Hi everyone, today after a long time I checked the fuel system with vcds, the problem is that the car shuts off after a few minutes, I already replaced :
(high pressure fuel pumps, injectors, coils, spark plugs, intake manifold, vvt,timing chains)
after all this the result was very similar and did not change. Today I checked the pressure of the rear fuel pumps and the high pressure fuel pumps.


When you press the gas, the pressure drops to about 5 bar, When the car is idle the pressure is about 5.3 in the rear pumps.
In the high pressure pumps when you press the gas, the pressure rises to 8 bar, The pressure is about 6 or 5.5 bar when the car is idling although it is still very low Do you think that replacing the rear pumps and the fuel filter will solve the problem?

 

Please copy and paste the error codes you’re getting.

 

005715 - Please check DTC Memory of ABS Controller
P1653 - 008 -
Freeze Frame:
Fault Status: 01101000
Fault Priority: 2
Fault Frequency: 2
Reset counter: 255
Mileage: 305834 km
Time Indication: 0
Date: 2023.11.05
Time: 00:12:06

Freeze Frame:
RPM: 0 /min
Load: 0.0 %
Speed: 0.0 km/h
Temperature: 24.0°C
Temperature: 26.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 11.557 V

000135 - Fuel Rail/System Pressure
P0087 - 002 - Too Low - Intermittent
Freeze Frame:
Fault Status: 00110010
Fault Priority: 2
Fault Frequency: 1
Reset counter: 255
Mileage: 305834 km
Time Indication: 0
Date: 2023.11.05
Time: 00:12:10

Freeze Frame:
RPM: 643 /min
Load: 49.0 %
Speed: 0.0 km/h
Temperature: 24.0°C
Temperature: 23.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 12.446 V

 

000135 - Fuel Rail/System Pressure
P0087 - 002 - Too Low - Intermittent

This is the only fault you’re getting?

This is the high pressure side, so something still very wrong with it. The pressures are way too low. Should be at least 30 Bar (120 Bar WOT). Maybe a leak, stuck injector, blockage, bad HPFP’s, etc. Bad HPFP’s are the most common fault here.


Low pressure side of around 5 bar is normal. And if it weren’t, there would be a fault code logged as the pressure is monitored.

 

I agree with you, the high pressure pumps are known to be the most common problem for this, that's why I replaced them and all the injectors but the problem still exists, is it normal if the rear pumps lose pressure while pressing the gas pedal (less than 5 bar)? Maybe only the filter under the car is the problem ?

 

5.3 bar to 5 bar on the low side is not a significant drop and I would say normal performance. But changing the filter would be advisable if you haven’t done so yet.

Where did you get the replacement HPFP’s from? Are they the correct ones? Do you still have the old ones? How do they perform?

 

Thanks for the help
The HPFP are original from Audi, I took them from the same engine that works normally from the same type of car (a8), I don't get a fault on them in the vcds. I still have the old pumps on which I didn't get a vcds fault either but I thought they were tired already and should be replaced as you said it is known to be a common problem with low fuel pressure.

 

Ok. About the only thing you haven’t replaced is the fuel rail pressure regulator valve. If that’s stuck open, that could be the cause.
Part no: 06D130757C

 

Thanks . I will check and update if this is the problem.