Where to start looking for a stalling issue.

[rockin1978TA]

My 89 535i, died on my way to work this morning. I was at a stop light it it just stopped running. No bad idle or shuttering. The weather was very high humidity this morning, with rain on and off. I turned all switches off, then tried to start it again, several times. No luck. Got it pushed into a parking lot, got a ride back home and grabbed my sons volvo. On my way back out of town, I decided to stop and see if she would start, and she fired right up. I decided to just leave it there till I got off. After work I got a tow home, then got it started it right up, drove her around she seemed fine. Where should I start looking, as this is a real pain, when people behind you start honking.

[ahlem]

Fuel pressure due to the start of a failing fuel pump or more easily checked, a relay getting corroded. Fairly easy to clean and inspect and free to check relays.

[rockin1978TA]

Well I've been driving it for over a week now, and no problems till this morning. I was at a stop light, and I noticed the RMS dropped , then it caught it self. I do have an intake gasket on #1, that needs to be replaced, but has been sealed with copper gasket sealer, and does not sound like it's leaking. Only think I know that I did do, was when I changed out the radiator, I cleaned a bunch of gunk from the crank sensor. This problem seemed to have stared after I changed out the radiato. I know the fuel pump was changed out before I bought the car about 20,000 miles ago. Maybe this is the reason the last owner changed the pump? I might try getting a relay, and changing it out, to see what happens. If it did this all the time it might be easier to diagnose it, but it is very random right now. I can't get it to repeat in the driveway.

[Tiger]

CPS! Crank Position Sensor.

[rockin1978TA]

I'm starting to think the CPS also. Thats the only thing running wise I messed with when changing out the radiator. I cleaned it, maybe I should of left all the gunk on it. Maybe before it wasn't working. Also, I notice the cable for the CPS plugs in at the top of the engine near the thremostat/fuel rail. There is another connector just like it next to it. This other connector and cable, what does it go to? Mine goes down between the intake, then, it is cut, just hanging there.

[rockin1978TA]

I got under her, checked the CPS, it was a little loose, so I tightened it up. I noticed the wire for the CPS, is routed down through the intake, goes over behind the thermostat, then runs between the lower radiator hose, and timing cover, and ends up near the A/C compressor. Is this correct? When I changed the radiator, I changed the lower hose. If I move the wire on the other side of the hose it will come in contact with the waterpump pully. I was able to clean all the gunk off the CPS, tested the relays at oreillys, and cleaned the contacts. Also, I changed the hose from the fuel pressure regulator to the fuel rail. This hose crumbled when trying to remove it. Then I sprayed carb cleaner in the intake, after removing the air filter. She seems to be running good now, we'll wait and see...

[rockin1978TA]

Checked the resistance on the CPS, it is 640 ohms. Bentley says it should be 540 +or-10%, if not replace. So, it looks like I'll try replacing the CPS.

[genphreak]

A slightly loose CPS will cause that. Sounds like you best keep a spare even if it is now sorted out though, Mr Bently is a fairly reliable sage.

The other connector is the oil level switch