1995 E34 540i

[nuts4bmw]

I hope someone here can help.

My car stalled and I was not able to start it again. Crank, crank crank, no start.

Pulled the fuel pump, bench tested it and it runs good.
Put it back in the car, but not into the tank. Plugged it in, and hooked up a test light directly to the pos and neg. terminals on the pump to check current flow. Turns out, the test light only lights up intermittently.
So I checked the fuel pump fuse, and pulled the fuel pump relay, Fuse is good, relay is also good. Try starting car again with test light still hooked up to the fuel pump terminals, and now shows a constant light while cranking motor. Screw everything back together, crank the engine, and it fires right up. Turned it off and restarted it over a period of a couple of hrs, and it fired up every time.

This morning, no start, again and again.......uhhhhrrrr..... frustrating.

I read in another thread fuel pump related, that is the crank positioning sensor is faulty, no current will be sent to the fuel pump.

So, how do I test the CPS if it is good or not? will a bad camshaft positioning sensor also cut off current to the fuel pump? How do I test one of those?

Electrical trouble shooting is my weakest when it comes to repairs. Any help will be GREATLY appreciated! Thank you in advance.

Art

[hakentt]

old fuel and old fuel pump

[marc79euro635]

CPS creates the pulse that triggers the spark and fuel injectors. Auto parts store should sell noid light that plugs into injector plug. When you crank the car the noid light should flicker indicating cps is working. You can also just pull plug and look for spark, as both are triggered by cps pulse. Fuel pump is activated by key, fuse, relay, obc, afm sensors. etc that can interupt power to the pump. good luck!