Stalling - list of things to check?

[Sean H]

I'm having some stalling issues with my '89 535. No rhyme or reason to it; it has happened at freeway speeds and in a parking lot. Total number of occurrences is probably seven or eight, but they are becoming more frequent (three in the last two week) and longer in duration (ten seconds or so... previously it was just a "blip"). I feel it is a fueling issue, as the car doesn't totally lose power and all of the ignition components are relatively new (four years old or less).

My first plan of attack is to throw a fuel filter on it. I'll admit to laziness on this one as I haven't replaced it in nearly two years. If that doesn't resolve the problem, where should I turn next? Here are my thoughts:

Fuel pump relay (this is an original part as far as I know)
Fuel pressure regulator (ditto)
Fuel pump (same as above, but it is remarkably quiet for an E34 pump. The ones on my previous cars have all had an audible buzz even when in tip-top shape)
Crank position sensor. (This is only three years old, but I could have got a bum part)

Anything else I need to look to? I'd like avoid having the thing die on me on the connector only to have it not roar back to life. That kind of thing can totally ruin your morning.

[bubba966]

What brand of gas have you been running? Getting it from the same station? Have had that kind of stalling before when I had some water in the gas. A bottle of Iso-Heat cures it right up.

[Jr ///M5]

Main Relay, Fuel Pump Relay...but I would suspect the main relay first. I'm not for certain, but I believe you could swap the relay out of the 318 to give it a try.

JR

[ahlem]

check your fuel pressure

[Ross]

wasting your time with the filter. Look to an electrical fault, poor connections at the pump or a relay.

[Tiger]

Fusible link

[Sean H]

What brand of gas have you been running? Getting it from the same station? Have had that kind of stalling before when I had some water in the gas. A bottle of Iso-Heat cures it right up.

Citgo, BP, Chevron, QuikTrip, you name it... I get what's readily available when th elight goes on.

I'll check into the relays. No dice on swapping from the 318, though... that one's on a switch.

[3gunF1guy]

I had the same thing. When you are driving and it dies, does the tack drop to zero or does it stayat the rpm of the truning engine? If it drops to zero check the CPS. When it dies the computer shuts down the fuel pump and ignition. As soon as the computers gets CPS signals again it turns the fuel pump and ignition back on.

Scott

[Gene in NC]

3gunF1guy, my '89 525a tach drops as if going to zero, but pops right back up if the series of quick multiple stumble/stalls ends. What is CPS, and how does it fail intermittently?

[whiskychaser]

What is CPS, and how does it fail intermittently?

CPS= crank position sensor. Its a non-moving electric part that picks up the position of the crank and passes it to the ECU so it can make decisions about timing etc. Like any electrical part, it can fail at will. If it does fail, it also knocks out your fuel pump though this may not be relevant to your own thread.