Starting issue with 2002 740i

[david broughton]

I have a really frustrating problem. When I try and crank the car it turns over but does not start. It makes the noise as if it is going to start but does not. Most times if I switch the key off and then turn it back on it will start. I have replaced the cam shaft sensor, the battery, fuel filter, and fuel pump with no success.

[brettski]

Welcome to the Werkz.

Once it starts does it run ok?
Does it only do this when cold, or left off for more than an hour or two?
Are there any other symptoms that youve noticed?

[david broughton]

Yes it runs fine once started, but from time to time it will just cut off while driving. If that does occur though it cranks right back up with no problem. Yes it only really occurs when the car is cold or left for a few hours. You hit it right on the head Brettski, and correction the car is a 2001 model

[brettski]

The stalling once running sort of kills of my idea that it could be a leaking fuel rail pressure regulator issue, and I think you have the regulator built into the fuel filter itself. I am not sure if there is another one on a return line from the end of the injector rail. Might be worth a look though. The other suspect if the CPS, but you've already change that.
When its stalled after running, was it under load, or just idling?

[david broughton]

Thanks Brettski i am going to look into the return line theory, and when it stalls it i can be at a light idle fine and then when i press the gas the stall occurs

[brettski]

Try disconnecting the Air Mass Sensor to see if that impacts on the problem, also check the intake manifold and ducting for vacuum leaks. That can mess with the air fule mix ratio.