starting issues/running issue

[Reavely]

hi guys,

so my Q7 is is the 2010 3.0 litre v6, I bought it a couple of years ago and haven't had any problems with it until last week when it broke down on me when I was waiting in traffic, the code reader said low rail pressure, this could be anything to I started to diagnose, no issues it seems from the fuel tank and the leek off from injectors all match up, however this is the strange bit, I had the car recovered and taken home, didn't touch it for two days, but when I did I got in it and it started straight away and run perfectly until cutting out 10mins later, try starting it up again and nothing happens she just turns over and over, unless you put your foot on the throttle and she starts but dies when the revs return to normal idle! this would all indicate a fuel issues however wait half an hour and she fires up straight away and runs perfectly for 10 mins then dies and the whole procedure repeats!

so does anyone have any idea where to start with this?

thank you

R 

[Steve Q]

Could the car not be getting enough air into the engine, this meaning an issue with the MAF sensor? 

Or it could be an injector fault. I have heard of cases on this engine of two injectors shorting out thus the ECU shuts down the car. 

I also found this via googling: 

Summary TPI Account №: 2014766/5
3.0 liter / 2.7 liter TDI: sporadic malfunctions of the engine permits the publication date: 10-08-2009

Problem Description Client / Conclusion station

The warning lamp lights up the engine and / or the engine stalls.

Errors in the engine control unit: P0200 (nozzle - an electrical fault in the circuit) or

P1195 (control valve fuel pressure open / short circuit to ground) or

P1281 (fuel metering valve, a short to ground) or

P1572 (valve left engine mounting -N144, short to ground) or

P2009 (regulating valve intake manifold, a short to ground) or ...


May be affected by all nodes connected to the corresponding branch harness: the fuel temperature sensor, glow plug control valve fuel pressure sensor, camshaft sensor, coolant temperature sensor, exhaust gas temperature, intake manifold flap, electro-pneumatic pressure transducer, high-pressure pump, terminal 50 starter switch reversing lamps, oil pressure sensor, the left support of the engine, generator, etc. kl.61

Technical Background

1. The engine wiring harness rubs against the arm of the fuel filter, causing electrical interference.

2. Engine harness rubs against the bracket 'bracket lifting motor', causing electrical interference.

The figure shows a bracket on the left side under the coolant expansion tank - the right-hand side may also be affected -> same metal bracket.


Fits in with what you say, when you toe it the engine will be moving more which may be causing a short between an injector harness wire and the chassis. Check the run of the harness from the engine back to the ECU. 

hope I've helped. 

cheers

Steve

[Bigdave1230]

I’d check/replace the fuel filter for signs of anything nasty in there that could be restricting fuel flow but it sounds like a fuel pressure/pump issue. My mate had a problem with a regulator that created a low fuel pressure fault code but I think his symptoms were a little different to what your experiencing. Unfortunately he’s moved to Australia so I can’t just ask him. If you have vcds you should be able to do some checks in the adaptation. I’ll email him and see if he replies. Good luck

[Reavely]

Thanks guys, a lot to look at I’ll keep you all posted 

[Steve Q]

8 hours ago, Reavely said:

Thanks guys, a lot to look at I’ll keep you all posted 

You're welcome, please keep us posted 🙂

Cheers

Steve