My 944 keeps stopping

[peanut]

well it shouldn't be too hard to spot ... just find your coil and follow the HT lead back to the ignition amplifier. I am not certain that the early 944 has one ? Ok looks like the early 944 coil is under direct control of the ECU which I believe is the 35 terminal ECU Motronic ML1.1 so your car hasn't got a seperate ignition amplifier its built into the ECU which directly switches the coil

 

[peanut]

sam sorry mate I may have been leading you up the garden path , unintentionally. I have never owned or worked on an early 944 which have quite a few differences to the later cars. I have no specific schematics other than the completely and utterly useless Haynes manual. From what I've read of your posts I would say that the problem is likely to be heat related. The engine starts and runs fine for 8 minutes or so which is long enough for everything to heat up to normal operating temperature then it cuts out! The ECU directly controls the coil on early cars and it looks like the ECU is cutting the supply to the coil for some reason and that suggests to me that it is either due to the safety features built into the ECU which prevent the HT working in the event of an accident or the ignition amplifier module within the ECU that switches the coil is getting too hot and breaking down. Make sure that the ECU is securely bolted to the car bodywork at the correct fixing points as the ECU case needs to dissipate any heat through the case to chassis. Check if the ECU case or coil is getting hot when it fails. Double check that you have nice clean earthing for the ECU case or high resistance could cause overload due to excess heat. .

 

[sam116glan]

Ok guys the early 1985 model does not have an ignition amplifier. if I jump the dme relay will I get a spark? as It wont start when jumped. any replies are welcome

 

[peanut]

sam I've suggested the most likely source of the problem but you've chosen to ignore it.[] You've not answered my questions or carried out the checks I suggested so I'm afraid I am unable to assist further .

 

[alwigley]

Hi Sam - yes, the early models are somewhat different from later models and are VERY prone to electrical issues....... I know as I have a few gremlins of my own ! This really sounds as if it's heat related - classically a break in a lead giving trouble when heated up and recovering as it cools down. The DME temp sensor on the front of the block is a common culprit but this really only ultimately alters the mixture. Have you checked the connections to the crank sensor (s) at the back of the block per sulzeruk's post (he knows what hes talking about......) ? Probably worth testing the LT side from battery to coil when the engines hot, if not already checked out, and I reckon you need to retest everything when hot regardless, as this is where your fault lies [&:] Whereabouts in the country are you - perhaps one of us is close by and could lend a hand ?

 

[sam116glan]

Yes I have tested the LT side of the coil when hot and shows 12v or more. I have also run the fuel pump with a separate battery and that still pumps so its not the fuel. Im based in Swansea south wales.

 

[sam116glan]

Hi peanut Im not trying to ignore your sugestions or anyone else I'm not all that familiar with the forum and have just replied in general and not to specific people. The L.T. is still present at the coil when the H.T. stops so I suspect it may be the ECU. it is mounted by 2 bolts and should have 4 so I will attend to that next (friday) Its not getting hot but next time I will try putting a hair dryer on it to see if that causes it it stop!

 

[alwigley]

Too far for me I'm afraid [] It is really beginning to sound like a heat issue with one of the two sensors at the back of the block/flywheel, as I believe one of these is the Hall sensor that tells the DME when to trigger a spark - this is one of the few things that is likely to give you the no spark situation you describe. They seem to be a common fault if you search the forum...... Hope you find it...... Alan

 

[sam116glan]

No Ive already changed the 2 sensors no difference! IM thinking that it must be the dme comp. waiting for a quote to test and or repair. My next test is to apply a hair dryer to it to see if it causes it to stop sparking in less than 5 mins from cold

 

[alwigley]

You've certainly replaced a lot of stuff ! Can't think how you would test the wires running to those sensors for a heat related break, and yes the DME could well be the culprit - sorry mate, early 944's like to do this sort of thing to you........ Do you know anyone you could temporarily swap DME's with, or perhaps you could arrange to borrow one from someone ? Sounds like you need to find a local 944 buddy with whom you can both exchange parts when you get problems !

 

[sam116glan]

A buddy in south wales would be nice anyone out there? I,m waiting for a quote from ecu repairs Ltd of Greenwich london anyone know anything about them?

 

[sam116glan]

Hello to all who have tried to help me over the past 2 months with my 944 stopping after running for 5-10mins. It turns out the problem was with the ecu. this was sorted by reconditioning by ecu repairs of Greenwich. Thanks again for all the sugestions.

 

[peanut]

ORIGINAL: sam116glan Ok guys the early 1985 model does not have an ignition amplifier.

The early 944 does have an ignition amplifier .... it is built into the ECU as I said previously in this thread. The later 944 have a seperate ignition amplifier because it was cheaper for Porsche to produce the ECU and ignition amplifier seperately . The part of your ECU that was faulty was the built-in ignition amplifier . Everything else worked as it should. Glad your car is running again Sam and thanks for updating the thread for the benefit of future readers .