Root-causing starter issue

[ktteoh]

typically, the m50 engine will crank & start when i turn the key.

only today, i need to give the accelerator a dap before the engine cranks to life - otherwise it is cranking but it's like there is no ignition.

how do i rule these out:
1. crank position sensor
2. fuel pressure regulator
3. fuel filter (blockage) - the one behind near fuel tank

[Dave M]

Having to give the throttle a tap doesn't lead me to believe any of these items would be at fault. If anything, maybe the ICV (idla control valve) is sticking or something else affecting the o2 supply or mixture is at fault.

Anyhow,

1) CPS is an easy test with a potentiometer (electrical tester-cheap at any auto parts/electrical supplier) and the Bentley manual. If you need the resistance values from the Bentley, one of could provide them for a small fee. Or, they may be hanging around in cyberspace, available via the search bfunction

2) Probably want to invest in a fuel pressure tester (mine was ~$30). Then you can test running pressure and how quickly it drops after the pump is turned off.

3) Don't have much experience with bimers and fuel pumps, but its a cheap part and might be wise just to replace it regardless. Ask yoiurself when you did it last. If the answer is "I don't know", then just do it. I have one in the garage as I provided the same answer when i asked myself the question.

Hope this serves as a starting point,

Dave

[Blitzkrieg Bob]

My first step would be to clean the IVC valve and throttlebody.