Running issue/car keeps cutting out.

[Asiangunner]

Running issue

Hi guys, 
Hope someone can help diagnose the following:
The cars been running like a dream but I started my 83' 944 up yesterday and let it idle for about ten mins while I was chatting to a mate, I got in and went to pull off and the car just cut out straight away.
I checked the fuses, they were fine, waited about 10-20 mins an the car started up. I guessed there might have been issue with fuel pump relay as car was turning over but just not firing up. 
I got 2 mins down the road and it cut out again. I got it recovered home. While I was waiting for recovery I did try start the car and occasionally it would fire up but soon cut out just at idle. 
I went to eurocarparts this morning and bought a new DME (aftermarket version they sell) took it home and fitted it. Car fired up an I guessed all was well again. I drove for 5 mins and once again the car cut out just like yesterday. Cars currently parked up a mile away from home, I think it will start when I go back to it but I had to come to work now. 
There is plenty of fuel, recently fitted new dizzy cap, rotor arm, spark plugs, ht leads, fuel filter, oil filter, oil crank sensor, coolant temp sensor , battery and connections are good so I'm happy that's all good. 

The rev needle bounces on trying to turn the engine over. 

Any ideas guys? 

 

[DarrylH]

ECU?

I had a fault with mine when I first got it and it fired on the dodgey ECU but cut out. Changed it and it's been fine since. Bit of an expensive option if you aren't certain though!

 

[bmnelsc]

Ignition coil can fail when hot and then work "sort of" when cooled enough. They shouldn't be too expensive as there are no moving parts. See the following from the Alternate Parts Fitment page on the 944 FAQ section in this forum:

START COPY
Meh, Beru make OEM parts for Porsche or at least they used to!

I don't know if the 944 shares its ignition coil with a 928 but if so, the next bunch of information may be quite relevant on this thread.

quote:

Bosch Coil Catalog tells me that the part number is shared with Volvo V6s, Porsche 928s and Pug 604s so it can't be that special

END COPY

 

[peanut]

try making up a simple 3x wire bypass and fitting it in place of the DME relay.
If the car then starts and runs normally it will eliminate a lot of suspects and narrow down the areas you need to test considerably.
Clarkes garage workshop will tell you how, or o a search for 'no start' on the forum.

 

[Asiangunner]

ORIGINAL: peanut

try making up a simple 3x wire bypass and fitting it in place of the DME relay.
If the car then starts and runs normally it will eliminate a lot of suspects and narrow down the areas you need to test considerably.
Clarkes garage workshop will tell you how, or o a search for 'no start' on the forum.

I can this a try mate but will i learn anything from it as i've tried a new Relay and have the same symptoms.

I just went to where the cars parked and tried starting it to get it home, the car started up but quickly cut out and now the battery is too low to turn over.

Slightly annoying!

The ignition coil being faulty could make sense, what are the normal symptoms of a faulty coil?

As i've changed everything else on the ignition system as in leads, caps, starter, plugs could all that have strained the one thing i've not changed?

PS...How would i check for a faulty ECU?

 

[peanut]

ORIGINAL: Asiangunner

ORIGINAL: peanut

try making up a simple 3x wire bypass and fitting it in place of the DME relay.
If the car then starts and runs normally it will eliminate a lot of suspects and narrow down the areas you need to test considerably.
Clarkes garage workshop will tell you how, or o a search for 'no start' on the forum.

I can this a try mate but will i learn anything from it as i've tried a new Relay and have the same symptoms.

of course you will ! .....well at least i will learn something from it []....because I understand the Bosch fuel injection and Engine Management System. the 3x wire bypass does a lot of things that the DME relay doesn't do . Thats why it is called the DME relay bypass.

If you tell me whether the 3x wire bypass makes any difference or not I'll then be able to tell you a whole heap of things it could be and a whole heap of things it can't be .

Fitting a new relay doesn't tell you anything .

Fit the bypass then if it doesn't start and run normally ,check for a spark at the plugs and fuel in the cylinders ( check spark plugs )


Remember the engine has to crank at a minimum of 200rpm before the ECU grounds the injectors and coil pulsing so charge your battery or use a good jump battery

 

[Asiangunner]

Hi Nick,

I finally got a chance to have a look at the car today, I haven't touched it since last posting on here.

I first jump started the car and let it run/idle and just like before it cut out after ten mins or so.

I fitted a 3 wire jumper and the car does fire up but quickly cuts out. (87 87b and 30)

I followed the Clarks guide for the jumper and when i put the spade in to 30 I don't think i can hear the fuel pump energize.... i'm not sure if i'm just being deaf

 

[Asiangunner]

Just to add, there is loads of fuel in the car and with the bypass the car cut out after just a few seconds.

EDIT

Just pulled up the boot carpet and layers covering fuel pump and still no sound from the fuel pump.

Also after reading a therad where you helped JuvUk I thought i'd add that i replaced my FPR late last year mate.

I did that when trying to diagnose rough running which turned out to be a misfire from poor HT leads which i replaced.

 

[peanut]

I have decided that I cannot spend the time on the forum that I would wish to anymore, due to working 15x hour days 7x day weeks as a full time carer .
However as I started helping you with this issue it would be unfair to just abandon it so I'll try help when I can but hopefully others will chip in when they can.

First of all thanks for testing with the 3x wire bypass that has told me a lot.

You wouldn't necessarily hear the fuel pump when you fitted the 3xwire bypass because the fuel injection system was already fully pressurized from the last starting attempt.

I have the Occupational Therapist arriving in a few minutes for Pop but I'll get back this afternoon or this evening ok

 

[Asiangunner]

That's brilliant mate I do feel pretty lost for ideas at the mo, really appreciate all your help and advice.

 

[944 man]

It sounds like the fuel pressure regulator, although problems like this usually sould like any number of possible things. I suspect that it will contiune after the bypass, when Peanut will no doubt suggest the same.

 

[peanut]

yep I think you've hit the nail on the head with fuel pressure Simon but why ... thats the question.

Its most likely to be the FPR but it could also be the non return valve in the fuel pump but it could just be insufficient fuel delivery from the fuel pump due to a faulty pump or blocked filter etc so that there is enough pressure to start but the fuel pressure then rapidly falls until the engine dies.

It could be over-pressure due to the FPR ...which would shut the ECU down.[] Easy test for over-pressure is to pull off one of the electrical connectors to a fuel injector and see if it then runs allbeit roughly without cutting out.

I'd put a fuel pressure gauge on the fuel rail so that I could check the fuel pressure and do a leak down test plus watch the pressure when starting the car to see if the pressure changes when it cuts out. It only needs to be a bit of garden hose pipe with a tyre pressure guage stuck in the end and a couple of jubilee clips.

 

[Frenchy]

Nice to see you back with some helpful advice Peanut [][]

 

[peanut]

thank you Frenchy its good to be back amongst good cyber friends even though its just to try and help with this outstanding commitment .

I hadn't realised that I had so many good friends on here which makes me feel a bit guilty for walking out. I'll take some time out and see if I can find a way to look in from time to time and keep all you hooligans in place lol.
take care
Nicholas John

 

[BenEngland]

I had a similar problem which progressively worsened over a number of years.
Eventually being found to be dry/cracked solder joints in one of the ECU's.
Please see my description in the technical articles section of thev 944 forum.
'Engine hunts & serious backfire - problem solved'
I am not saying that is exactly the same fault but worth a read before you try replacing everything under the bonnet, if it were an ECU fault depending upon which connections were effected it may result in the symptons you describe.
And yes the car did cut out unexpectedly, eventually to the extent that I did not dare take it out even for a run round the block.
Hope this is of some help.

Regards Ben England

 

[944Turbo]

ORIGINAL: peanut

thank you Frenchy its good to be back amongst good cyber friends even though its just to try and help with this outstanding commitment .

I hadn't realised that I had so many good friends on here which makes me feel a bit guilty for walking out. I'll take some time out and see if I can find a way to look in from time to time and keep all you hooligans in place lol.
take care
Nicholas John

hope the other commitments allow it!

 

[944Turbo]

If its an early car it is relatively common for there to be corrosion under the battery letting water in IIRC the battery is where the fusebox is on later cars - just above the ecu in the passenger footwell. might be worth checking its dry down there, especially as a couple of others have had similar issues with ecu faults,
Tony

 

[Outrun944]

This sounds familiar.

I'm going to say as well - probably ECU

There are ECU test centres around the UK (just don't use the one I did in Heanor / Nottingham!)
Here was my topic - see if anything sounds familiar and some great advice in there from Peanut as always - http://www.porscheclubgbforum.com/tm.asp?m=706395&mpage=1&key=

 

[Asiangunner]

Nick, Simon, Ben, thanks for the replies guys, i've not had a day off since last posting so not had a chance to look at the car.

That plus my caliper rebuild on a 996 is slowly turning in to a job that makes me feel like i've bitten off more than i can chew..... waiting for a helicoil kit to arrive tomorrow.

I will continue investigating the 944 from tomorrow and update asap guys, thanks again for the posts.