[willisodhiambo]

I am trying to resolve occassional hard start in an E53 N57 engine. History given to me is all 6 injectors already replaced with refurbished units. I started with the fuel system and this is what I see

1. Rail pressure ignition off - 3-4.7 bar
2. On start pressure quickly rises to 387bar.
3. On ignition off Pressure quickly drops to 80bar then gradually to 4 bar within half a minute to 1 minute

I am thinking it needs to maintain rail pressure for longer? This is my experience with newer engines, not sure if the case with the older engines. On one occasion pressure was about 300bar but it still took a few moments to fire. 

I suspected injector leak even if all were replaced but the return flow seems to be consistent across the cylinders. I notice a little black smoke at the exhaust as if too much diesel is being injected but I want to solve the occasional hard start first.

Only other culprit i might suspect to be causing it would be the camshaft sensor. There is no test for cam position on this test and because it is occasional it is difficult to catch.

Any ideas?

[tonemoz]

E53 M57? If so, fuel pump relay is common to burn out on these.

[willisodhiambo]

E53 M57? If so, fuel pump relay is common to burn out on these.

Yes it is. Thanks for the lead. I'll have a look at that too.

[willisodhiambo]

E53 M57? If so, fuel pump relay is common to burn out on these.

Unbelievable some of these problems!! I am sure I checked fuel pressure and once caught it when it had a hard start. Fuel pressure was reading just fine!!

All the same went with your advice and swapped the relay. Problem solved, one week now!! Simply incredible. Thanks!!