Cps?

[chefmike70]

I am trying to diagnose a problem with my 1987 325: It cranks like normal and fires after a second or so and then runs for about 5 minutes then dies. It will then crank and bark like it is trying to start. If I let it sit for a bout 30 minutes the pattern repeats itself. I have searched several post with similar problems and many solutions say to replace the CPS or crankshaft position switch. However, some say it is the two sensors bolted to the bell housing others say it is the little tube like sensor clipped to the front of the motor by the harmonic balancer. As I am on a tight budget (currently unemployed) I can't just buy all three. Which is the best to start with?

P.s. I have replaced the main relay, fuel filter, and pump relay and checked the fuel flow pressure as well as made sure the timing belt is not broken.

[blocke]

I believe that it was only Eta's that had the reference sensor in the bell housing.
I cant find a pic of it, but it would be the bottom left side of the engine, affixed with an allen bolt, pointing at the toothed crank pulley

[SpecM]

an '87 325 is an ETA with Motronic 1.0, so the the two sensors would be on the bellhousing

[M3PO]

This sounds similar to my problem but now mine won't start at all. I think the DME is getting a signal from the CPS because the fuel pump runs and the coil fires. So in my case at least, I don't think it's the CPS.

Your problem may not be either and since you are on a tight budget, I would test it before replacing it.

[rhE-30]

Does any one have a quick run down on how to test the Cps? or which page is it on in the bentley?

[rhE-30]

Bump

[jlevie]

My first suspicion in a case like this would be the fuel system. Tee a gauge into the supply line to rail and see what the pressure is and what it does as the engine dies.

My second thoughts would be of an intake leak. One large enough to cause problems as the engine goes into closed loop mode, but not big enough to prevent starting when cold.