944 S2 cutting out - help please

[rowey200]

After some guidance / help folks!

There I am, happy as larry blasting back from getting my exhaust sorted.....then, whilst sitting at a junction the engine cuts out and will not start Symptoms as follows:

- a mile up the road before the car cut out the engine momentarily spluttered for a second(as if the fuel has been cut) and then came back to life.
- when the car cut out at the junction I lost all dash lights etc but noticed that I still had power to the hazard lights & stereo etc. The engine would turn over but not start.
- suspecting an electrical issue I opened up the fuse box and made sure that all relays & fuses were properly seated etc - sure enough the car then started as normal. I drove home and it cut out again on the way, starting again after a few minutes following another tinker with the relays. It's now sulking on the drive

A quick bit of internet research mentions that the DME replay is a common fault on the 944 - question is, would a failing DME replay cause the above symptoms? Any advice gratefully received

Edited by rowey200 on Thursday 17th July 08:15

[LarJammer]

if the dme relay fails you will still have dash lights. it could be an ignition switch fault (amongst others). try wiggling the key a bit and see if the problem reoccurs.

eta: does it have an alarm fitted???

[DKL]

I'd try another dme relay anyway.

[SebringMan]

Trying another DME relay may solve the random power issue.

Does your car have an immobiliser? If so I would be adding that to my suspect list. That would potentially cause your symptoms of no dash lights.

[rowey200]

SebringMan said:

Trying another DME relay may solve the random power issue.

Does your car have an immobiliser? If so I would be adding that to my suspect list. That would potentially cause your symptoms of no dash lights.

Thanks for the reply I'll try another DME replay as they sound like a weak point, so it will be handy to have a spare at the very least. A possible immobiliser issue crossed my mind, but I'm pretty sure the car doesn't have one (unless it's somehow disarmed at the same time as the alarm when I unlock the car) - I had a spare ignition key cut the other day it it started the car fine without any immobiliser chip in it etc.

Fingers crossed for the DME

[rowey200]

LarJammer said:

if the dme relay fails you will still have dash lights. it could be an ignition switch fault (amongst others). try wiggling the key a bit and see if the problem reoccurs.

eta: does it have an alarm fitted???

Cheers for the reply. The car still has the factory alarm, no immobiliser as far as I'm aware. I'll bear in mind the ignition switch if it does it again.

[thegoose]

I'd also check the distributor cap & rotor arm.

[GC8]

Ignition switch faults (both early VW type and the series two 928 type) are both far from uncommon.

[rowey200]

GC8 said:

Ignition switch faults (both early VW type and the series two 928 type) are both far from uncommon.

Thanks for the reply. A new DME relay is on its way to me so the ignition switch will be next on the list if the problem persists. A faulty ignition switch could perhaps explain that when the car cuts out I also loose the dash lights even though the ignition is on (if that makes sense).

As an aside, when I fit the new DME replay is it worth pulling the other relays and cleaning up the contacts etc. Also, is it worth using a contact cleaner, or could that do more harm than good?

Edited by rowey200 on Thursday 17th July 08:16

Edited by rowey200 on Thursday 17th July 08:16

[GC8]

Im not the best fellow to ask that unfortunately. I have a massive amount of 944.968 experience, but the bulk of it is from when they were much newer cars.

944s are notoriously poorly earthed too. I realise that your symptoms don't immediately suggest a main earth fault as not everything goes off, but re-earthing everything will do no harm.

[GC8]

[rowey200]

GC8 said:

Im not the best fellow to ask that unfortunately. I have a massive amount of 944.968 experience, but the bulk of it is from when they were much newer cars.

944s are notoriously poorly earthed too. I realise that your symptoms don't immediately suggest a main earth fault as not everything goes off, but re-earthing everything will do no harm.

Thanks for the advice & handy earth diagram I think I'm just going to have to work through a few things until I hit the nail on the head. Like you say, things like checking the car is earthed properly is never going to be wasted time on a 22 year old car.

[rowey200]

Quick update....new DME relay arrived this morning. Before it arrived I removed each and every fuse and relay and cleaned the terminals. Slipped the new DME replay in and the car initially would not start...it cranked over with all dash lights illuminated, but sounded like no fuel getting through. Tried again and it started.....I then proceeded to do about 40 miles this afternoon without a hitch. The car started fine on the couple of occasions that I had to stop. All good so far

Come to this evening and I go to move the car.....it won't start, just cranking as if no fuel (or spark?) again After having a poke around / tapping the DME replay etc (with no joy) I put the old DME relay in and the car started fine I've have since spent some time cleaning up the various earth points I could locate.

It's such a shame as at the moment I just have no confidence in the car....think I'm just going to have to bite the bullet and book it into a specialist for some diagnostics. One thing did cross my mind, I wonder if the battery is on its way out. I read somewhere that the DME reply will not supply power to the fuel pump until the engine is cranking above a certain speed?

As ever, any advice gratefully received

Edited by rowey200 on Friday 18th July 22:19

[LarJammer]

you are not going to get much further without some tools. did the dash fail again?

[rowey200]

LarJammer said:

you are not going to get much further without some tools. did the dash fail again?

I hear ya No issue with dash lights this time, they stayed illuminated as and when they should. It seems to be doing different things at different times, so as you say, some diagnostic tools are now required me thinks

Edited by rowey200 on Saturday 19th July 09:51

[rowey200]

I realised that I had 'Home Start' cover with the AA, so thought it would be worth a shot calling them out to look at the issue. The patrolman reckons one of two things:

- ignition switch
- doggy wiring relating to an old immobiliser etc

Both of the above have been flagged up in this thread, so hats off He didn't want to start pulling my dash apart on the road side (fair enough) so I'll book the car into the garage tomorrow.

The car does have a couple of redunant LEDs mounted in the dash, so it has obviously had aftermarket alarms/immobilisers fitted in the past.

We came across the box below while routing about, it doesn't look factory? Can anyone clarify (it's mounted on the back of the rear passenger internal wheel arch, just in front of the battery. Cheers in advance

[jasongibson]

I've just had problems on my 924S with DME relay/wiring and old alarm issues.

If your problem changes after fitting new and old relays, it sounds like the wiring for the relay, drop the relay board and have a look behind.

When they investigated mine thoroughly, there were the remnants of 4 old alarms and immobilisers.
the wiring into the back of my relay was also rubbish and the relay not always having connection
All had been fitted poorly with crap connections. eventually this had caused problems in my ECU (now repaired)

[LarJammer]

rowey200 said:

- ignition switch
- doggy wiring relating to an old immobiliser etc

Both of the above have been flagged up in this thread, so hats off

i believe i may have mentioned both of those faults. massages ego. not that i tend to agree with any diagnosis an rac man comes up with....

[rowey200]

quote=LarJammer]

i believe i may have mentioned both of those faults. massages ego. not that i tend to agree with any diagnosis an rac man comes up with....

[/quote]

Will keep you posted, it would appear you are bang on the money

[rowey200]

Thought I'd just update this tread

Last month an auto electrician spent some time looking into the issue (car cutting out after 10/15mins of use). He identified that the DME / fuel pump relay was getting very hot, something that he suspected could be being caused by a partially blocked fuel filter (more load on the fuel pump and in turn the replay I guess ). On external inspection of the fuel filter it was evident that it had been on the car for some time. So, starting with the obvious / cheap fix the fuel filter was changed.....and guess what, the car has not missed a beat since I've now done around 500 miles (including a blast down to South Devon at the weekend) since the new fuel filter was fitted and the car has performed faultlessly (before which the car was routinely cutting out after 10/15 mins of use).

In other news 944 flew through its MOT yesterday needing nothing more than the headlight beam adjusting

Next job, a spot of waxoyling!