A6 3.0 Biturbo P0087 - Insufficient fuel rail pressure

Last edited on 13-06-2021, 15:56, edited 1 time in total.

"I have an A6 CQBC here. The injector for cylinder 2 was replaced due to this error (P0087). After the replacement, the error code P2149 00 [232] appeared, which indicates a fault with the fuel injector(s) bank B - interruption. The owner then brought the car to me. I used an oscilloscope and a clamp meter to check the injector cables, and I observed that when the bank was deactivated, the fourth injector was drawing too much current."
Okay, I replaced injector 4. During the test drive, he disabled another bank, but this time it was bank B. Subsequently, I replaced injector 3 and then injector 1.

Now the supply voltage error no longer appears, but the rail pressure is too low.
I then measured the return flow rate at idle, but they were all pretty much the same, with cylinder 5 showing a slightly higher value.

The fuel injection quantity deviation for cylinder 5 is 5mg per injection, which is too high. Should I replace this injector as well? Or is the problem actually with the high-pressure pump? Could the pressure relief valve in the return line also be defective?

Thank you.
Address 01: Engine Control Module
Label file: Redirection failed!
Control unit part number: 4G0 907 589 A. Hardware: 4G0 907 589.
Component and/or version: 3.0BTD EDC17 H21 0004
Encoding: 0A2A401A056601020000
Operating number: WSC 02391 785 00200
ASAM Dataset: EV_ECM30BTD0114G0907589A 001005 (AU57)
ROD: EV_ECM30BTD0114G0907589A.rod
VCID: B2285C25E5B3021B85-80E6
Sure, here is the translation of the text from German to English:

"1 error found:"

5211 - Fuel system (bank 1): Rail/system pressure too low.
P0087 00 [101] - -
unconfirmed - checked since last deletion.
Environmental conditions:
Error status: 00000001
Error priority: 2
Error frequency: 1
Mileage: 166,431 km
Date: 2021.06.12
Time: 21:05:49

Motor speed: 3056.50 rpm.
Normalized load value: 99.6%
Vehicle speed: 123 km/h
Coolant temperature: 75 °C
Intake air temperature: 32 °C
Atmospheric pressure: 980 millibars.
Voltage at terminal 30: 14.180 V.
Lost count after OBD: 80
Fuel temperature: 35.3 °C
Average injection amount: 84.53 mg/stroke.
Rail pressure regulation: Status bits 0-7: 00000101.
Fuel high pressure: Actual value: 1.6492e+006 hPa.
Fuel high pressure: Target value: 2,000,000 hPa.
Adaptation factor of the pressure regulating valve: 1.0184.
Fuel level: 9.00 liters.

Last edited on 13-06-2021, 17:15, edited 1 time in total.

Hello,

Unfortunately, I can't really give you any specific advice about that engine.

Quote:

The fuel injection quantity deviation for cylinder 5 is 5mg/stroke, which is too high. Should I replace this injector as well? Or is it possibly due to the high-pressure pump? Could the pressure relief valve in the return line also be defective?

If the pressure relief valve is separate from the injector, I would start by swapping the one from cylinder 5 with another one to see if the deviation in fuel injection volume follows the valve.

Generally, the fuel consumption of this engine at full throttle is not insignificant, so I imagine that a clogged diesel filter, blocked intake manifolds, or blocked fuel tank vents could quickly lead to pressure differences in the fuel system.

Best regards, Rainer.

At idle, cylinder five is showing 0.89 mg/hour. I use the 5mg dosage when the idle speed is too high.

I was also thinking about the fuel filter.

He only does it when I'm driving at full throttle; I don't have any problems when I drive normally.

dieselschrauber · Last edited on 13-06-2021, 18:32, edited 1 time in total.

I've temporarily limited the rail pressure to 1800 bar, and it's working fine now, so I don't think the high-pressure pump is the problem. He doesn't do it as often anymore, but he still does sometimes.

dieselschrauber

It seems to be working again, but I'm not entirely convinced yet.

I've also replaced injectors 5 and 6, so now they're all new.
The 5th injector was missing its sealing ring, which is why there was a significant difference in fuel injection volume at higher engine speeds.

Could it have been caused solely by the sealing ring?

Last edited on 16-06-2021, 20:17, edited 1 time in total.

chli1976 wrote:

It seems to be working again, but I'm not entirely sure yet.

I've also replaced injectors 5 and 6, so now they're all new.
The 5th injector was missing its sealing ring, which is why there was a significant difference in fuel injection volume at higher engine speeds.

Could it have been caused solely by the sealing ring?

Thank you for the feedback, I'm looking forward to it!

Here's another point regarding missing or loose seals on injectors or fuel nozzles: During the overhaul of nozzle holder assemblies, I've encountered numerous instances where customers failed to properly seal the nozzle holder assembly to the cylinder head. The effect was that the cold engine appeared to run normally, but as it warmed up, larger discrepancies in fuel injection amounts and running problems emerged.
A disassembled injector holder assembly from a customer showed discoloration on the new injector nozzle. It must have become very hot due to the passing exhaust gases and insufficient contact with the cylinder head. I suspect it was stuck because it was (open/closed).

The consequences of prolonged driving can be imagined, including engine damage.
Therefore: Always check for correct assembly and tightness!

I could imagine that similar effects occurred here.

Best regards, Rainer.