94415atocrosswanabe

This sucks my new late 85 944 n/a wont start when hot, it will crank but wont fire, I have to wait at least an hour before it will start again. The hayenes manual says it may be a clogged air filter, so I tried cranking with the filter removed wich didnt help. It also talks about the fuel pump, i havent looked into this yet. I was wondering what other problems it could be. any help is really appreciated.

IceShark

May want to replace the fuel pump and its check valve. I don't think you can buy the check valve alone so probably you have to buy the whole fuel pump.

What happens is the fuel rail soaks up the engine heat and vaporizes the fuel. This pushes the fuel back down the line, past the bad check valve and into the tank. Vapor lock. I don't understand why the fuel pump can't push it out when engine is hot, but it can't.

Olli Snellman

Fuel pressure regulator.


Olli
'88 951

Sasha

It is not the pump - you wouldn't be able to start the engine at all if pump was broken.

Most likely the FPR or cold start valve system. Also check the vacuum lines.

Once you check the vacuum lines, start going after fuel pressure, this would definetely indicate the problem.

Thanks.

SteveB

You may not have a fuel problem at all. Check that out first but consider electrical as well. I had a similar problem with my car. Difficult restart when hot. It was an intermittent problem. I traced the problem back to the DME in the footwell. It had 3 cracked solder points going from the large transistor to the PC board. It was probably loosing contact when it got too warm. I resoldered it and the car has been fine ever since. Not an uncommon problem with the DME.

HTH
Steve '86 951

ribs

I had this problem recently...got so bad that the car wouldn't start cold on 100+ degree days. I replaced my coil with a blaster2 and my DME relay, and haven't had the problem since. You may also try giving your battery terminals a thorough cleaning...I have heard this contributes to the warm no start problem.

Brett944Cab

This will sound truly crazy, but after trying several things for this problem, I have a makeshift solution that has worked for me so far. Whenever mine won't start, I hook up an inductive timing light, grounded to the block. Cranks every time. The timing light was a suggestion from the board for confirming spark signals, but I never needed to, because the light makes it crank. After I fix my overheat, if I still have a start problem, I'm considering a ground line from battery to block to simulate the magical timing light effect.

streck-fu

I had this problem a couple of months ago. It ended up being the fly-wheel position sensor. Before changing it, the car would crank fine without starting (only when hot). If you verify the fuel pump comes on when you turn the ignition switch to the second position and if there is no spark, try the sensor. Either the crank or flywheel sensor can cause this.

Let me know if you want pictures. <img src="graemlins/icon107.gif" border="0" alt="[icon107]" />

Alpine951

Here is my 2 cents.

I have heard it can be related to the crank reference sensor connection. Not the actual sensor but where it plugs into the wiring at the back of the intake manifold. My 86 951 started doing this recently and if I push the connectors together it starts.

94415atocrosswanabe

Thanks for all the help, i havnt tried anything yet, i need some time to mess with it.

Paul C 944

Let us know !!Tell us what you try and what cures it!It would be good info to keep in the back of my brain! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

TheJonesBoy

I had the same thing going as Alpine did. It is easy to diagnose a bad refrence sender. When you crank the engine, look at the tach. If it wiggles, your refrence sender signal is OK. If it doesn't, you just diagnosed the problem.

94415atocrosswanabe

Ok the first thing im trying to do is to check the fuel pump output, fallowing the instructions in the Haynes manual. Problem is it keeps refering to an axhillary fuse block under the left side of the instrument panel. I have looked and I still only know of the fuse panel in the engine compartament. Then the manual says to bridge a wire between fuse terminal 30 and 87B to make the fuel pump run. I can not find terminal 87B.
As far as the reference sender signal, the tack does wiggle when im cranking.
Thanks matt.

94415atocrosswanabe

Oh and also in what footwell is the DME, what does it look like, how big is it. thanks again.

94415atocrosswanabe

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