Occassional long cranks - what could it be?

[entscheidend 0]

ok - This car is a 2000 540i M Sport.

It started with long cranks before it would fire up (this only happens 25% of the time whether in the morning or parked for 30 minutes and come back). Once going she goes like a rocket with no hesitation at all.

We have changed over the crank sensor and put cps's from a good 740i and see if that made a difference. nothing.

Checked for spark, fuel pressure, relay all good.

Did a smoke test on it and it appears there is a vacuum leak by the PCV (rear of the manifold)

No faults picked up either except for a O2 sensor which could be the vacuum leak

This couldnt be the reason for the long cranking can it???

Could it be a ignition switch??

[*Glenn* 854]

Scan it first. However, if you have an air leak that needs to be fixed first... will create heaps of problems. The ventilator valves and manifold gaskets give problems and occasionaly the plenum chambers need replacing due to distortion. If this fault is confirmed, you must do that first. I'm sure Ross would have suggested that.

[entscheidend 0]

Scan it first. However, if you have an air leak that needs to be fixed first... will create heaps of problems. The ventilator valves and manifold gaskets give problems and occasionaly the plenum chambers need replacing due to distortion. If this fault is confirmed, you must do that first. I'm sure Ross would have suggested that.

We have had it scanned - not picking up anything. I have had people tell me it could be the ignition switch as E53's with the same motor etc have had the same issue.

So you think I should fix the vacuum leak and see what happens before I move to the ignition / timing side of things?

[*Glenn* 854]

We have had it scanned - not picking up anything. I have had people tell me it could be the ignition switch as E53's with the same motor etc have had the same issue.

So you think I should fix the vacuum leak and see what happens before I move to the ignition / timing side of things?

If its faulty...yes. Otherwise you arent going to know what you are actually dealing with. You already know it has an air leak...you must do this first and hopfully nothing else will show up. The air leak will be affecting all readings from the air mass sensor, including start up. Out of scale readings from the air mass sensor should throw up oxygen sensor out of scale fault codes. Power to the DME relay on start up can be also checked quite easily as well.

Edited February 9, 2009 by *Glenn*

[entscheidend 0]

If its faulty...yes. Otherwise you arent going to know what you are actually dealing with. You already know it has an air leak...you must do this first and hopfully nothing else will show up. The air leak will be affecting all readings from the air mass sensor, including start up. Out of scale readings from the air mass sensor should throw up oxygen sensor out of scale fault codes. Power to the DME relay on start up can be also checked quite easily as well.

Thanks Glenn - one more question, is there a way to take the rear cover off (or PCV) the back of the intake manifold without the taking the intake manifold off?

[*Glenn* 854]

Thanks Glenn - one more question, is there a way to take the rear cover off (or PCV) the back of the intake manifold without the taking the intake manifold off?

Yes ...quite easy with the right tools

[entscheidend 0]

Yes ...quite easy with the right tools

mmm .. I need a smaller wrench or a actual T27 right angle driver. I cant get 3 of the bolts on the back

[*Glenn* 854]

mmm .. I need a smaller wrench or a actual T27 right angle driver. I cant get 3 of the bolts on the back

T27 with a 10mm spanner on them work. My set you can use sockets or spanners on them. Make sure they are good quality and also make sure they have gone into the torx properly...or it will be manifold off and passibily alot more $$

Also be careful you take care with the pipe fitting going ito it from the timing cover on the L/H bank and dont let anything fall into the plenum chamber when you have the valve out