Q Banks

2011 Audi A8L 4.2L

On cold start, car starts up find
After driving and then restarting after 20 minute, car struggles to turn over and only actually does when I press on the accelerator (gas pedal)

I saw in another thread that someone had the same issue with their D4 S8 and eventually found the solution being the high pressure fuel pump (1 of them ) not working correctly (so they had to replace it and it rectified the issue.

My question is - does the Audi A8L D4 have 2 fuel tanks and if so does that mean it requires 2 High pressure fuel pumps? { 1 installed directly into each gas tank???}

Anyone please let me know...Thanks

collantes_C6

​Were you able to solve this start issue?

MP4.2+6.0

For posterity in this thread, the original question is mixing up the fuel pumps. On a D4 V8 there is one low pressure pump in the fuel tank. Its job is only to move fuel forward. They got rid of the old two tank pump design from the D3 even though it is still a saddle tank. There are two high pressure fuel pumps, one for each side of the motor.

Big picture, yes warm no start is often a sign of a fuel side issue. Besides the pumping function, it can be a check valve that isn't maintaining residual pressure when off. You would need to look at the parts diagrams to see if those are separate replaceable parts or integrated into the fuel pumps.

igli

were you able to fix it , what did you ended up replacing?

Josh Butcher

The warm start issue is a common problem of leaking high pressure fuel pump (on top of engine) leaking into engine oil. Lifting oil cap and smelling fuel is easy indicator. Using vcds or similar to monitor fuel pressure at shutdown will also show loss of pressure indicating leak. There was a batch of auto tech plungers that were faulty and leaked.