Hard starting - 535i

[Sean H]

The car has developed an intermittent hard start problem that I can't put my finger on. The battery seems OK; no hesitation or a slow starter or anything like that. The problem seems to be random; car can be warm or cold, recently driven or having sat for 12 or more hours. Another oddity: twice after it has taken an extended time to get the thing started, the "Anti-Lock" light has come on. Finally, it doesn't affect drivability at all. Once the car starts that's the end of the drama.
Any ideas?
Sean H
'89 535i
'84 318i

[Interceptor]

The car has developed an intermittent hard start problem that I can't put my finger on. The battery seems OK; no hesitation or a slow starter or anything like that. The problem seems to be random; car can be warm or cold, recently driven or having sat for 12 or more hours. Another oddity: twice after it has taken an extended time to get the thing started, the "Anti-Lock" light has come on. Finally, it doesn't affect drivability at all. Once the car starts that's the end of the drama.
Any ideas?

There is one thing you can do and it will probably solve your problem - clean all the electrical contacts with Stabilant. All the connectors (coolant temp, engine temp, CPS...) have a tendency to oxidate over time.

[NickM535]

Hi guys,

Pushing this back to the top of the list to see if we can get some answers as i have the exact same problem but cannot pinpoint it...

thanks for the help

[Kalevera]

Seems like a fuel pressure issue to me. All of the standard fare stuff applies, but it may just be the sending unit, in which case the check valve retrofit will take care of it. Leaky injectors (BTDT), clogging fuel filter (unlikely, but still...), fuel pump itself and the sender are all points to check. First thing to do is stick a fuel pressure gauge on the send line at the intake plenum and get a reading after the car has been sitting for a while. Look for significant leakdown. Could also be a pinprick leak in a line, rubber or metal.

best, whit

[2fast]

I've got the same problem car starts great cold...but warm or hot it takes awhile to crank over,I have just been living with it but would be good to get fixed.

[rommel]

The retro is less than $3 from BMA. Car started great when cold but difficult when warm. The built in check valve in the fuel pump went bad.

Hot Start Problem