Car won't start...sometimes
 

I am hoping that one of you has had this issue in the past and can steer me in the right direction. I've had my 1986 928S for a few years now and it's been very dependable. In the last 4 months the car has developed an issue starting sometimes.

Thankfully it is reproducible every time. Here is the scenario:

Start the car cold and drive for a few minutes...like to the gym or store and come back out and the car will not start. Once this happens the car will have to sit for up to 2 hours then it starts fine and will run all day. It's to the point now that I leave it running most of the time.

I have now been stranded countless times.

I have replaced the fuel pump, the check valve on the fuel pump, the starter switch and several other components but nothing seems to work and I'm at my wits end as this is my daily driver.

Thanks for your suggestions.

a quick check would be to floor the pedal and crank till it starts.
If it starts then you have extra fuel being dumped into the intake it would be either the fuel dampers or FPR or the injectors.
My vote is a leaking damper or FPR,
to check, simply remove the vacuum line and smell it for gas.
If you smell fuel, then this would indicate a possible leaking unit,
check all of them as more than one can fail,
report back your findings

Been there and done that Stan. They've been checked out a couple of times. Vac is good through out, fuel pressure is good. CPS is new. Temp II is new along with the harness. Down the leaking injectors/bad MAF now.

Mike, Maybe you've fixed your problem...but if not.....next time you drive it and stop....and try starting it again....stop after 2 tries and check the Fuel pump relay....If it feels hot pull it and install a fresh new #53 relay You may find that it now will work just fine....I had one relay that would do that a few times until I replaced it. It never died and if I put it back in it would overheat and not let me start...I've had other relays up and die...but this one never died just would overheat and not restart. I hope its something this simple.... Just FYI..
Hope it all works out....:thumbup:

Describe "no start." Does it crank well?

Cranks great. Seem to have the typical hot start issue. Except it isn't.

Replace the Temp Sensor II. Could be signaling for a cold start when the car is hot and flooding it.

Dallas + August = Vapor Lock!

I had this issue, it was the starter, wouldnt turn when it was hot. Then years later, almost the same issue, I replaced the starter instantly assuming it to be the same issue... it didnt solve the issue, turned out to be the tired old battery. Let us know what it turns out to be!

-Sam Johnson
78 Euro 5spd
87 s4 5spd

The car actually cranks just fine, it will turn over all day long so it's not the battery.

Sean, what do you think about this Fuel pump relay hypothesis?

Also, in answering the vapor lock theory, it started doing this in the dead of winter so I don't think that is the issue either.

Sean, also what about the Temp Sensor II?

The Temp II and harness are new, the one day I came over I popped in a new relay. We can put another one in just in case the old/new one is crappy.

New parts can be bad. Seems like the point to re-check everything.