LPFP pressure instability suddenly drops, HELP! HELP! HELP!

[zhaijialin]

hello!

my car is B8.5 S5.
My car use IE DP E40 tune（V2.30）.
I upgraded the AUTOTECH HPFP and connected a walbro 525LPH in parallel with the original LPFP（See the picture）.
Walbro525 is controlled by pressure. Start at 7 psi.
148738

Fault phenomenon:
I am performing full throttle acceleration and the output of the LPFP is unstable. Sometimes it can be reduced to 2bar. But sometimes it can stay at 7bar. I have replaced all the pipes and the VDO LPFP（8K0919051AJ）, but the fault still exists. I can't find the problem.
I want to know if this is related to IE adjustment?
Is it possible that my LPFP model selection error? Is the pressure relief valve under the fuel filter automatically relieved? Does anyone know the pressure of the pressure relief valve??

log：
https://datazap.me/u/zhaijialin/v230-e40?log=0&data=1



https://datazap.me/u/zhaijialin/v230-e40?log=1&data=1



【11.06Update】

I did 3 things today.

1. Cancel the vacuum pressure switch and replace it with the manual control switch. Open the walbro525 switch before starting, and start the departure when the LPFP pressure display is about 7000-8000hpa!
result：
The fault did not disappear. However, a rule is found that when the car rises to the second gear, the LPFP pressure will immediately decrease, and the general situation will rise to the third gear and return to normal 6000hpa.
log1：https://datazap.me/u/zhaijialin/v230-e40%E6%8B%86%E7%9C%9F%E7%A9%BA%E5%8E%8B%E5%8A%9B%E 5%BC%80%E5%85%B3?log=0&data=0
log2：https://datazap.me/u/zhaijialin/v230-e40%E6%8B%86%E7%9C%9F%E7%A9%BA%E5%8E%8B%E5%8A%9B%E 5%BC%80%E5%85%B3?log=1&data=0

2. Replace the LPFP and fuel filter of the RS7.
result：
Nothing works. Same as before

log1：https://datazap.me/u/zhaijialin/v230-e40-%E6%8D%A2rs7%E6%B2%B9%E6%B3%B5%E5%92%8C%E6%BB%A4%E 6%B8%85%E5%99%A8?log=0&data=0
log2：https://datazap.me/u/zhaijialin/v230-e40-%E6%8D%A2rs7%E6%B2%B9%E6%B3%B5%E5%92%8C%E6%BB%A4%E 6%B8%85%E5%99%A8?log=1&data=0

3. Disconnect the stock LPFP power cord and use only a pump of walbro525.
result：
Using only walbro525, LPFP pressure will also decrease in 2nd gear. Without the help of stock LPFP, LPFP pressure will be lower, reaching 1000hpa.
Since walbro525 is not controlled by the ECU, he has been working hard all the time. Basically, it can be proved that the oil pressure reduction is independent of the ECU.
But where is my fuel going? ? ? Walbro525 has been working hard all the time! ! !

[bajan01]

Interesting. Are you sure that the Walbro pump hasn’t failed or is failing? I’d post this in the IE FB group as well. I’m working on a similar setup for my SQ5.

[zhaijialin]

Interesting. Are you sure that the Walbro pump hasn’t failed or is failing? I’d post this in the IE FB group as well. I’m working on a similar setup for my SQ5.
Walbro pump is no problem. I used the walbro 450LPH and then replaced the Walbro 525LPH. The phenomenon is the same.

[zhaijialin]

help me！
help me！

[Shane Horning]

I had the same issue at first and it turned out to be a bad walbro. I got a new 525 from ti performance and never had another issue. Did you test and make sure there is power at the pump 100% when wot?

help me！
help me！

[Novarider]

Could the walbro be pushing fuel backwards through the lpfp causing it to cut off?

[bajan01]

Could the walbro be pushing fuel backwards through the lpfp causing it to cut off?

I don’t see anyone using any sort of check valve but everyone is using a t-fitting. I decided to use a y-fitting on mine thinking that it would reduce the chance of fuel making its way back to the factory LPFP. I haven’t installed mine yet so this is just theoretical at this point. [emoji41]

[zhaijialin]

I had the same issue at first and it turned out to be a bad walbro. I got a new 525 from ti performance and never had another issue. Did you test and make sure there is power at the pump 100% when wot?

Walbro is powered on and works fine. Because I can use 525 to pump out the fuel tank.

[zhaijialin]

Could the walbro be pushing fuel backwards through the lpfp causing it to cut off?

I also suspect that there is such a possibility. But I blew my mouth to lpfp, I think lpfp has a non-reverse function. But I am not sure how much pressure lpfp can withstand.

[zhaijialin]

I don’t see anyone using any sort of check valve but everyone is using a t-fitting. I decided to use a y-fitting on mine thinking that it would reduce the chance of fuel making its way back to the factory LPFP. I haven’t installed mine yet so this is just theoretical at this point. [emoji41]

I have now changed the tee joint from T to Y. But it seems to have no effect.

[zhaijialin]

The system can sometimes hold 7bar. I don't think there is any leakage in the pipeline, otherwise there is no way to maintain pressure. Now I suspect that at the 525 start-up moment, due to the relatively high pressure, the fuel filter's pressure relief valve will open to cause a pressure drop. It is also possible that the 525 pressure is too large, causing lpfp to reverse pressure relief.

Definitely not a problem with walbro. Because I changed 2 walbro450, 1 walbro525.

Who knows other possibilities?

[Shane Horning]

Fuel shouldn't be able to reverse thru oem. I had exactly the same issue with mine it would pump fuel fine and half the time 7k pressure but then drop to 2k sometime. Do yourself a favor and throw in another 525 from TI performance and good chance it will fix it.
Ps. Where did you buy your pump from? There are Chinese version of the walbro that costs half of the genuine ones
The system can sometimes hold 7bar. I don't think there is any leakage in the pipeline, otherwise there is no way to maintain pressure. Now I suspect that at the 525 start-up moment, due to the relatively high pressure, the fuel filter's pressure relief valve will open to cause a pressure drop. It is also possible that the 525 pressure is too large, causing lpfp to reverse pressure relief.

Definitely not a problem with walbro. Because I changed 2 walbro450, 1 walbro525.

Who knows other possibilities?

[Shane Horning]

Does it act the same with a full tank fuel? Also there could be a possibility the oem pump check valve is weak?

[bajan01]

Does it act the same with a full tank fuel? Also there could be a possibility the oem pump check valve is weak?

What about the pressure switch? Are you running one and what pressure is it set to activate the Walbro pump?

[zhaijialin]

Fuel shouldn't be able to reverse thru oem. I had exactly the same issue with mine it would pump fuel fine and half the time 7k pressure but then drop to 2k sometime. Do yourself a favor and throw in another 525 from TI performance and good chance it will fix it.
Ps. Where did you buy your pump from? There are Chinese version of the walbro that costs half of the genuine ones

I purchased it at https://walbrofuelpumps.com/walbro-f90000285-fuel-pump-525lph-e85-compatible-tiautomotive-tcd470.html

[zhaijialin]

Does it act the same with a full tank fuel? Also there could be a possibility the oem pump check valve is weak?

I filled the tank with 45 liters of fuel and the same failure occurred.

[zhaijialin]

What about the pressure switch? Are you running one and what pressure is it set to activate the Walbro pump?

I set the pressure switch to 7 psi. I also connected an LED to the positive and negative poles of the pump. I can see if it works.

[Shane Horning]

Ok yes that's the good one . This is one I tried 1st that didn't work
I purchased it at https://walbrofuelpumps.com/walbro-f90000285-fuel-pump-525lph-e85-compatible-tiautomotive-tcd470.html.148973

[zhaijialin]

Ok yes that's the good one . This is one I tried 1st that didn't work .148973

Hahaha Ebay sales are all from China?

[Shane Horning]

Well this sure was!
Hahaha Ebay sales are all from China?

[zhaijialin]

【11.06Update】

I did 3 things today.

1. Cancel the vacuum pressure switch and replace it with the manual control switch. Open the walbro525 switch before starting, and start the departure when the LPFP pressure display is about 7000-8000hpa!
result：
The fault did not disappear. However, a rule is found that when the car rises to the second gear, the LPFP pressure will immediately decrease, and the general situation will rise to the third gear and return to normal 6000hpa.
log1：https://datazap.me/u/zhaijialin/v230...3?log=0&data=0
log2：https://datazap.me/u/zhaijialin/v230...3?log=1&data=0

2. Replace the LPFP and fuel filter of the RS7.
result：
Nothing works. Same as before

log1：https://datazap.me/u/zhaijialin/v230...8?log=0&data=0
log2：https://datazap.me/u/zhaijialin/v230...8?log=1&data=0

3. Disconnect the stock LPFP power cord and use only a pump of walbro525.
result：
Using only walbro525, LPFP pressure will also decrease in 2nd gear. Without the help of stock LPFP, LPFP pressure will be lower, reaching 1000hpa.
Since walbro525 is not controlled by the ECU, he has been working hard all the time. Basically, it can be proved that the oil pressure reduction is independent of the ECU.
But where is my fuel going? ? ? Walbro525 has been working hard all the time! ! !

[Shane Horning]

Something is definitely wrong somewhere. It seems the 525 should keep up by itself.
【11.06Update】

I did 3 things today.

1. Cancel the vacuum pressure switch and replace it with the manual control switch. Open the walbro525 switch before starting, and start the departure when the LPFP pressure display is about 7000-8000hpa!
result：
The fault did not disappear. However, a rule is found that when the car rises to the second gear, the LPFP pressure will immediately decrease, and the general situation will rise to the third gear and return to normal 6000hpa.
log1：https://datazap.me/u/zhaijialin/v230...3?log=0&data=0
log2：https://datazap.me/u/zhaijialin/v230...3?log=1&data=0

2. Replace the LPFP and fuel filter of the RS7.
result：
Nothing works. Same as before

log1：https://datazap.me/u/zhaijialin/v230...8?log=0&data=0
log2：https://datazap.me/u/zhaijialin/v230...8?log=1&data=0

3. Disconnect the stock LPFP power cord and use only a pump of walbro525.
result：
Using only walbro525, LPFP pressure will also decrease in 2nd gear. Without the help of stock LPFP, LPFP pressure will be lower, reaching 1000hpa.
Since walbro525 is not controlled by the ECU, he has been working hard all the time. Basically, it can be proved that the oil pressure reduction is independent of the ECU.
But where is my fuel going? ? ? Walbro525 has been working hard all the time! ! !

[bajan01]

Something is definitely wrong somewhere. It seems the 525 should keep up by itself.

Bad pressure switch on the HPFP side? Did you check all the hose connections in the tank?

[Loe]

Here is my take, your HPFP PWM signal is maxed out at 99.99%, but it's maxed out because there is something off on the LPFP side. Can you do a log where you simply just do normal driving and not wide open? Like start logging when you have the ignition switched to "ON" but not actually start the car, and log about 5-10 mins of driving (warm start preferably).

Also keep in mind that fuel flow and fuel pressures are independent though directly related to each other. Are you feeling anything strange with the car at wide open?

[zhaijialin]

Bad pressure switch on the HPFP side? Did you check all the hose connections in the tank?

I replaced the part code 06E 906051K
I also checked the connection hose and there is no leak. And in addition to the 2nd gear, it can be kept at 6000hpa.

[zhaijialin]

Here is my take, your HPFP PWM signal is maxed out at 99.99%, but it's maxed out because there is something off on the LPFP side. Can you do a log where you simply just do normal driving and not wide open? Like start logging when you have the ignition switched to "ON" but not actually start the car, and log about 5-10 mins of driving (warm start preferably).

Also keep in mind that fuel flow and fuel pressures are independent though directly related to each other. Are you feeling anything strange with the car at wide open?
I am on a business trip now, I will test the log of normal driving after going home.

When the fuel pressure is reduced at full acceleration, the acceleration is weak, and the engine has a strange sound of fuel shortage. The EPC fault lamp is lit. Fault record multi-cylinder does not ignite. Fuel pressure returns to normal, acceleration becomes powerful!

[zhaijialin]

help！

[RWD2quattro]

Questions,

1. How is your Walbro 525 hooked up electrically, are you running in parallel with stock wiring or independent?
2. Have you checked your fuel pump control module?
3. What's your voltage drop across the 525 and stock pump?
4. Any codes?

[kelseysautobody]

I am on a business trip now, I will test the log of normal driving after going home.

When the fuel pressure is reduced at full acceleration, the acceleration is weak, and the engine has a strange sound of fuel shortage. The EPC fault lamp is lit. Fault record multi-cylinder does not ignite. Fuel pressure returns to normal, acceleration becomes powerful!

Is it possible the problem is on the ignition side of things and losing fuel pressure is a result of the EPC fault? I saw you didn't have any timing correction in your logs but what about misfires from a bad spark plug or coil?

[zhaijialin]

Is it possible the problem is on the ignition side of things and losing fuel pressure is a result of the EPC fault? I saw you didn't have any timing correction in your logs but what about misfires from a bad spark plug or coil?

I have replaced the new ignition coil and spark plug. EPC lights up, I think it is caused by the fuel pressure is reduced to 3000hpa.

[zhaijialin]

Questions,

1. How is your Walbro 525 hooked up electrically, are you running in parallel with stock wiring or independent?
2. Have you checked your fuel pump control module?
3. What's your voltage drop across the 525 and stock pump?
4. Any codes?

1.warblo525 is independent power control. Power is supplied to the 525 via a pressure switch control relay. All lines are independent and have nothing to do with LPFP.
2. I replaced the fuel pump controller of the RS7. The same phenomenon
3. Warblo525 works at the same time as the stock LPFP. The fuel pressure can reach 8000hpa when idling, and the fuel pressure may be reduced to 2000hpa only when it is fully accelerated.
4. The fault code does not appear frequently. Only when the fuel pressure is extremely low, the EPC will be illuminated, indicating that the multi-cylinder does not ignite.

[Shane Horning]

1.warblo525 is independent power control. Power is supplied to the 525 via a pressure switch control relay. All lines are independent and have nothing to do with LPFP.
2. I replaced the fuel pump controller of the RS7. The same phenomenon
3. Warblo525 works at the same time as the stock LPFP. The fuel pressure can reach 8000hpa when idling, and the fuel pressure may be reduced to 2000hpa only when it is fully accelerated.
4. The fault code does not appear frequently. Only when the fuel pressure is extremely low, the EPC will be illuminated, indicating that the multi-cylinder does not ignite.Not sure what else to check. Again this issue sounds exactly like the problem I had then I installed another walbro and it fixed it. But I would check voltage at the pump and make sure you have 13 to 14 volts when the lpfp pressure drops


Sent from my SM-G935V using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)

[WeeKenny]

Try a new battery I had an issue on my B7 2.0TFSI where the fuel pressure would sometimes drop off at WOT and it turned out after many logs and replacing of parts that I noticed a correlation between WOT a certain rpm level and battery voltage. Turns out that there is alternator over speed protection so it stops supplying charge

[zhaijialin]

Try a new battery I had an issue on my B7 2.0TFSI where the fuel pressure would sometimes drop off at WOT and it turned out after many logs and replacing of parts that I noticed a correlation between WOT a certain rpm level and battery voltage. Turns out that there is alternator over speed protection so it stops supplying charge

Ok. I really don't pay much attention to the voltage problem. Because I think there is a generator working, there will be no voltage drop. Because my car is mainly used for competition, in order to reduce the weight, I replaced the small battery. I will pay attention to this issue again.

[WeeKenny]

Definitely worth checking as I’m fairly certain the alternator (generator) shuts off under certain conditions.

[zhaijialin]

Definitely worth checking as I’m fairly certain the alternator (generator) shuts off under certain conditions.
I just changed a new battery, but the fault did not disappear, it does not seem to be a voltage problem. Next, I plan to connect directly to the HPFP with a small racing fuel tank and an external 044 fuel pump. No longer use stock fuel system.

[Loe]

I dont' recall anyone successfully running a side-strapped 525lph successfully, I could be wrong as I've been out of the scene. It was simply too much fuel at wide-open

[bajan01]

I dont' recall anyone successfully running a side-strapped 525lph successfully, I could be wrong as I've been out of the scene. It was simply too much fuel at wide-open

I hope to be the third person that I know to do so. I’ll know tomorrow. [emoji2958]

[zhaijialin]

I dont' recall anyone successfully running a side-strapped 525lph successfully, I could be wrong as I've been out of the scene. It was simply too much fuel at wide-open

It seems that I have never been successful with RS7lpfp, stock side-450lph or stock side-525lph.

[bajan01]

It seems that I have never been successful with RS7lpfp, stock side-450lph or stock side-525lph.

Are you just using the 525 to fill the bucket then?

[zhaijialin]

Are you just using the 525 to fill the bucket then?

side-strapped 525