) may be fully or partially blocked with debris from within the system, OR, by sludge which inevitably builds up within the sysyem and may have been disturbed as a result of component change-outs OR may arise from incorrect non-AHC Fluid used at some time in the history of the vehicle, OR, gel which seems to have arisen in defective AHC Fluid in the USA market (associated with the one-litre plastic bottles). Any of these causes would inhibit fluid being drawn from the AHC Tank into the AHC Pump.

All of the above are possible, especially in an AHC Pump which has been disturbed internally. Of these alternatives, item (8) -- Inlet Strainer partial or complete blockage -- seems more likely than the other alternatives.

Any of the above alternatives would result in C1762 -- and the above explanation also may help in understanding why "Active Test" will not operate -- C1762 is designed conservatively to protect the AHC Pump and the AHC system. "Active Test" is not designed as a method of by-passing this protection in the presence of faults and causing damage -- in a similar way that bridging out a failed fuse or open circuit breaker is not a smart thing to do in an electrical circuit -- the cause has to be identified.

The next step is to remove and disassemble the AHC Pump sub-assembly and look for which of above alternatives is the cause of the poor performance of the AHC Pump. This is not difficult and it is easily fixable. If the above notes are are not clear, I am happy to supply some pictures on request which may help, including removal and cleaning of the Strainers. By the way, please do not assume that the Strainers can be cleaned simply by reversing the direction of rotation of the AHC Pump. This does not, and cannot, reverse the direction of fluid flow through the Strainers or through the Pump.

OR, another AHC Pump sub-assembly could be installed if disinclined to dismantle and examine the internals of the existing AHC Pump sub-assembly.

Please note that even when the AHC Pump problem is resolved, there IS air in the AHC system on this vehicle -- you have seen it and reported it -- and C1762 may continue until persistent and repetitive bleeding removes the air. The method of doing this has been described in previous posts in this thread.

Hope this helps!!

UPDATE 4 >> REPLY
THANK YOU !!! For the reply and the very helpful suggestions. I am going to remove the Pump again, disassemble and inspect it. YES!! PLEASE SEND the pictures and SPECIFIC details on what to look for regarding the gears, notch direction, and anything I need to know about the pump. Also, what seals , what do they look like, and any notes on how to reassemble them CAREFULLY and what to watch for? (Yes, send pictures of exactly what to do with strainers) I truly hope this will solve my 1762 fail-safe issue so I can start bleeding, adjusting Front torsion bars for pressure, and checking the rears to see if I need spacers in the springs to reduce pressure in the rear ( I think I do since I pull a boat occasionally and other trailers)
Yes, I do understand that there is air in system, and will diligently work to resolve this once the system pumps oil and at least fill the accumulator. I hope you are still awake down under, and can reply today. It is 2:00 PM CST here in Dallas TX. Thank you again, i cannot wait to get started and report back to everyone. THIS WILL BE A TREMENDOUS LEARNING EXERCISE FOR EVERYONE WHO EVER EXPERIENCES THIS NIGHTMARE!

 

[suprasvobodea]

A new pump can be immediately clogged with gel from a reservoir that has gel in it.

@suprasvobodea Can you please post pictures? Worth 1000 words, as they say. I would litter the thread with pics. Literally 20 of them. Show us what you're doing and seeing.

I think you may have gel in the screen of your new and old pump. Unless you religiously cleaned out the old reservoir it would be very easy to clog up the new pump and cause what you're describing.

Gel in the old pump (and therefore reservoir) would cause all your symptoms. Installing a new pump without very thorough cleaning of the reservoir would also cause the 1762.

Easy fix if so. Remove pump, clean out reservoir, disassemble pump to reveal inlet screen(s). Carefully clean out screens. Reassemble. Refill with screened fluid.

My reservoir was stained dark brown ( like ALL of them!) and I wanted to try to remove all that staining by soaking it with SIMPLE GREEN concentrate, parts cleaner, royal purple degreaser... even gasoline (It's a great cleaning agent of grease you know!) to get it as clear as possible so i can see the Oil level. So the res was super clean! But I will be disassembling the pump and looking at everything, per INDOCRUISE or your suggestions and pictures if you have any! I will take pictures of my pump once it is removed from the LX and show you what I am seeing as well. I know this helps EVERYONE!

Please, Let me know with any pictures of the pump disassembly process so i don't miss anything or put something back together incorrectly ( like the notch gears!) Thank you for your help and time with this!

 

[suprarx7nut]

My reservoir was stained dark brown ( like ALL of them!) and I wanted to try to remove all that staining by soaking it with SIMPLE GREEN concentrate, parts cleaner, royal purple degreaser... even gasoline (It's a great cleaning agent of grease you know!) to get it as clear as possible so i can see the Oil level. So the res was super clean! But I will be disassembling the pump and looking at everything, per INDOCRUISE or your suggestions and pictures if you have any! I will take pictures of my pump once it is removed from the LX and show you what I am seeing as well. I know this helps EVERYONE!

Please, Let me know with any pictures of the pump disassembly process so i don't miss anything or put something back together incorrectly ( like the notch gears!) Thank you for your help and time with this!

I think @BullElk and @IndroCruise have you covered nicely right here: AHC pump removal with pics - https://forum.ih8mud.com/threads/ahc-pump-removal-with-pics.1227554/

 

[Moridinbg]

I have no idea where this blue and red updates are, it would be best if you just add a complete new post.
Your case sounds oddly similar to my ongoing AHC epic. I had a failed pump, used removed AHC parts, including pump an old cruiser with unknown mileage. That later failed again - dying seagull noises, flashing off, car does not lift. That's when I found out that I can make it run again by driving it in reverse for 5-10 seconds.
Replaced the pump with a brand new pump, including fluid flush (old was dark, but clean), drove fine with it for 10k kilometres, then failed in the exact fricking same way.
Somewhere around this point I tried the same thing - plugged the pump hole with a finger and could stop the flow. Ran the motor in reverse and it was blasting again. I even played around with using the metal pipe that goes down to the attenuator that's bolted to the chassis, to use it as kind of a hose to pump fluid into a bottle and watch the flow when it was squealing.

I also have a broken accumulator bleeder and I keep flushing air out of the sphere bleeders. I am 99% sure that either my accumulator is full of air or as @IndroCruise mentioned - pump is sucking air from around the reservoir/pump/motor, but I doubt that. I have a spare accumulator, but I dread the thought of removing the old one with the ridiculous bolts on top of the chassis.
This came out after maybe 20k km of driving since I put the new pump and fluid. It ain't coke.

Flushed with new fluid, everything settled, could go L <> H for the first time in ages. Could even do it multiple times in a row. I was sure I beat it and finally had working AHC. Drove like that for maybe 200-300km, including 50-100km hard offroad and the seaguls were back Got this out.

Drove like that another 100-150km, all seemed good. Tried L<>H a few times, but unlike last time I had to run the pump in reverse a couple of times, otherwise seagulls. It was still working, but decided to check what is going on with the fluid - bubbles are building up already...

Air is mostly coming from the rear right globe and some from the front right. Left side is mostly good. I am starting to suspect that globe(s) might be leaking.
Unfortunately can't really rely on the graduation test for that, as I am running non-AHC springs in the rear, due to a lot of added weight (RTT, awning, drawer system, aux water and fuel tanks, etc) and rear pressures are out of spec.


I should have removed the damned thing ages ago and installed conventional suspension, but I damn love the AHC ride when it was working and it was working for 280k miles on this car. Nothing else I have tried on friends cruisers comes even close to it and the comfort of adjusting between boaty Comfort and Sport from the cabin...

Don't know if there is something helpful for you in this post, but you are not alone

 

[suprasvobodea]

I have no idea where this blue and red updates are, it would be best if you just add a complete new post.
Your case sounds oddly similar to my ongoing AHC epic. I had a failed pump, used removed AHC parts, including pump an old cruiser with unknown mileage. That later failed again - dying seagull noises, flashing off, car does not lift. That's when I found out that I can make it run again by driving it in reverse for 5-10 seconds.
Replaced the pump with a brand new pump, including fluid flush (old was dark, but clean), drove fine with it for 10k kilometres, then failed in the exact fricking same way.
Somewhere around this point I tried the same thing - plugged the pump hole with a finger and could stop the flow. Ran the motor in reverse and it was blasting again. I even played around with using the metal pipe that goes down to the attenuator that's bolted to the chassis, to use it as kind of a hose to pump fluid into a bottle and watch the flow when it was squealing.

I also have a broken accumulator bleeder and I keep flushing air out of the sphere bleeders. I am 99% sure that either my accumulator is full of air or as @IndroCruise mentioned - pump is sucking air from around the reservoir/pump/motor, but I doubt that. I have a spare accumulator, but I dread the thought of removing the old one with the ridiculous bolts on top of the chassis.
This came out after maybe 20k km of driving since I put the new pump and fluid. It ain't coke.

View attachment 3638040

Flushed with new fluid, everything settled, could go L <> H for the first time in ages. Could even do it multiple times in a row. I was sure I beat it and finally had working AHC. Drove like that for maybe 200-300km, including 50-100km hard offroad and the seaguls were back Got this out.

View attachment 3638041

Drove like that another 100-150km, all seemed good. Tried L<>H a few times, but unlike last time I had to run the pump in reverse a couple of times, otherwise seagulls. It was still working, but decided to check what is going on with the fluid - bubbles are building up already...

View attachment 3638051

Air is mostly coming from the rear right globe and some from the front right. Left side is mostly good. I am starting to suspect that globe(s) might be leaking.
Unfortunately can't really rely on the graduation test for that, as I am running non-AHC springs in the rear, due to a lot of added weight (RTT, awning, drawer system, aux water and fuel tanks, etc) and rear pressures are out of spec.


I should have removed the damned thing ages ago and installed conventional suspension, but I damn love the AHC ride when it was working and it was working for 280k miles on this car. Nothing else I have tried on friends cruisers comes even close to it and the comfort of adjusting between boaty Comfort and Sport from the cabin...

Don't know if there is something helpful for you in this post, but you are not alone

You know, after researching, studying, and reading dozens of posts, from what I can tell, you are contaminating your new fluid with air from INSIDE the closed system. You are correct, the GLOBES are what ruptured with the membrane and you are "airating" under pressure, your AHC Oil ....... just like soda or beer!! The issue is with your Globes. ( Replace them all, sooner than later..) They very reasonable if you get them from IMPEX in Japan ( that where I bought ALL my new parts for the system) . I think I paid $450 for FOUR of them!~! They are ~ $350 a peace if you buy them in the US! I'm happy to say, that your problem is easy to solve!