A Different Fuel Pump Relay Experience & Education (Long) (1 Viewer)

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In the hope it helps, I thought that I'd share something I recently experienced. Recently my rig started surging on prolonged aggressive accelerations. I checked all common things (electrical connections, vacuum connections, intake, exhaust, computer codes, scanner stuff, etc.) and found nothing of note. Then I checked less common things like loose linkages, accelerator cables, transmission cables, fuel filter, fuel pump, etc and everything seemed excellent. The only thing observably different was sporadically slightly leaner AFR's of 11.0 to 11.6 on prolonged aggressive accelerations instead of the typical 10.0 to 10.8. Of extra interest in my mind was that the transition from closed loop to open loop was the typical instant 12.8, then 12.6, then 12.4 etc as always.

I was almost at a loss for a few weeks until one day during traffic the rig shuttered and stalled. I then suspected the Fuel Pump Relay. Luckily the rig started right up. I went to work and then later took her home and cleaned the contacts of the relay with contact cleaner. I wanted to avoid at first the filing trick others have had success with simply because I basically think that the contacts should stay sharp and not be blunted by filing. (Its an OCD thing not to suggest that filing won't work.) Well the contact cleaner helped somewhat but still had surging during aggressive acceleration. I immediately resolved to replace the relay and was almost completely confident that the stalling wouldn't appear again for the few days it took to receive the relay.

Meanwhile I noticed that nearly every time the rig surged faster the wideband was reading 11.0 to 11.6 and that every time the rig surged slower (is that the right way to say something surged?) it read its regular 10.0 to 10.8! After observing this over and over I felt like I stumbled onto something rather significant with a Fuel Pump Relay that was just failing just enough to lean the mix a little at acceleration. The point to this is that this is another example of our rigs running stronger with slightly leaner AFR's.

My understanding from using Toyota texts is that "when the engine is cranked or operated at high speed and/or heavy load, the ECU turns off TR1 closing contact A of the Fuel Pump Control Relay. This allows current to flow directly to the fuel pump, causing it to run at high speed. " whereas "under all other operating conditions, the ECU turns on TR1, which energizes the Fuel Pump Control Relay. This closes relay contact B and forces current to flow through the resistor, causing the pump to run at low speed." I can only conclude that a rapid on-and-off of this cycle caused the surging. Since the default to relay is going through the resistor I am assuming that the ECU rapidly and repeatedly tried to close contact A but the relay could not consistently maintain that mode and then that the default rapidly and repeatedly activated. I'm not sure how to test that assumption but one thing that is clear was that the rig ran stronger for the few seconds it was a little leaner.

Now the next thing on my mind is if its actually possible that with the fuel pump pumping in "slow mode" the rig can really still maintain an AFR of 11.2 !?! That would be absolutely astounding to me. What I think is much more likely is that as soon as contact A closed again the fuel pump fully spun up and rapidly recovered the leaning AFR. I'm not really willing to test this theory but it is something to think through and it is easy enough to test for someone much more daring than me! If there really is enough headroom that the stock fuel pump can provide AFR's of 11.2 on a Forced Induction rig when still in slow mode I'd be absolutely astounded. Even if not, the fact that WOT richens to 10.0 with a stock MAF and 10.8 with the LT MAF and the fact that 10.8 runs stronger than 10.0 and 11.6 runs stronger than 10.8 shows me that these rigs have huge headroom from a fueling perspective, that they like things leaner to a proper point, and that I now need to add an Exhaust Gas Temperature sensor to see if the little leaner operation is increasing exhaust temps too much and then finally to add more air via more boost and continue to test the theory of optimal AFR's for performance and for safety. Stay tuned (pun intended). :cheers:
 
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landtank

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The 10.8 AFR that people have reported with my MAF is generally considered "rich" when tuning for performance but is also considered to have a safe margin concerning running too lean and high EGTs.

What I would suggest is to monitor the fuel rail pressure during those high load/WOT times. It's possible that the fuel pump during those times is overwhelming the FPR or the return line causing an increase of pressure which in turn would richen the mixture.

If that is the case then looking into better managing the fuel rail pressure at WOT would make sense.

Also, while your wideband reported an AFR of 10.0 (which is it's limit) with the stock MAF, people with the innovate unit are reading 8.6 AFR. Something to consider when judging performance increases.
 

landtank

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Another thought Shawn is that you should clean the MAF sensor.

I looked at a friend's Mom's RX300 last week that had a CEL light on. The code was misfires on cylinders 3 and 4.

I pulled the MAF sensor which happens to be the one I spec for my housing and it was filthy. All I had was some Isopropyl Alcohol 91%. Using that and a small artist round paint brush I cleaned both the IAT and MAF sensors.

After installing the cleaned sensor I saw 6% shift in the LTFT% leaning out the mixture now that the sensor was seeing more air.

You don't want to run a K&N, TRD or similar oil type filter and keep up with your filter changes and make sure the wing nut on the cover is in place. That nut has a gasket on it and if not used unfiltered air will enter the system.
 
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Right, but the new Fuel Pump Relay fixed all the problems that I mentioned. Now I need to just tune for better fuel delivery. 8.6 is incredibly rich. I knew that my wideband wasn't reading past 10.0 but 8.6 holy moly!!! Your MAF at 10.8 is an incredibly awesome improvement over 8.6; at 8.6 we are all throwing away alot of fuel and power! I think that 11.0 to 11.5 is ideal and super safe although I am planning to put the EGT sensor on to verify that first. Anyways, like I wrote, none of this was due to the stock MAF or to your MAF (tried them both through this relay thing) being dirty; it was due to the Fuel Pump Relay alone as far as I am seeing. :cheers:

Ohh, I have never used and will never use the K&N. :cheers:
 

landtank

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If the fuel pump relay fixed the problem then it's possible that with full 12v it's overwhelming the FPR system and the rail pressure is increasing beyond the stock set point.

The idea is to pump fuel into the rail at a rate where it exceeds demand but not so much that the excess can't be bleed off and returned to the fuel tank.

From memory of other posts of your's this is very likely. You've mentioned that at some point the AFR spikes and then slowly continues to increase rich to a point where it stabilizes. I would be inclined to think that the spike is the pump being switched to the high side and then the slow increase is the system stabilizing at a new higher pressure.

This does happen when people put in monster fuel pumps and don't increase the return line. The too small return line acts like a restrictor and the back up results in a too high fuel rail pressure producing a rich condition.

If this condition can be determined to be the case a simple fix is to add another resistor to the high side of the relay to drop the pumps output to where it doesn't overwhelm the system and maintains proper fuel rail pressure.
 
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If the fuel pump relay fixed the problem then it's possible that with full 12v it's overwhelming the FPR system and the rail pressure is increasing beyond the stock set point.

The idea is to pump fuel into the rail at a rate where it exceeds demand but not so much that the excess can't be bleed off and returned to the fuel tank.

From memory of other posts of your's this is very likely. You've mentioned that at some point the AFR spikes and then slowly continues to increase rich to a point where it stabilizes. I would be inclined to think that the spike is the pump being switched to the high side and then the slow increase is the system stabilizing at a new higher pressure.

This does happen when people put in monster fuel pumps and don't increase the return line. The too small return line acts like a restrictor and the back up results in a too high fuel rail pressure producing a rich condition.

If this condition can be determined to be the case a simple fix is to add another resistor to the high side of the relay to drop the pumps output to where it doesn't overwhelm the system and maintains proper fuel rail pressure.

Yes more and more I think that this has been happening all along and more and more I think that so many scenarios are answered by a fuel pressure gauge permanently installed on the fuel rail.

The "spike" is specifically at the transition to open loop; the rig immediately reads 12.8 AFR and then as the acceleration continues it goes 12.6, 12.4, 12.2 etc until it stabilizes at 10.8 with your MAF and apparently at 8.6 with the stock MAF. It repeats itself this way time after time and I think that the Fuel Pressure Regulator or the Fuel Pressure Return might be merely overwhelmed with fuel. If this is the case it suggest that a rising rate FPR at least with the 95-97 rigs is the wrong way to go (for stockers, SuperChargers, and Safaris). It also suggests that extra injectors or larger injectors at least with the 95-97 rigs is the wrong way to go (again for stockers, SuperChargers, and Safaris). While those three things would relieve the Regulator or Return somewhat they will likely work only to further richen the richness. Again, so many scenarios are answered by a fuel pressure gauge permanently installed on the fuel rail from what I'm seeing.

The "real" question to me then is and has always been ... is it as simple as adding more air via more boost? If that is the case then cranking the boost up is ultimately the easiest most exciting fix for SuperChargers and Safaris. The reason I referenced these three specific setups is that apparently the AVO turbos push enough air to actually overwhelm the headroom we have from a fueling perspective and need either extra injectors or RRFPR's or optionally both (cannot really remember). This hints to me that adding more air to a proper point shifts the balance totally. Sooo, the careful way to work this is add the fuel pressure gauge permanently which will answer all the unanswered things about the stock MAF and the LT MAF, get a good baseline between those two setups and then start slowly upping the boost. If I'm right I'll get to a sweet spot which I think will be between 10 psi and 12 psi with the Safari Turbo System where by AFR's will be right around 11.5 (what I personally predict as ideal) at WOT.

Again, stay tuned! :cheers:
 

landtank

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in my opinion the only way to properly meter fuel is to be able to consistently measure the air intake and have a consistent predictable fuel pressure.

If when the fuel pump relay goes high the rail pressure goes arye then that needs to be addressed prior to increasing boost.
 
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in my opinion the only way to properly meter fuel is to be able to consistently measure the air intake and have a consistent predictable fuel pressure.

If when the fuel pump relay goes high the rail pressure goes arye then that needs to be addressed prior to increasing boost.

I agree with the first point. But, short of sizing down the fuel pump or sizing up the return line, I'm just hoping to use that extra fuel efficiently. What would you suggest for stabilizing the fuel rail pressure given what we've got here? I love this stuff I really love this stuff. :cheers: :cheers: :cheers:
 

landtank

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lowering the pumps output is done through a resistor. Just like the low side, if we need to lower the pump's output on the high side you just add a resistor. Just not as high an ohm value that is on the low side so it's output is increased over the low side but not to a point of overwhelming the regulating system.
 
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lowering the pumps output is done through a resistor. Just like the low side, if we need to lower the pump's output on the high side you just add a resistor. Just not as high an ohm value that is on the low side so it's output is increased over the low side but not to a point of overwhelming the regulating system.

I still think that adding more air via more boost is preferable to finding the perfect AFR's with resistors for the fuel pump's fast mode at my current modest amount of boost. I mean say I find the perfect resistor to get the perfect AFR with my 6 to 8 psi now, then, that's the limit forever more. Whereas if I find that with 10 to 12 psi (12 is the most that I would want to go without bottom end buildups) my AFR at WOT is btwn say 11 and 11.5 and my EGTs are btwn 1300F and 1500F then I'm :D:D:D all the time!

I know that you have always had doubts that it is so simple but btwn the fuel rail pressure problem, the return line volume problem, the evidence that AVO's throw way too much air at the engine due to their sizing, and the evidence that all the SuperCharged and SafariCharged systems are stinkin rich at least as far as 95-97 models go, I think that I can leave the fuel rail pressure problem and the return line volume problem alone and throw much more air at the thing to solve this situation. Do you still think that smaller injectors will help here? I'm thinking that route will only worsen the fuel rail pressure problems and the return line volume problems.

I know we've both looked at this same thing and come with completely different conclusions but I still don't see how anything other than more air and more boost will get me :D:D:D like I would want? The best thing would be to find that at say 10 psi the AFR's are right in range and THEN that adding the Rising Rate Regulator relieves both the rail problem and the return problem and allows another 1 to 2 psi boost. That would be wonderful!

Ohh for anyone reading this, please understand that Rick and I love to debate this stuff tirelessly, it isn't an argument at all, we just love to learn through testing one another's thoughts and theories.
:cheers::cheers::cheers:
 

landtank

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Shawn, the idea of adding more air to lean the AFR is kind of a strange one for me. If you add more air then the MAF will see it and lengthen the injector duty cycle. So you get more fuel as well. How do you figure that this process will lean the AFR?

To alter the AFR any given load you need to alter the amount of fuel. This is why tuners use a programmable piggy back to alter the injector duty cycle or add injectors or use a RRFPR. All of those influence the amount of fuel being delivered.

As for the resistor, I don't think you understand how this works. You want the pump to supply fuel at the highest possible rate for that range of operation but not to the point where the excess can't be reliably bleed off. Exceeding that point will cause a rise in fuel pressure at the rail. This way there is plenty of head room to continue to supply fuel at a greater need. As the need increases less fuel is bleed off but the pressure remains consistent.

We've talked about this adding air thing before and I'm not sure where you got the idea from but I honestly don't see it working out unless you flow so much air that it exceeds the flow of the injectors and then leans out. That's what happens on the 93s and 94s as the duty cycle gets clamped by the ECU and more air leans out the mixture.

Go ahead and try it, but I would proceed with caution.
 
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Shawn, the idea of adding more air to lean the AFR is kind of a strange one for me. If you add more air then the MAF will see it and lengthen the injector duty cycle. So you get more fuel as well. How do you figure that this process will lean the AFR?

To alter the AFR any given load you need to alter the amount of fuel. This is why tuners use a programmable piggy back to alter the injector duty cycle or add injectors or use a RRFPR. All of those influence the amount of fuel being delivered.

As for the resistor, I don't think you understand how this works. You want the pump to supply fuel at the highest possible rate for that range of operation but not to the point where the excess can't be reliably bleed off. Exceeding that point will cause a rise in fuel pressure at the rail. This way there is plenty of head room to continue to supply fuel at a greater need. As the need increases less fuel is bleed off but the pressure remains consistent.

We've talked about this adding air thing before and I'm not sure where you got the idea from but I honestly don't see it working out unless you flow so much air that it exceeds the flow of the injectors and then leans out. That's what happens on the 93s and 94s as the duty cycle gets clamped by the ECU and more air leans out the mixture.

Go ahead and try it, but I would proceed with caution.

My whole thought here is that the injectors' duty is already at max of normal operational limits and that the MAF can't add anymore short of what it would take to throw codes. That may be where I'm wrong but in open loop operation I'm assuming injectors already giving it everything that they've got. So with the first assumption factual or not, is where I'm willing to test theory.

I totally understand the resistor thing I'm just saying that I'm "starting with the end in mind" and for me the end is and has always been more boost. So I don't wanna dick around with perfecting the AFR's at 6 to 8 psi; I want to get to 10 psi minimally and 12 psi preferably. That was the wish all along. All my research so far shows that the drivetrain, the engine and the transmission can capably handle 12psi. Again I'm assuming that the amount of fuel is somewhat static so changing the air is as logical an approach as I can creatively come up with in my mind. The fact that AVO turbos lean these rigs out right away is pretty much proof to me that the transition point from rich to lean is involving of airflow exceeding fuelflow. I don't want to totally transition to that extreme, I just want to get to the sweet spot. I know that you thought smaller injectors were the answer and you even sourced some from somewhere specific but to me that is the opposite solution. Again, I'm starting with the end in mind.

Having a few tools to test the theory would help here. A fuel pressure gauge would help hugely. So would an exhaust temperature gauge. Also knowing exactly what the injector duty cycle currently is would help hugely. If it turns out that injector duty is less than say somewhere around 80% as I run the rig now, well then that changes things totally. But again I'm assuming that I'm at the upper limit of normal operation and that at open loop our injectors are giving it good 80%+ of full open. One thing that's for sure is that AVO turbos are finding the fuel limit via much more air. That alone tell me it is possible, I don't know what other conclusion can be confidently concluded given all the things we see from stock to SC to Safari Turbo to AVO Turbo in order of air, boost and fuel?

Again, for everyone else reading, this is what we do Rick and I, no worries whatsoever except I gotta get off my ass and boost the boost and Rick's gotta get off his ass and finish his fabulous turbo kit. Then we will know that much more! :cheers::cheers::cheers:
 

landtank

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Best of luck with this Shawn. If your correct on this then as soon as you add boost the MAF will saturate and you will see a lean condition. If I'm right then the MAF will continue to read even higher air flow values and it will be more of the same. If we are both wrong it will be something entirely different.

As for the manifold it's inching closer everyday but still no completion date. I did however buy another 80 with a blown motor and have sourced a good motor to rebuild and place into that truck as a turbo platform.

I'm hoping this is the year for it all to come together.
 

landtank

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it occurred to me that if the high side of the relay was the cause for TurboCruiser's problem it would also be a problem for NA trucks. I've only just began to look, but does anyone have an idea how to attach a fuel pressure gauge on our trucks? If I can figure that out I'll start testing the system.
 

sleeoffroad

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You need a double banjo bolt if you want to do it right after the filter, or a special fitting underneath the fuel regulator. But then I thought you guys already did that, because this is what you posted in the big old MAF thread when we discussed how much the fuel pressure went up under boost.

Post 317 "for what it's worth during my testing, applying 8psi to the FPR there was only a 1.5psi increase. Hardly providing a linear pressure differential that has been suggested earlier."

IH8MUD Forums - View Single Post - Landtank MAF surprising scangauge results
 

landtank

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would it be better at the rail itself?

The above info was a calculated value not an exact reading. If the calculated value was any where close I would have assumed it was as you stated.
 
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The above info was a calculated value not an exact reading. If the calculated value was any where close I would have assumed it was as you stated.

Uhh, okay, and uhh again, I thought there was an actual measurement and methodology to those values? :confused::confused::confused:
 

landtank

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I applied 8psi to the diaphragm at idle and watched little change in the FT%. If the system was setup up for a constant pressure differential that 8Psi should have increased the fuel pressure by 8psi which would mean about an 18% increase in differential.

There was a methodology. I'm trained to use on board components to evaluate system performance. It comes from being a field technician and not being able to carry a complete lab with you on a service call.
 

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