Audi A6 C6 2.0 CAGB common rail not starting

[martini667]

Hello. Having trouble to start my audi. Any help appreciated. It all started when i changed fuel filter and didn't prime the system. I know, my bad.. It sucked air into the system and was not starting. I managed to start it after a while, but then i noticed weird clicking noise when raising RPM's on idle. It came from the pump pressure regulator. I changed it to original part from other HPFP, and no starting since then. It cranks but wont fire. No metal flakes found inside HPFP. Tried bleeding system 5 times with connecting battery to auxiliary pump and in tank pump for 15-20 minutes, nothing. All air was out of fuel lines but still no start. Tried bleeding injector harness, still no start. Fuel pressure is low and not starting beacause of that. Could it be injectors stuck or i messed up HPFP? VCDS isn't showing any fault codes..

[philipharmes]

Your non-start & low fuel pressure started after you changed the fuel pressure regulator.

I would either put back the original FPR that seemed to work but clicked, or get a new one.

Make sure you bleed the system multiple times with both pumps before you try to start it.

[martini667]

I tried with old one, and new one, still the same and already bleed 5 times. I put a pieces of transparent hoses to intake from tank and return from pump to see, if theres any air left, but no. Fuel flow is good and no foam or anything. I think the best solution is to purchase fuel system pressure meter and diagnose how many bars will go into pump and how many bars pump presses out.

[Roverfan]

The fuel metering valve? If so they are matched to the hpfp on my 1.6 common rail. It also has an adaption process for ecu. See if that applies to your engine aswell.

[Crasher]

No swarf but it is easy to damage the pump if it runs dry.

[dan2485]

Have you put the fuel filter in the right way round?

if so, run the fuel transfer/pressure test in VCDS and check for leaks.

The car normally will start with 3 tests ran.

[martini667]

Fuel filter is fitted correctly, no leaks anywhere. 6 bars is coming from fuel filter to the HPFP, checked with pressure tester but low pressure in fuel rail according to VCDS. Not enough pressure is coming from HPFP. Strange is that after it run dry, it started and run with old metering valve so problem cant be seized HPFP. Looks like i messed things up when changing/opening the metering valve and new valve has to be recoded. Anyone knows how its done?

[Crasher]

If you know it ran dry and now you have low rail pressure, it is more than likely the pump galled internally and now cannot deliver full pressure, I have never known one seize.

[martini667]

Yes it did run dry, but engine did start afterwards. I think that problem may be still in fuel metering valve that is not working properly. Ive also read that its bad wiring can cause issues with it and my plug in socket is a bit damaged, so maybe replacing socket and checking damages for wiring can get me somwhere. If not, then yea, have to change HPFP.