My cars says no to hot starts...

[She loved E]

Unfortunately this isn't it: http://www.m42club.com/forums/showthread.php?t=7757

A couple weeks ago the car drove home from work fine. Went to start it 20 minutes later and nothing. It'll crank, sometimes fire and sputter and die, or it won't start at all.

So I did the "mess under the intake" fix and regular driving is much better. BUT I still have the hot start issue. When cold it starts and runs like a champ. :confused:

Ideas:
-Replace the rubber hose/boot from the airbox to the intake. I didn't do it yet, it has some minor cracks and it's the only vacuum hose after the AFM that I didn't already replace.
-Replace the FPR and/or fuel pump. I'm thinking the problem has to be fuel or air related, and the air system has just been done, so this is all I can think of.

Any other ideas? All would be appreciated!

[DesktopDave]

Wasn't there some check valve in the fuel pump that could cause this?  The FPR isn't bad, holds pressure, but a one-way valve in the pump leaks fuel pressure back into the tank?

Sorry I'm so foggy on the details...

I'd also take a look at that DME coolant sensor on the head.  They're pretty reliable, so it's a long shot.  But if it tells the DME that your hot engine is cold the car won't start due to cold-start enrichment.

[roundel318]

x2 on double checking that coolant temp sensor

[She loved E]

x2 on double checking that coolant temp sensor

I assume you mean #6 here: http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=11_1505&hg=11&fg=15

DOH! I'm going to have to remove the intake manifold again to get to that, aren't I?

[DesktopDave]

Maybe test the other end...but it's not much easier to get at the DME, is it?

[She loved E]

Update: I don't think its the DME/sensor because it's not happening only when hot. Even if I kill the engine after romping on it, it will sometimes restart right away; conversely, the other day the car was cold, I accidentally started it in gear (oops) and went to start it again and no dice.

Someone suggested it may be the fuel pump relay, which I'll try first 'cause its cheap/easy. I also bought a spare FPR/fuel pump to try afterward, if necessary.

[She loved E]

I decided to go ahead and overhaul the suspension, seeing as how there's a 99% chance I'll need to order parts for it, so why make two orders from Pelican when I can just make one :rolleyes:.

I started the suspension today, and while I was under the car I cleaned about 3mm of crap off the block above the oilpan, exactly where the crank position sensor is (if its the sensor in that area that looks just like an ABS sensor). I read a few other posts about the CPS causing idle issues... I'm thinking all that sludge around the sensor would melt when hot and gum up the works. So I'm going to clean it up real nice, unhook it and reseat and see if that helps. Wish me luck! (I'll need it )

[She loved E]

OK, changed the cps and fuel pump. Worked like a champ for 2 days and now its giving me trouble again. The car stalled out today while driving and wouldn't fire. Fortunately I got it smogged & registered first.

From reading another thread I *hope* the problem is a bad connection at the fuel pump. I will take the connectors apart and inspect tonight, if I have time. Of course my other car is having problems as well so I need to get one of them fixed tonight. :mad:

[Jorgeconrico]

Nevermind

[She loved E]

bah. it was the fuel pump the whole time. it didn't completely die... there's a loose electrical connection inside the pump, which is why my problem was intermittent. my replacement pump was used, and also faulty (it died after two days of use). after buying a new replacement pump for $200 i'm back on the road

live and learn. next time i'll check for 12v at the pump before chasing it elsewhere (although now i know where every flippin sensor & relay is in the fuel system).