Audi Repair Questions? Ask a Mechanic for Answers ASAP
You can pull the fuel line off the rail, and direct it into a glass jar, and see if you get flow while cranking. I understand what you are saying about sudden failure, it seems odd with a fuel pump, especially a new one. So if you get no flow, I would check power at the fuel pump connector while cranking, if you have no power you have an issue with the fuel pump relay or something.
When it starts on starting fluid, it just runs until the fluid spray is gone, correct? So you know you have spark, so your crank sensor is not the issue.
But it won't stay running with the key in the run position, correct? Just making sure that it isn't the ignition switch, cutting off the pump in the start position, but allowing it to run in the run position. Typically when this happens you get a "stumble" like it is going to start, just as you let off the key.
Yes, I am just clarifying. You do need to have about 30psi of fuel pressure on these. When you hear the pump cycle, you are hearing the actual pump in the rear, not just the relay under the dash, correct?
Have you checked the fuses for the fuel pump (s17, 15a) and for the injectors (s72, 12a) It could be that you are getting pressure to the rail, but the injectors are not opening.
Yes, the injectors are fed constant power through fuse 72- and then grounded in turn by the ECM in order for them to open. You would need to check pressure with a gauge on the fuel line- but like I said, you can just look for the injectors, follow the fuel line back, and find a place to disconnect it and route it into a glass jar or bottle and make sure it is pumping when you are cranking.
Take a look at page 29-30 of this fuse listing- the "electronic box" behind the center dash holds the fuse s72.
Sorry, should have said pages 30- 31, not 29-30 One more page would have shown you where it was. If you look at page 30, it shows the ECM and circuit breakers, the one that is listed in the wiring diagrams as S72 is the circuit breaker in position 5 there.
And yes, it is inside the dash area. This is what mechanics do all day, dig in deep!