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944 Warm-Start Problems

J

jammy_c

New member

Hi All!

I have a 1990 944 S2 with a strange problem;

The car will always start fine when the engine is cold, but if you drive it for a while (or run at idle until the engine's warm) then turn the ignition off, it won't restart again. It turns over just fine, but really struggles to run.

This is particularly embarrassing when going to a petrol station or shops and you get stuck for half an hour until the engine's cooled down.

I thought it could be something to do with a temp sensor controlling air/fuel mix or timing, but it runs perfectly at temperature until you kill the ignition!

Please Help!



Many Thanks,
James.
 
The essential kit in any 944ers toolbox is a DME relay - have you tried swapping the DME? Known to get problematic with age and costs about £20 from Berlyn.
 
I'm having exactly the same issues.
Ruled out the DME so it looks like an iffy fuel pump.
Clarks is the right place for troubleshooting for our cars!
 
So if it turns out not to be the DME, what is the next step?
If it was a dodgy fuel pump wouldn't it struggle to start from cold aswell? and keep cutting out?
 
JC
I think - and someone may correct me - but at the stage we are at remaining fuel in the fuel line gets vapourised by the engine temp and if the fuel pump is a bit slow then it takes longer to pump more through to start the car.
If the car is cold the fuel is still there hence it starts.
Certainly if I leave mine cranking for 8-10 secs (which seems like an absolute age!) then it will start, I suppose as new fuel finally arrives.
 
That's a good summary, possibly aided by the cold-start settings making the mixture richer and therefore masking a shortage of fuel also. That is (I have always assumed) why leaky injectors (not common on the 944 as far as I can tell) give the same symptoms.
 
I had a similar problem on my S2.
I never got to the bottom of it. BUT, i was going to replace the fuel pressure regulator, + the fuel damper, these items have a diaphragm inside, + i was told it could be "weak" or broke...
I did the usual DME etc, but to no avail...
I hope you get to the bottom of it....
 
Am getting the same problem at present - it must be catching. My cars going in for a few bits of work in a couple of weeks so am hoping the cause will be discovered then. [&o]
 
..there is also the fuel filter to consider, if this is getting blocked and causing fuel shortage. I had an idle problem that later cleared by itself, but changing my fuel filter is next on my jobs to done.
 
I once had a fuel pipe clamped inadvertently when fitting a new filter. The car started fine all the time, but after 30 minutes or so of driving at speed it would start to become starved of fuel and would lose power. With hindsight it was pretty lucky it didn't do itself some damage before it was diagnosed.

Not especially helpful to the diagnosis I'm afraid...
 
Well, i've ordered a fresh new DME and i'll see if that does the trick.
Cheers for everyone's help.

Watch this space...
 
I can't see how it will be the DME relay if it's temperature dependent. If the relay is intermittent it will be intermittent when cold too. It's easy to check by simply bridging the contacts (87, 87b and 30).
 
The relay itself will warm up as well as the engine. If pressed I suspect it won't be the relay also but for the price it has to be ruled out as it's so troublesome.
 
ORIGINAL: Fen

The relay itself will warm up as well as the engine. If pressed I suspect it won't be the relay also but for the price it has to be ruled out as it's so troublesome.
Click to expand...

That's very true, but if the problem is as reproducible as it seems I would be inclined to simply bridge the DME realy when the problem occurs and therefore be able to immediately rule it out at no cost at all. All 944 owners carry a ready-made DME relay cable link in the glovebox, surely?
 
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