'90 535ia won't start

[Dash01]

Car ran perfectly til this afternoon, until I turned it off briefly. Then, it would not start, or stuttered at ~500 rpm and would die if the throttle pedal is pushed.

All gauges are normal.

Did stomp test, but it shows no diagnostic fault codes.

Removed and reset relays, and after that the car would not even stutter, or start.

Diagnosis?

[jjw]

There is a very good chance the fuel pump just let go. Check fuel pressure and spark. How many miles is the car and if it is the original pump. Both of mine went south about 80kmiles

[Dash01]

Car has 260K miles and AFAIK, it's the original pump. At the moment, I'm poking around with the relay, but don't have the proper 16 amp jumper to try it.

When turning the key, should I hear the fuel pump turning? If so, what should it sound like?

[romus]

like a buzzing noise... 1 or 2 seconds...

[ArtemLepilov]

like a buzzing noise... 1 or 2 seconds...

Umm... this might be a stupid question but was there enough gas in the car? I remember mine dying like that when i just needed to fuel up.

-Artem

[winfred]

just a piece of wire will do fine for a few seconds of testing, use small gauge wire if you are worried that way you can feel it get hot if it's drawing a ton, usually they don't draw much when they crap out, you'd pretty much need to be by the tank to hear it, it's a low buzz or hiss


Car has 260K miles and AFAIK, it's the original pump. At the moment, I'm poking around with the relay, but don't have the proper 16 amp jumper to try it.

When turning the key, should I hear the fuel pump turning? If so, what should it sound like?

[Kalevera]

Dash, I wouldn't even waste time fooling with the relay until the basic question has been answered: fuel or spark?

Very few things to look at on the M30. No spark? Troubleshoot ignition (cap/rotor/coil, CPS, main relay). No fuel (pull the line at the rail -- lots of pressure and fuel? not likely a fuel problem)? Troubleshoot fuel delivery...Jump the relay, check the lines, fuel filter, and pump. The other necessary element, Air, won't keep the engine from not turning over.

As with anything, it can get more complex, but that general process will solve 95% of the no-start faults with these motors.

Good luck!

best, whit

[Dash01]

So, if the fuel pump crapped out, the car of course would not start, but the fault codes would not register, either, right?

And, the tank is full. I suppose the brief stumbling start at ~500rpm could be due to residual line pressure being enough til it bleeds off. Does this make sense?

Would a paper clip be OK for a jumper cable to test the fuel pump?

Finally, one of the 635csi guys replaced his in-tank fuel pump with one from NAPA, for ~$70, as I recall. Works fine. OEM fuel pumps for E34 535i cars run about 4 times as much. So, has anybody tried substitute pumps in our E34 535i cars?

[winfred]

the 6 series has a small secondary intank pump that can be replaced by just about anything, the e34 has it's primary pump in the tank, i don't recomend aftermarket as they usually suck

[romus]

yeh i had my 3 series die on me after i worked on the fuel line and eventually took out all fuel in process of testing. When i was ready to drive, the more id press on accellerator, the less breath it'd have.

But i also had similar symptoms with clogged fuel filter and pump (on an E30)...havent had such probs on e34.

[Dash01]

Did jumper test on fuel pump relay using fat paperclip. No start or sputter, and no smell whatever of fuel vapors at the tailpipe. No audible sound from trunk area that might be fuel pump, but then I don't recall hearing it previously before start or when the car was running.

Did stomp test, and no fault codes are shown.

DEFINITELY has spark.

So far, is this all consistent with a faulty fuel pump?

And, in the '90 535ia, can just the pump motor be replaced, or is it necessary to replace the whole in-tank assembly?