My 2000 Audi A6 2.8 30v APR engine will crank fine, but is just not starting. The main issue is the 'fuel pump' does NOT prime / turn on when you turn on the ignition key. The car has been running absolutely fine previously, but this happened after I replaced all the vacuum lines (they were seriously brittle / broken) don't think that's related though?
Anyway things I've done thus far :
1. Replaced Fuel Pump Relay (although original tested fine)
2. Replaced Fuel Pump fuse # 28 (although tested fine)
3. Tested 12v power at the relay panel - fine
4. Measured voltage at fuel pump connector (across pins 1 & 4) - 12v ok
5. Bypassed Fuel Pump Relay to provide 12v directly to Fuel Pump (Fuel Pump activates just fine!)
6. VagCom engine output tests carried out - can hear fuel pump, fuel injectors spray, solenoids etc.. - all seem ok.
7. Replaced Crankshaft Sensor (although original tested fine with Vagcom) - Get ~ 160/200 Engine RPM when cranking engine
8. Removed Throttle Body, cleaned, re-installed and did adaptation with Vag-com.
9. Added 10L of fuel as car was low on fuel (always put in high Ron fuel - Momentum 99)
10. Tested all other fuses in side panel - all ok.
11. Tried cold-booting the car. Remove both battery cables from the battery, shorted the battery cables together (away from the battery) for about 20 secs
12. NO vag-com engine error codes displayed at all.
For some bizarre reason the fuel pump relay is just NOT activating the fuel pump when turning on the ignition key.
I've read when some of these cars are started the ECU/ECM looks for a signal from the crankshaft sensor. If it missing it will not activate the fuel pump relay - preventing it from pumping fuel in case of an accident where a fuel line gets ruptured - but I've already replaced the Crankshaft sensor, and tested it with Vag-Com to no avail.
Next, I thought it might be the ECU relay, but could not locate it in the ECU Box Plenum Chamber under the windscreen, in fact nothing there other than the ECU itself - then phoned Audi who confirmed my particular engine does not have one!
Things it could be? -
1. Ignition switch - although all electrics work fine, windows etc
2. Starter relay - although can't locate it
2. Air lock in fuel delivery - accidently opened a fuel line when removing the throttle body, spilt a little fuel, but put the hose back on..
3. Should I try spraying some 'easy start' ....?
3. Fuel pressure regulator
But I don't think any of the above would prevent the fuel pump relay from turning on when the ignition key is turned on? There is NO sound at all emanating from the fuel pump when the ignition is turned on...
Any advice much appreciated!