All Things Mk5 > Mk5 General Area
Fuel pressure problems
Uncleben:
Yes, that's me!
I don't have access to vagcom, but do have access to an audatex diagnostic system which I used today to measure some values, I didn't really know what I was doing so will just post the values I recorded and hopefully you can make sense of them!
Measuring block 103, fuel pressure(low) 4-5bar at idle, didn't measure this when revved to see if it drops, doh!
Measuring block 106, (duty cycle?) 45% at idle, rising to 90% when revved.
Measuring block 140, fuel rail pressure, was 50bar idle rising to 90bar when revved to 2500rpm, then dropped to about 2 as it died
The specified and actual rail pressures are within 2 bar all the way from 50 to 90 when it dies.
The only code that comes back each time it dies is P310c low fuel pressure regulation ;fuel pressure breaks down sporadically, from what I've read, that does not relate to hpfp?
Cheers for your help
pudding:
106 is fuel rail pressure and the % duty is the engine ECU's PWM command on the fuel pump controller, which is under the rear seat. 90% is massive, it shouldn't be anywhere near that high at only 2500rpm!
When was the fuel filter last changed? I suspect that is either completely clogged if it's never been changed, or the in-tank pump is dying, hence why the high pressure pump can't cope either.
Uncleben:
Fuel filter has been done (6.6bar), along with a known working lift pump from a mates car (to rule out a faulty secondhand pump I'd fitted being faulty)
According to Ross-tech, P310c likely causes are faulty lift pump (g6) clogged filter or empty fuel reservoir.
I have recently ran the fuel tank to 0 miles to empty, but this issue was already present by then.
pudding:
Blue and black fuel lines put back in their correct orientation on the filter? Some folk have made that mistake. Although saying that, I can't remember if the engine doesn't run at all, or if just enough fuel gets through for idle and not much else.
Fuel pump controller under the seat getting very hot?
It might be time to book it in for visual inspection because a car with 2 fuel pumps, a pump controller and 3 fuel pressure sensors isn't the easiest thing to diagnose on a forum.
Uncleben:
The fuel filter was the last thing i replaced so can rule the pipes out.
Haven't checked the controller getting hot, but did replace it for a known working one which made no difference.
I appreciate its not easy without seeing the car, I just cant find any mobile mechanics willing to delve into complex diagnostics!
I will measure fuel pressure at the lpfp again, but see if it drops when revved like it does at the hpfp, if so then that must be a fault with the low pressure side, as a faulty hpfp wouldn't affect the low pressure?
Really appreciate your help :happy2:
Edit: so i've just measured fuel pressure at the LPFP, was 4.8 bar at idle, rising to 6 when driven, dropping to below 2 as the engine died.
So a drop in the low pressure side would cause a drop in the high pressure side but not vice versa? i.e; a faulty hpfp wouldnt cause the pressure to drop at the lpfp, but a faulty lpfp would cause the pressure to drop at the hpfp?
so it seems the problem is still with the low pressure side, as the P310C code is telling me!
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version