A7 CRTD - P008700 & P008800 Fuel pressure issues

J

Jellywopter

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Hi folks,

My A7 has been plagued by a load of very strange fuel pressure issues:

P008700
P008800

Leading to it having the timing chain done, fuel pressure regulator swap out, injectors (and seals) and basically everything on the fuel rail but the HPFP.

The garage have tried swapping out the leak-off pipe (as per the Darkside videos) but still no joy.

Anybody else had any issues similar? Are there sensors in the HPFP that a prone to damage that would flag these codes up?

67-plate 3.0 TDI Single turbo CRTD engine

TIA
 
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When was the last time the fuel filter was replaced?

What systems are you actually experiencing when driving? Is it going into limp mode?
 
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2 errors the opposite of eachother, either a sensor or a pump as in lift or hpfp would be my things to check.

Assuming checked got blockages too, fuel flowing normally to injectors?
 
Hi folks,

Thanks for the replies.

@The Jargen - Fuel filter was the first thing I replaced, only around 200 miles ago. No difference. I'm getting the glow plug light on, then EML after two or three occurences of the glow plug light. This is under load too, the folks at the garage are seeing it at about 3k RPM.

@NHN - Yep, that's what's stumping the garage! Weird errors at both ends of the "pressure scale". Injectors have been tested too, all seem to be working ok. I believe there is one other sensor that the garage are checking, then they're going to start swapping out lift pumps / HPFP. There is no glitter in the filters so they're reluctant to swap them out until they're absolutely sure it's that.
 
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Update - the car has been moved to Manchester Audi for diag and repair. It has stumped everyone else who has touched it!
 
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Update - Audi have found that the car has been mapped, it's come up with a TD1 flag so is now not covered under warranty....the joys!

Looking more and more likely to be the HPFP, especially after the research I've been doing (admittedly I'm not an Audi Master Tech!).
 
Apparently not, no glitter in the filters. Question for the floor - are the Fuel Metering Valve and the Fuel Pressure Regulator the same thing on our cars? I've seen things written that the Fuel Metering Valve is prone to clogging and can only be replaced as part of the whole HPFP assembly, is that correct?
 
No two different components. The metering valve can be changed without changing the HPFP and is found on the HPFP itself. As the name implies it meters the fuel from pump, basically flow control. The Fuel Pressure Regulator is found on one of the fuel rails and maintains pressure to the injectors.
 
Gotcha thanks! So could this potentially be sending things haywire? If the screen on the metering valve is gunked up?
 
It really shouldn't be gunked up in all fairness. Only if the pump is breaking down will you see glitter in there.
 
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Interestingly, the garage have given me the car back to use whilst waiting for the part to arrive - I'm driving around and only getting the P008800 code (with the flashing coild light)...a mis-diag perhaps?
 
Update - all fixed! The new ECU has solved the issue - £7.5k later...

The issue was apparently a bad eco map that was causing issues with the AdBlue system, and therefore misfuelling in a strange way.

Manchester Audi managed to sort it within a couple of days once the new ECU arrived.

I'm a very very happy boy to be back in the '7 after what's been a very long and stressful year!
 
Why would the just flash it back to the default map? And even if they wouldn't do it another reputable tuner could?
 
That was my question to them exactly, but that wasn't an option apparently...

Not thrilled about having to shell out so much money, but very happy to have it back.
 
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