ludviks@online.no

I have an audi A8L 2008 3.0 diesel. It starts almost without any trouble when its cold, but if I run it until its hot, it won't start again. I changed the starter relay and the fuel temperature sensor, but it still wont help. I got a fault code for the pressure sensor and the pressure relieve valve. But i wonder if it could be the high pressure pump. If I stops it when its warm, it will start again without trouble within a minute. If I wait to or tree minutes it wont start again until its cold. Then it sometimes seems to start on two or tree cylinders before it starts up like it should.
Need help!!

I`ve changed both crankshaft position sensors, the fuel temperature sensor, the fuel pressure regulator, the high pressure pump but the problem is still the same. The fuel is running to the pressure pump so it should not be the pump in the tank. Someone said it could be the fuel injector, could it be? Sometimes when it starts the engine makes some knocking noise before it runs smoothly. Still, when it is warm it will not start again. It cranks but would´t start.
​​​​​​​Help!!

Jack88

A fuel pump is a good possibility, I really don't know where else to point you, but you should do a search on the forum and see how everyone else handled this. There are ways to diagnose it.

Mister Bally

Classic symptoms of a bad crankshaft position sensor (Engine RPM sensor). I assume the engine cranks but does not run, correct?

While I am not familiar with the D3 diesel engine option, if the engine has the same type of crankshaft position sensor, I'd consider replacing it.

That said, your fault codes point to a fuel system problem. I'd use the guided Fault-finding steps in the service manual. Buy it if you don't have it or an AllData subscription.