Cut off while driving

[BMWerke]

The other night my E30 wouldnt start at all so i left the car over night and it started up perfect the next morning. Usually once every couple of days it wouldnt start on the first try but it would always start on the second try. Now it does this at least 3 times a day, it will just crank the first time then it will start but at like 400rpm for a second or two then jump to around 700 where its supposed to be and then it runs fine. well today it cut off while i was driving completely and then i got power about 5 seconds later. Then as i was goning down my street it cut off again and wont start at all. Relay, DME, Fuel pump?

[smcdermott326]

yeah start with the main and fuel pump relays. Cheap insurance either way. You can smack 'em with a screw driver handle while the engine is idling to see if you can recreate a stumble or cutoff.

[CorvallisBMW]

My first thought is crank position sensor or spark impulse sensor. Check those connections next to your diagnostic port.

[BMWerke]

i have an 1986 325e donor car, is the cps the same in my '90 325is cause if it is i could swap it and see if that is the problem

[blocke]

I know this sounds stupid, but are your grounds clean and solid? Like the battery ground, and the engine block ground? I know mine got a little corroded, and I was experiencing slightly longer cranking times. Cleaned them up, and the car cranks right up.
Something to check out while your at it.

[CorvallisBMW]

i have an 1986 325e donor car, is the cps the same in my '90 325is cause if it is i could swap it and see if that is the problem

No, different parts

[Matt-B]

happened to me. fuel pump or cps

[CorvallisBMW]

possibly plugged fuel filter too

[BMWerke]

let me check the grounds