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Matt, Mechanical Engineer
Category: Audi
Satisfied Customers: 22769
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have an Audi A6 V6 Quattro KD55 EKC (62,000 miles), over

Customer Question

I have an Audi A6 V6 Quattro KD55 EKC (62,000 miles), over the past 2 - 3 months its had problems starting, it got worse and worse, from only starting on 2 - 3 turns and white smoke when it eventually did start to now when it doesn't start at all. When I got an Audi mechanic out to my house he tested it and got an immobilser type error up on his tester (blocked message), but its the same key I've always used and I get no errors on the display either. I've had the EDC on the top of the diesel pump tested by disconnecting it and sending it to a company that does this sort of testing and all was found OK with it. Could it now be a diesel pump (mechanical) problem? The company that I sent the EDC too said its highly unlikely, any suggestions would be greatly appreciated.
Submitted: 4 years ago.
Category: Audi
Expert:  Matt replied 4 years ago.

from what you've said its sounding more like an electrical issue

so its worth checking that the electric pump that feeds the main fuel pump is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If the connections to this are corroded or damaged then the pump could stop at any time. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse, ideally measure the voltage at the pump and check its getting 12V

Also if its not injecting at all then check the connections to the crankshaft sensor, unplug it and check for corroded contacts and broken wiring, and consider fitting a new sensor - do the same for the cam position sensor
If the EGR valve is stuck open then this too can effect starting so try disconnecting it to see if this helps or changes anything

Could also be an injector leaking fuel back through the overspill pipe, so not getting enough fuel pressure to tell ECU to fire the injectors, this is trickier to find and you’ll need the garage to do a ‘run back’ test to identify which one is the issue
Lastly it’s also worth considering fitting a new fuel filter as if only slightly blocked this can lower fuel supply pressure and choke the main pump, the pump will be more sensitive to this when its cold as diesel thickens considerably with low temperatures.