AHC pump assembly - bench test NG (1 Viewer)

[LX470YYC]

Hello All. Currently trying to diagnose a persistent DTC1762 on my 2003 LX470. Lots of diagnostic history I can share at some point, but right now I'd like to see if anyone has any input specifically on getting flow from the pump assembly.

I've pulled the pump assembly and have bench tested it (Fill reservoir with fluid and apply 12v to motor), with consistent result of zero flow at the output. Motor is good, pump sub assembly seems good as well (gears turn well under bench test, strainers in sub assembly are clean and can be "blown" through). O-rings need a refresh, but their condition along with the nature of the malfunction's progression suggest they're not to blame (happy to have that assumption unlearned though).

My question to limit scope of discussion at this point, is - what are the odds of a blockage within the pump housing between the points marked in the photo, and if possible, how would I go about clearing? It seems that the valve and or the fluid pressure sensor restrict flow on this "high pressure" side of the assembly... can I safely remove the FPS and valve to inspect/clean?

I can't think of many good reasons why a bench test like this would result in NO flow other than a blockage here. What am I missing?

I have a new sub assembly on order from impex, but in the meantime waiting for it, I'd like to make sure I rule out a blockage in what seems like the logical location, and obviously don't want to replace the entire pump/motor due to cost.

TIA.

 

[IndroCruise]

Hello All. Currently trying to diagnose a persistent DTC1762 on my 2003 LX470. Lots of diagnostic history I can share at some point, but right now I'd like to see if anyone has any input specifically on getting flow from the pump assembly.

I've pulled the pump assembly and have bench tested it (Fill reservoir with fluid and apply 12v to motor), with consistent result of zero flow at the output. Motor is good, pump sub assembly seems good as well (gears turn well under bench test, strainers in sub assembly are clean and can be "blown" through). O-rings need a refresh, but their condition along with the nature of the malfunction's progression suggest they're not to blame (happy to have that assumption unlearned though).

My question to limit scope of discussion at this point, is - what are the odds of a blockage within the pump housing between the points marked in the photo, and if possible, how would I go about clearing? It seems that the valve and or the fluid pressure sensor restrict flow on this "high pressure" side of the assembly... can I safely remove the FPS and valve to inspect/clean?

I can't think of many good reasons why a bench test like this would result in NO flow other than a blockage here. What am I missing?

I have a new sub assembly on order from impex, but in the meantime waiting for it, I'd like to make sure I rule out a blockage in what seems like the logical location, and obviously don't want to replace the entire pump/motor due to cost.

TIA.

View attachment 3701280

Yes -- a blockage between the two points circled in RED on your picture is possible. This is very rarely reported -- and It is unclear (at least to me) whether this is because it is a very rare event, or, because the function and possible failure of the Return Valve due to neglected 'hydraulic hygiene', meaning rarely changed sludgy fluid with clogging particulates, is not understood. My personal suspicion is that the occurence is more common than is realised in these vehicles which are now 17 to 25 years old, some of which have been left to operate on ancient, degraded AHC Fluid.

The Return Valve is situated within the housing 48905-60010. Insert this Part Number at https://partsouq.com/ to see some pictures.

Before going further, first it must said (again) that DTC C1762 arises far, far more commonly from

• air in the AHC system which has not been persistently and effectively bled out,
• nitrogen in the AHC system as a result of failing membranes in aged 'globes' (which bleeding will not fix, requires new 'globes'),
• discontunuities or short circuits in connectors and harnesses causing the ECU to respond in strange ways to erroneous electrical inputs.

Anyway, back to your specific question: "What are the odds of a blockage within the pump housing between the points marked in the photo, and if possible, how would I go about clearing?"

Suggest consider a simple, basic hydraulic test after reviewing the hydraulic circuit diagram:

To test:

• Leave the Pressure Sensor in place in the housing 48905-60010 for now,
• Remove the steel AHC discharge pipe at its connection to the housing,
• Operate the AHC Pump with direct 12 volt supply to the motor,
• Observe the flow from the Pump discharge on open circuit (no load and so low pressure but should be very strong flow),
• Attempt to stop the flow with a gloved finger -- it should be impossible to obstruct the flow this way because the finger will not hold back the pressure of which the AHC Pump is capable. The Pump can build sufficient pressure to raise a healthy vehicle against a system pressure of +/- 6Mpa -- that is 60 times atmospheric pressure, and, can raise the pressure in the Height Control Accumulator to 10.5Mpa. True -- there may be a pressure multiplier here due to the relative size of piston diameters and pipeline internal diameters -- but you get the point, a healthy Pump produces pressure which is way beyond the stopping power of a finger.

If all IS good -- meaning strong flow and pressure -- it is reasonable to assume that the AHC pump sub-assembly is healthy. (Remember that the Pump is a Gear Pump, meaning that it is a positive displacement pump and so fluid has to go somewhere, cannot simply churn inside the Pump -- except maybe if the internal O-rings on the gear carriers inside the Pump have been blown completely, short-circuiting the high pressure and low pressure sides of the pump).

If all IS NOT good -- meaning poor flow and pressure -- then is the problem in the Pump, OR, is there a blockage as you suspect??

Repeat the test -- but this time remove the Pressure Sensor. This creates a parallel exit path for fluid from the AHC Pump.

If there is now good flow and pressure through the exit path provided by removal of the Pressure Sensor, then it is reasonable to assume that the Pump is healthy, and that there is a full or partial blockage or mechanical fault at the Return Valve.

See more at the following links with pictures and video clips, including what to do about the Return Valve (if that is what proves to be the problem -- and if it is, then replacing the AHC Pump sub-assembly 48901-60010 will not overcome an issue with the Return Valve which is situated within the housing 48905-60010):

Post #132
LX470 AHC issues - pressure sensor 1998 Vs. 2002 - https://forum.ih8mud.com/threads/lx470-ahc-issues-pressure-sensor-1998-vs-2002.1267066/page-7#post-15549367

Post #139
LX470 AHC issues - pressure sensor 1998 Vs. 2002 - https://forum.ih8mud.com/threads/lx470-ahc-issues-pressure-sensor-1998-vs-2002.1267066/page-7#post-15553902

Post #140
LX470 AHC issues - pressure sensor 1998 Vs. 2002 - https://forum.ih8mud.com/threads/lx470-ahc-issues-pressure-sensor-1998-vs-2002.1267066/page-7#post-15554138

 

[LX470YYC]

Yes -- a blockage between the two points circled in RED on your picture is possible. This is very rarely reported -- and It is unclear (at least to me) whether this is because it is a very rare event, or, because the function and possible failure of the Return Valve due to neglected 'hydraulic hygiene', meaning rarely changed sludgy fluid with clogging particulates, is not understood. My personal suspicion is that the occurence is more common than is realised in these vehicles which are now 17 to 25 years old, some of which have been left to operate on ancient, degraded AHC Fluid.

The Return Valve is situated within the housing 48905-60010. Insert this Part Number at https://partsouq.com/ to see some pictures.

Before going further, first it must said (again) that DTC C1762 arises far, far more commonly from

• air in the AHC system which has not been persistently and effectively bled out,
• nitrogen in the AHC system as a result of failing membranes in aged 'globes' (which bleeding will not fix, requires new 'globes'),
• discontunuities or short circuits in connectors and harnesses causing the ECU to respond in strange ways to erroneous electrical inputs.

Anyway, back to your specific question: "What are the odds of a blockage within the pump housing between the points marked in the photo, and if possible, how would I go about clearing?"

Suggest consider a simple, basic hydraulic test after reviewing the hydraulic circuit diagram:

View attachment 3701341

View attachment 3701342

To test:

• Leave the Pressure Sensor in place in the housing 48905-60010 for now,
• Remove the steel AHC discharge pipe at its connection to the housing,
• Operate the AHC Pump with direct 12 volt supply to the motor,
• Observe the flow from the Pump discharge on open circuit (no load and so low pressure but should be very strong flow),
• Attempt to stop the flow with a gloved finger -- it should be impossible to obstruct the flow this way because the finger will not hold back the pressure of which the AHC Pump is capable. The Pump can build sufficient pressure to raise a healthy vehicle against a system pressure of +/- 6Mpa -- that is 60 times atmospheric pressure, and, can raise the pressure in the Height Control Accumulator to 10.5Mpa. True -- there may be a pressure multiplier here due to the relative size of piston diameters and pipeline internal diameters -- but you get the point, a healthy Pump produces pressure which is way beyond the stopping power of a finger.

If all IS good -- meaning strong flow and pressure -- it is reasonable to assume that the AHC pump sub-assembly is healthy. (Remember that the Pump is a Gear Pump, meaning that it is a positive displacement pump and so fluid has to go somewhere, cannot simply churn inside the Pump -- except maybe if the internal O-rings on the gear carriers inside the Pump have been blown completely, short-circuiting the high pressure and low pressure sides of the pump).

If all IS NOT good -- meaning poor flow and pressure -- then is the problem in the Pump, OR, is there a blockage as you suspect??

Repeat the test -- but this time remove the Pressure Sensor. This creates a parallel exit path for fluid from the AHC Pump.

If there is now good flow and pressure through the exit path provided by removal of the Pressure Sensor, then it is reasonable to assume that the Pump is healthy, and that there is a full or partial blockage or mechanical fault at the Return Valve.

See more at the following links with pictures and video clips, including what to do about the Return Valve (if that is what proves to be the problem -- and if it is, then replacing the AHC Pump sub-assembly 48901-60010 will not overcome an issue with the Return Valve which is situated within the housing 48905-60010):

Post #132
LX470 AHC issues - pressure sensor 1998 Vs. 2002 - https://forum.ih8mud.com/threads/lx470-ahc-issues-pressure-sensor-1998-vs-2002.1267066/page-7#post-15549367

Post #139
LX470 AHC issues - pressure sensor 1998 Vs. 2002 - https://forum.ih8mud.com/threads/lx470-ahc-issues-pressure-sensor-1998-vs-2002.1267066/page-7#post-15553902

Post #140
LX470 AHC issues - pressure sensor 1998 Vs. 2002 - https://forum.ih8mud.com/threads/lx470-ahc-issues-pressure-sensor-1998-vs-2002.1267066/page-7#post-15554138

@IndroCruise Holy moly, thanks for the quick reply. There's SOOOO much information here, it's a bit overwhelming and hard to parse through. It seems I have a similar issue as suprasvobodea - I had seen their other thread, but not this one, so thanks for pointing me in this direction. I will remove PS and bench test again. Thanks again for sharing your knowledge so patiently.

 

[LX470YYC]

Update - I'll try to use this thread as a notebook going forward in case it can be useful to anyone else trying to maintain their AHC system in the future.

First, tying up the above question - There was a blockage somewhere in the return valve.
- With Fluid Pressure Switch installed, no flow at assembly output
- With FPS removed, reasonable flow at FPS opening
- Blasted back side of return valve with cleaner, may have seen something dark fly out.
- Retest fully assembled, and a good jet of fluid at pump output.

Thank you @IndroCruise for the help with diagnosing the pump.

----------------

So, reinstalled pump assembly in vehicle, ran pump off battery a number of times, heard a lot of gurgling in reservoir, then cleared DTC1762 and have been able to start bleeding using active test for the last few hours. Vehicle currently raises to about 1" below "N" before pump runs out of steam and I bleed.

Done for the night - maybe tomorrow some more bubbles will have worked themselves into a bleedable location.

Next post will provide background (as best I can remember) for the last few weeks leading up to this point.

 

[suprarx7nut]

@LX470YYC , @suprasvobodea and @IndroCruise awesome work on this. It seems you've uncovered a trending failure mode. Well done!

The community knowledge base continues to grow!

 

[LX470YYC]

AHC Issues Background - 2003 LX470, 206,000KM

(DD/MM/YY)
15/07/24
- Loaded truck for a camping trip and truck wouldn't raise to H. (Truck was definitely overweight) Started researching options to increase load ability and refresh AHC.

06/08/24
- Installed KTRS-79s
- Cross-Levelled and did overall health check of AHC using @suprarx7nut (YotaMD)'s Youtube video and cheat sheet.
- Before King Springs and Cross Level - Front Pressure 8.0, Rear Pressure 7.6, Gradations = 7.
- Results after King Springs: Front Heights - 19.5", Rear Heights - 20.5", Front Pressure 6.9, Rear Pressure 6.0, gradations increased to about 10.
- Smile on face for about an hour, as System worked as expected and King Springs stiffened rear end
- First Issue started here, while fine tuning the front height. This is before "opening" anything up. Hadn't changed fluid or removed/disassembled pump.
- At this point truck wouldn't reach "H", but wasn't throwing codes.
- At some point noticed that reservoir was now overfull. (hypothesis - some part of system starved for fluid, whether with air or blockage)
- Hypothesis 1 - repeated use during tuning loosened crud and clogged strainers.
- Hypothesis 2 - repeated use caused weakened O-Rings in pump sub-assembly.
- Brain issue at one point - Got my righty-tighty messed up on the right torsion bar and took 4 turns counter clockwise, realized mistake after test drive and corrected.
- Never got to Sensor adjustment because issue arose, so TS height is slightly out of spec (0.3")

10/08/24
- Changed AHC fluid (OEM). Existing fluid was BLACK, suggesting extreme negligence (I've owned truck for 6 months)
- Changed Globes for new (not OEM, too expensive)
- Disassembled and cleaned sub-assembly. Lots of small black particles, no gunk. Did not realize at this point that there is a 3rd strainer in return valve, so did not clean.
- Broke accumulator bleeder (F@&K!)
- Filled and cycled L-N-L a number of times and bled all corners (not accumulator)
- Result: Smile on Face. Everything worked well for about an hour.
- Memory becomes a bit foggy here. (rage fog) As truck began to struggle to raise, eventually ending up on the bumb stops with persistent DTC1762.

11/08/24-13/08/24
- Spent time diagnosing no flow pump
- with @IndroCruise help, found likely clogged strainer at return valve, cleaned
- ran pump w/ direct 12v until wires hot. Lots of gurgles in reservoir.
- Was able to clear persistent DTC1762 and use active test to raise/lower/bleed right rear. Have run at least 4l through RR bleeder.
- Pump WILL NOT run continuously with 12V directly applied. Not sure if this Normal Operation. When applying 12V, pump will run for about 1sec a few times before wires become too hot, and pump stops. (@IndroCruise @suprarx7nut can you speak to this at all?)

Current State (14/08/24)
- Truck will raise to about 1" below N.
- During active test, pump makes whining noises that change with varied load.
- Haven't seen an air bubble in the last 1L of bleed.

Current hypotheses:
1) Pump sub-assembly worn (suspect O-rings?) or incorrectly assembled. Notch is correctly oriented to inlet side, but some have noted that even gear tooth meshing (and right/left gear installation) might matter. I find this hard to believe since the gears look utterly identical, but cannot disprove.
2) Persistent air bubble. Not sure if I should suspect accumulator with broken bleeder or bleed at attenuator?

To Test:
1) Replace sub-assembly. New OEM on order from Impex. Likely 2 weeks out. (Japan on Holidays currently)
2) Not sure what to do about Accumulator. Remember @suprasvobodea mentioning something about applying 12V direct, so will look into that.
3) Will look at possible bleed at attenuator.

 

[IndroCruise]

- Pump WILL NOT run continuously with 12V directly applied. Not sure if this Normal Operation. When applying 12V, pump will run for about 1sec a few times before wires become too hot, and pump stops.

You are learning fast and on the right track!!

Please reveiw the hydraulic circuit in my previous post in this thread.

Suggest (strongly) DO NOT run the AHC Pump directly from 12volt supply for more than a few seconds UNLESS very sure that at least one of the Levelling Valves is open inside the Control Valve Assembly. This is necessary to allow fluid to flow to or from the 'shock absorbers' and 'globes'. The point is that the Levelling Valves act as check valves (prevent fluid flow) and are 'normally closed' -- meaning that the Levelling Valves are closed unless specifically opened by the ECU. This is how a healthy vehicle holds its height. The ECU will not open the Levelling Valves in the presence of DTC C1762 or various other fluid pressure-related DTC's.

Operating AHC Pump against closed Levelling Valves means that the fluid has nowhere to go, cannot raise the vehicle, and, as best I understand from comments elsewhere from @Moridinbg, fluid cannot exit through bleeder valves even if they are open when the Levelling Valves are closed.

Operating a pump against closed valves is called 'dead-heading'. In a gear pump -- which is a positive displacement pump -- the fluid MUST go somewhere, OR, the Pump stalls (which causes very high motor currents and very hot leads, AND/OR the pump bursts the seals between the high pressure side of the pump and the low pressure side of the pump.

In the case of this Toyota/Lexus AHC gear pump, the seals are the o-rings on the internal gear-cases and/or the almost-triangular (actually a pentagon -- five-sided) seal on the underside of the pump cover-plate. The gears also will be forced toward the walls roof and floor of the pump casing, causing some wear (and loss of performance) if the condition is sustained.

Leaking fluid from the AHC Pump sub-assembly will not be seen because it remains behind the outer cover of the overall assembly (with the big + on it). There will be a very unhappy sounding pump -- heavy cavitation -- and also turbulence in the AHC Tank as fluid tries to recirculate. The hot motor leads eventually will melt -- and happily in that way act as a 'fuse' before anything too dramatic happens.

In industrial scale gear pumps there is a relief valve to prevent the actual pump case from bursting if sufficient power is applied or valves are mistakenly closed against the operation pump, causing 'dead-heading'.

For the AHC Pump, the Toyota engineers adopted the various DTC settings which include very short response times as the means of protection -- no relief valve -- probably done for simplicity and to reduce the size of the overall assembly. Hence the use of the words "fail safe function" in the AHC Diagnostics section of the FSM in relation to the various different DTC's relating to the AHC Pump and AHC system pressures.

More later on the other matters raised .....

 

[suprasvobodea]

Hello All. Currently trying to diagnose a persistent DTC1762 on my 2003 LX470. Lots of diagnostic history I can share at some point, but right now I'd like to see if anyone has any input specifically on getting flow from the pump assembly.

I've pulled the pump assembly and have bench tested it (Fill reservoir with fluid and apply 12v to motor), with consistent result of zero flow at the output. Motor is good, pump sub assembly seems good as well (gears turn well under bench test, strainers in sub assembly are clean and can be "blown" through). O-rings need a refresh, but their condition along with the nature of the malfunction's progression suggest they're not to blame (happy to have that assumption unlearned though).

My question to limit scope of discussion at this point, is - what are the odds of a blockage within the pump housing between the points marked in the photo, and if possible, how would I go about clearing? It seems that the valve and or the fluid pressure sensor restrict flow on this "high pressure" side of the assembly... can I safely remove the FPS and valve to inspect/clean?

I can't think of many good reasons why a bench test like this would result in NO flow other than a blockage here. What am I missing?

I have a new sub assembly on order from impex, but in the meantime waiting for it, I'd like to make sure I rule out a blockage in what seems like the logical location, and obviously don't want to replace the entire pump/motor due to cost.

TIA.

View attachment 3701280

WOW! ... This sounds like the 5-month nightmare I just put to rest. ! I will write a FULL, picturesque, DETAILED account of it shortly, but to
pay if forward " immediately, I will share the answer to my issue with you. I have the same truck you do ( LX-470 -2002) with 240K miles, always driven in Dallas TX. ( NO SALT!) . I'll make this simple and short now.

1. If you haven't already done so, when the whole assy is removed from its mounting position, set it on the front of the LX ( on cardboard or towel) to test it. The tank should still be attached with some oil in it. Put a small rubber stopper or plug in the outlet so it doesn't leak oil while testing the assy.
2. Remove the PS and apply 12 V directly to the pump.( only a few seconds) It should shoot out a strong stream of oil .
3. Replace PS and remove the plug-in the outlet. Cover the outlet with a finger, and apply 12 V for few sec to pump. IF YOU CAN PREVENT OIL FROM COMING OUT, .... YOUR RETURN VALVE IS PLUGGED !! END OF DISCUSSION. You now must remove it, to clean it. It does have a small particle of something in it that is preventing it from functioning.
4. Check this string several posts back, where INDOCRUSIE sent me pictures and even a video in Russian on HOW to remove it. & then Dissasemble it . ( this I never would have known unless I watched this Russian show about how he did it. ) I will post this story for you and anyone else in the future, but I just don't have 2 hours now to do so. Call me tomorrow at 972-333-0899 if you still are stuck and I will try to help you. We all do much better when we TALK to each other to clarify questions immediately and avoid frustration. I can help you get your LX fixed and working again. Believe me.... after 6 months of trial , and error, communication through this medium with people from ALL OVER THE WORLD - especially Austrail with the GOD-- INDOCRUISE ... My LX , with all NEW: globes, accumulator, pump, PS, rides like a brand new vehicle again! & it was all WORTH IT!

 

[LX470YYC]

You are learning fast and on the right track!!

Please reveiw the hydraulic circuit in my previous post in this thread.

Suggest (strongly) DO NOT run the AHC Pump directly from 12volt supply for more than a few seconds UNLESS very sure that at least one of the Levelling Valves is open inside the Control Valve Assembly. This is necessary to allow fluid to flow to or from the 'shock absorbers' and 'globes'. The point is that the Levelling Valves act as check valves (prevent fluid flow) and are 'normally closed' -- meaning that the Levelling Valves are closed unless specifically opened by the ECU. This is how a healthy vehicle holds its height. The ECU will not open the Levelling Valves in the presence of DTC C1762 or various other fluid pressure-related DTC's.

View attachment 3702301

Operatying AHC Pump against closed Levelling Valves means that the fluid has nowhere to go, cannot raise the vehicle, and, as best I understand from comments elsewhere from @Moridinbg, fluid cannot exit through bleeder valves even if they are open when the Levelling Valves are closed.

Operating a pump against closed valves is called 'dead-heading'. In a gear pump -- which is a positive displacement pump -- the fluid MUST go somewhere, OR, the Pump stalls (which causes very high motor currents and very hot leads, AND/OR the pump bursts the seals between the high pressure side of the pump and the low pressure side of the pump.

In the case of this gear pump, this means the o-rings on the internal gear-cases and/or the almost-triangular seal on the underside of the pump cover-plate. The gears also will be forced toward the walls roof and floor of the pump casing, causing some wear (and loss of performance) if the condition is sustained.

Leaking fluid from the AHC Pump sub-assembly will not be seen because it remains behind the outer cover of the overall assembly (with the big + on it). There will be a very unhappy sounding pump -- heavy cavitation -- and also turbulence in the AHC Tank as fluid tries to recirculate. The hot motor leads eventually will melt -- and happily in that way act as a 'fuse' before anything too dramatic happens.

In industrial scale gear pumps there is a relief valve to prevent the actual pump case from bursting if sufficient power is applied or valves are mistakenly closed, causing 'dead-heading'.

For the AHC Pump, the Toyota engineers adopted the various DTC settings and very short response times as the means of protection -- no relief valve -- probably done for simplicity and to reduce the size of the overall assembly. Hence the use of the words "fail safe function" in the FSM in relation to the various different DTC's relating to the AHC Pump and AHC system pressures.

More later on the other matters raised .....

This confirms what I suspected, thank you. It may be that my background reading comprehension is bad, but it has previously sounded in other threads as if direct 12V connection to the pump can move fluid, which we know logically that it cannot.

 

[LX470YYC]

WOW! ... This sounds like the 5-month nightmare I just put to rest. ! I will write a FULL, picturesque, DETAILED account of it shortly, but to
pay if forward " immediately, I will share the answer to my issue with you. I have the same truck you do ( LX-470 -2002) with 240K miles, always driven in Dallas TX. ( NO SALT!) . I'll make this simple and short now.

1. If you haven't already done so, when the whole assy is removed from its mounting position, set it on the front of the LX ( on cardboard or towel) to test it. The tank should still be attached with some oil in it. Put a small rubber stopper or plug in the outlet so it doesn't leak oil while testing the assy.
2. Remove the PS and apply 12 V directly to the pump.( only a few seconds) It should shoot out a strong stream of oil .
3. Replace PS and remove the plug-in the outlet. Cover the outlet with a finger, and apply 12 V for few sec to pump. IF YOU CAN PREVENT OIL FROM COMING OUT, .... YOUR RETURN VALVE IS PLUGGED !! END OF DISCUSSION. You now must remove it, to clean it. It does have a small particle of something in it that is preventing it from functioning.
4. Check this string several posts back, where INDOCRUSIE sent me pictures and even a video in Russian on HOW to remove it. & then Dissasemble it . ( this I never would have known unless I watched this Russian show about how he did it. ) I will post this story for you and anyone else in the future, but I just don't have 2 hours now to do so. Call me tomorrow at 972-333-0899 if you still are stuck and I will try to help you. We all do much better when we TALK to each other to clarify questions immediately and avoid frustration. I can help you get your LX fixed and working again. Believe me.... after 6 months of trial , and error, communication through this medium with people from ALL OVER THE WORLD - especially Austrail with the GOD-- INDOCRUISE ... My LX , with all NEW: globes, accumulator, pump, PS, rides like a brand new vehicle again! & it was all WORTH IT!

Thanks for getting in the mix, @suprasvobodea !

I am still throwing DTC1762 today, so I will dis-assemble pump again, including pulling the return valve as shown in the videos, and report back here.

@suprasvobodea , are you running a new "never opened" sub-assembly now?

 

[suprasvobodea]

Thanks for getting in the mix, @suprasvobodea !

I am still throwing DTC1762 today, so I will dis-assemble pump again, including pulling the return valve as shown in the videos, and report back here.

@suprasvobodea , are you running a new "never opened" sub-assembly now?

Yes, I bought a SECOND pump sub -assy and NEVER opened it up... no need to so now I have TWO new pumps.. so if anyone is wanting a new one and don't want to pay $350+ for it, let me know, I have one for sale! It's on EBAY right now.

 

[LX470YYC]

EOD Update:
(TLDR - thought I had it, fecked it up)

- Removed Pump Assembly for another bench test
- Bench test 1, fully assembled. NG. Tiny dribble.
- This is where I screwed up. I didn't first do another bench test with the Pressure Sensor removed to check flow. This would have confirmed sub-assembly operation and 100% confirmed return valve as culprit. Dang it.
- Got myself excited and dismantled the Return Valve as per "Auto-Papa's" Russian Language YouTube Videos.
- Cleaned Return valve. Folks... This needs to be on the list of Must Do AHC maintenance items. It is a tiny, intricate valve with tons of opportunity for clogging, since EVERYTHING coming back to the tank goes through this valve WITHOUT ANY filtering. (correct me if I'm wrong) So, any sludge returning to the tank has to clear this ABSOLUTELY minuscule valve. Next post will show photos of Return Valve removal, cleaning etc.
- Re-assembled, bench tested and a MASSIVE JET of flow. Felt good, felt promising.
- The other mistake though - is that along with not checking flow before the Return Valve by first removing the Pressure Sensor, I also fiddled with the sub-assembly. I wanted to triple confirm that I had installed all the parts (O-rings/bearing races) correctly. So, it is possible that by re-assembling the sub-assembly (again) I may have inadvertently temporarilt fixed a weak point (re-seated a leaky o-ring, etc)
- Re-installed on Truck, and was nearly instantly rewarded with pressures of 3.1 (F), 3.6 (R) and 7.1 (A).
- Pressures went as high as 4.1 (F), 4.7 (R) and 10.1 (A).

- Here's were I lost the plot. Those were the best numbers I got, and I would say (foggy memory) that the whining of the pump got worse and more consistently loud as the day progressed (bleeding for a number of hours).
- And this is where I ended the day. Pressure numbers of 2.9 (F), 2.1 (R) and 7.0 (A) or worse, and lots of whining... from the truck... and maybe from me as well.

Tomorrow I will pull the outlet line from the pump and check pressure again. If weak, I will remove and bench test again, properly this time confirming whether return valve is blockage or sub assembly is weak.

Next Post - Detailed photos of return valve removal/cleaning.

 

[LX470YYC]

AHC Housing - Return Valve Removal, Inspection and Cleaning:

Assuming that by the time you read this post, you already know how to remove the pump from the car, test the sub-assembly's function, and dismantle the various parts.

Pump Flow before:

1) Using a #8 wood screw turned in the the strainer, gently pry the Return Valve up using pliers.

2) Remove O-ring from wide end and "roll" the end cap fitting out using a slightly larger diameter screwdriver or pick and a hammer.

3) Pry end-cap fitting out gently with a small screw driver

4) Inspect and Clean Valve Internals. There is an unbelievably small spring and ball bearing inside this piece, which in my case were definitely gummy and cruddy. You can barely make out the spring and bearing inside the hole.

Continue Next Post:

 

[LX470YYC]

5) Might as well remove the strainer from the narrow end of the valve as well and blast it.

6) Pump output after cleaning the Return Valve.

 

[LX470YYC]

Happy to report - Problem seems to be solved. Reserving judgement for a few days to see if it holds out.

Journaled here in hopes that someone else might find the troubleshooting sequence useful.

Today's Work:
- Bench tested AHC pump assembly - NG. (almost zero flow)
- Removed Pressure Sensor - NG (Almost zero flow)
- Above was new information. I had been operating on the assumption that the sub-assembly was solid because it had tested well previously (after removing/cleaning Return Valve)
- So, dis-assembled the Sub-assembly, slowly, taking pictures, then compared to both the photo's I have seen at this thread (thanks to @BullElk for the writeup here):
AHC pump removal with pics - https://forum.ih8mud.com/threads/ahc-pump-removal-with-pics.1227554/
and in "Auto-Papa's" youtube videos:


Problem is, in both those examples it's very hard to see how the dual o-ring/spacers are stacked up, and being an idiot, I never took pictures of it the first time I cracked it open (which, I'm sure has been the end of many of these units!) It has always looked to me as though the o-rings touched the back of the bearings and the spacers touched the sub-assembly "cap". In fact, as I look at the second "white paper" that @IndroCruise put together (post #12 in BullElks teardown thread), it still looks that way, even though it's very hard to tell by any of these photos.

Well, here is why I'm reserving judgement. Because I have intentionally installed those two elements the opposite way than I had previously. Spacers touching back of bearings, and o-rings touching the sub-assembly cap.

Right or wrong, between building the sub-assembly this way, and another solid round of cleaning strainers and the return valve, I'm up and running, with fully functional AHC - didn't even have to bleed it!

My takeaway and teachable moment from this experience is - just take the damn photos and write down the damn sequence. You might think it's not worth the time. But if you get something small wrong (like the orientation of a couple o-rings) it could waste 3 full days of your life. It's worth the extra hour documenting disassembly.

So, final diagnosis of the problems seems:
- Repeated use during original cross-leveling and pressure checks after King Springs loosened a lot of particles into AHC fluid. I actually found something resembling a small hair ball in a strainer today. (WHAT!?)
- Strainers clogged, causing AHC to struggle.
- During Globe R&R/Fluid change, strainers cleaned but sub-assembly likely re-assembled incorrectly.
- Repeated attempts to diagnose problem with the old "do all the fixes at once an it'll be faster" fallacy getting in the way of actually isolating the problem, aside from the fact that I do actually think the return valve was clogged at one point, and the strainers clogged again a second time (another reason I'm reserving judgement, they may clog again due to the apparent neglect this system has been subjected to by previous owners).

I have a good photo of the orientation of the o-rings/spacers on the back of the bearings, but I won't post it yet unless the elder statesmen @IndroCruise @suprarx7nut etc can verify that indeed the way I oriented them is correct.

Anyhow, thanks to all for your help in diagnosing and solving this issue. Much appreciated and will be looking for ways to pay it forward.

 

[LX470YYC]

Just a screen cap to document current AHC conditions.

Haven't adjusted the front height sensors yet (they needed some PB Blaster) but fender height is bang on.

Rear Pressure is a bit low - 1/3 tank of fuel and completely unloaded. Loaded for a trip its nearly 1000lb heavier including passengers, so likely closer to spec. (will check next camping trip) Not much I can do about that short of going back to OEM springs, spacers and airbags. King Springs and a slightly stiff ride around town are the compromise for less cost.

 

[MongooseGA]

Huge kudos for putting in all of this work to maintain the AHC system. You're going to love having it run properly.

 

[suprarx7nut]

Happy to report - Problem seems to be solved. Reserving judgement for a few days to see if it holds out.

Journaled here in hopes that someone else might find the troubleshooting sequence useful.

Today's Work:
- Bench tested AHC pump assembly - NG. (almost zero flow)
- Removed Pressure Sensor - NG (Almost zero flow)
- Above was new information. I had been operating on the assumption that the sub-assembly was solid because it had tested well previously (after removing/cleaning Return Valve)
- So, dis-assembled the Sub-assembly, slowly, taking pictures, then compared to both the photo's I have seen at this thread (thanks to @BullElk for the writeup here):
AHC pump removal with pics - https://forum.ih8mud.com/threads/ahc-pump-removal-with-pics.1227554/
and in "Auto-Papa's" youtube videos:


Problem is, in both those examples it's very hard to see how the dual o-ring/spacers are stacked up, and being an idiot, I never took pictures of it the first time I cracked it open (which, I'm sure has been the end of many of these units!) It has always looked to me as though the o-rings touched the back of the bearings and the spacers touched the sub-assembly "cap". In fact, as I look at the second "white paper" that @IndroCruise put together (post #12 in BullElks teardown thread), it still looks that way, even though it's very hard to tell by any of these photos.

Well, here is why I'm reserving judgement. Because I have intentionally installed those two elements the opposite way than I had previously. Spacers touching back of bearings, and o-rings touching the sub-assembly cap.

Right or wrong, between building the sub-assembly this way, and another solid round of cleaning strainers and the return valve, I'm up and running, with fully functional AHC - didn't even have to bleed it!

My takeaway and teachable moment from this experience is - just take the damn photos and write down the damn sequence. You might think it's not worth the time. But if you get something small wrong (like the orientation of a couple o-rings) it could waste 3 full days of your life. It's worth the extra hour documenting disassembly.

So, final diagnosis of the problems seems:
- Repeated use during original cross-leveling and pressure checks after King Springs loosened a lot of particles into AHC fluid. I actually found something resembling a small hair ball in a strainer today. (WHAT!?)
- Strainers clogged, causing AHC to struggle.
- During Globe R&R/Fluid change, strainers cleaned but sub-assembly likely re-assembled incorrectly.
- Repeated attempts to diagnose problem with the old "do all the fixes at once an it'll be faster" fallacy getting in the way of actually isolating the problem, aside from the fact that I do actually think the return valve was clogged at one point, and the strainers clogged again a second time (another reason I'm reserving judgement, they may clog again due to the apparent neglect this system has been subjected to by previous owners).

I have a good photo of the orientation of the o-rings/spacers on the back of the bearings, but I won't post it yet unless the elder statesmen @IndroCruise @suprarx7nut etc can verify that indeed the way I oriented them is correct.

Anyhow, thanks to all for your help in diagnosing and solving this issue. Much appreciated and will be looking for ways to pay it forward.

Annoyingly, my pictures from my pump-opening session don't show anything helpful. Sorry!

I can vouch for the extreme helpfulness of pictures, though. I started taking pictures and video to post on Youtube. I stopped that a long time ago, but still take tons and tons for my own sanity. Where that nut go? Does that bracket go on now or in two steps? Oring above or below? etc...