Intermittant non start

[C. Grimsley]

Evening everyone, i have a little issue with a 2001 Bmw x5 3.0 diesel, the car starts fine first thing in the morning and runs like a dream, if i get the engine up to operating temperature and then turn it off, leave it for ten minute the car will not restart (cranks over but wont fire), leave it to cool down and away it fires again.

I have had the car on the computer for a fault code diagnosis and no trouble codes are stored, i have looked at the live data whilst the engine is running but there is no option to check the crank shaft signal, this may be my first part to change and see what happens, hopefully the sensor is breaking down in side when its hot, this is what i am wanting it to be. A few garages are telling me its the injectors but i don't believe there theory or air getting in the system as if you leave it to cool it fires straight away.

Have any of you on here had a similar fault or have another idea of what it may be, its just i don't want to go spending on bits and pieces if they dont lead me to rectifying the fault.


Many thanks, Carl

Edited by C. Grimsley on Monday 21st September 18:46

[C. Grimsley]

No body have any clues?

Carl

Edited by C. Grimsley on Tuesday 22 September 07:40

[T-bagger]

Hi Carl,

Ok there are quite a few problems the X5 3.0d suffers with that could cause this problem. I've listed them in a prioritised order below, but what I would say is that a crankshaft sensor fault would almost certainly store a fault code in the DDE.

1. Injectors 'leaking off' excesively - This was once very common, a malfunction occurs within the injector that allows too much fuel to leak back to the return lines. This happens on initial pressure build up whilst cranking and drops the rail pressure sufficiently for the DDE to cut fuel supply as a safety measure. It is usually accompanied by a fault code equating to 'low fuel pressure on starting' or similar.

2. Faulty fuel pump relay - There is a green relay behind the glovebox that supplies power to both the intank lift pump and the in-line pump under the N/S sill. These quite commonly fail, and if I were you I'd replace it anyway as they're really cheap and bound be quite pitted on the contacts.

3. Faulty fuel lift or inline pumps - again these can fail, the one under the sill more commonly than the in-tank pump.

4. High pressure pump internal fault - Not usually the pump more the pressure control valve that built in, weren't available seperately last I heard. Difficult to diagnose and expensive to buy.

5. Faulty/corroded contacts on rail pressure sensor of rail volume control valve - have a close look at the electrical plugs on the fuel rail sensors (may have one of two dependant on build date).

If you need anymore help repost and i'll try to get back here later, best of luck.

[C. Grimsley]

Well have spent the best part of the day messing about with the car today and managed to find a few faults and at present the car runs fine and the fault hasnt re appeared.

Removed the crank sensor and it all checked out ok but i decided to replace it anyway, as i removed the plug one of the contacts inside where green, cleaned the contacts and put it back together, have to say it sounds easier than it was, in a lovely position on the lower part of the engine.

Thanks for all the help, i will repost back up in a few days and let you know the outcome.

Thanks again people, much appreciated.

Carl

[Remagel2507]

I came across this problem a while ago on a 525d (similar engine) engine wouldnt crank after being run up to Operating temp, we could only get it running by bumping it off. I think we changed the fuel temp sensor which helped slightly but the problem still persisted after changing a couple of the injectors though, the car started every time, fuel economy went up and so did performance.

Hope this helps

[Fox-]

Pre-supply fuel pump?