m_smith is correct. The fuel pump will not start pumping until the ECU sees that the engine is turning. It gets this information from two places, one is the crankshaft speed sensor and the second is the camshaft position sensor. I think it needs to see both of these before it energizes the fuel pump so you may not see any power at the pump unless you are cranking the engine. If you see power when cranking then you need to check to see if you have fuel pressure. If you have power at the pump and the starting has been intermittent and you have over 120k miles on the car there is a pretty good chance the fuel pump has died.

I have never done a pump on a C5 but I have done them on C4 and B4 body styles. The job is not that bad if there is not much fuel in the tank.

 

Good Day
I have an 2001 Audi A6 4.2 V8
The car was standing in my garage for 3 years but never ever started it
One day I tried starting it but to no avail
I traced the fault to the fuel pump and then changed the fuel pump.
IT started first time and the motor ran smoothly
I took it for a drive and it went beautifully
I came back home and switched it off and restarted it 3 times, then the fourth time it only cranked over and would not start.
What now I thought, checked the fuel pump and it was burn't.and not working.
I have since changed the fuel pump now three times with the same problem.
Can anybody give me advice on what to look for
It seems to me that it is getting a voltage surch to the pump causing the pump to burn out.
email martin@vmcranes.co.za
Thank You
Martin