electrical problem

[pauljmcnulty]

Received tonight, any ideas?



[FONT=arial"]Hi. A few months ago i purchased a 944S2 for my son to use. I am a club member but not on the 944 register and as I feel at the moment will not become one preferring to get shot of the car. At my age I am an die hard air cooled man and have 2 x 356, 1 x 2.2 litre 911 and a 912 to play with which give no problems but the 944 has been a bit of bad luck. I would like some help with a technical problem and prefer not to ring Bert Gear at work as it is not a simple problem to explain. I assume you have his e mail number so can pass my request on. [FONT=arial"]The 944 is in super condition, has done about 144k and has full porsche or specialist service history and extensive work is documented. It is mechanically sound with perfect oil pressure and shiny black bodywork. It has obviously been well cared for. When it runs it is ( I must admit) an absolute dream to drive. Some weeks ago it developed an electrical problem which resulted in a misfire, persitent cutting out, a flat spot and engine surging from 0- 3000rpm when you tried to keep it running. I put it into a Porsche "specialist" who changed just about everything except the ecu as no one thing seemed to solve the problem. This included all knock sensors, air meter, TDC sensor, fuel regs, lamda probe, temp senders, relays and even the alternator. Having got it back and only a few days later it was as bad as ever so he agreed to lend me an ecu. On plugging in it ran like a watch. On opening up the old ecu it had signs of a blown component so I put it down to bad luck to have spent the money on all the pther bits. It has been great for a five weeks but the symtoms have returned. This has obviously cost me mega bucks already and I do not feel like taking it back to the dealer . If I do he will claim to have spent the time and the parts diagnosing it so it must be something else. I am not knocking him as he obviously tried everything to cure it [FONT=arial"]Current symptoms are when cold it will start and run perfectly, warm it up and the problem comes back it will flat spot, surge in revs and die and then it will not start. Leave for a while and it will start again and run Ok maybe for 10 miles or so and then play up again. [FONT=arial"]Any idea what it might be? It is causing me to dislike the damn thing so much I am vowing not to buy another water cooled Porsche ever again.

 

[Fen]

Well, if it's the same symptoms as before back after 5 weeks then I'd be looking at the ECU to see if it has the same burned component as the last one. If it does (and it would seem more than a coincidence the last one had it and everything was OK after it was replaced) then something on the car is causing it to burn out. My money would be on the voltage regulator (but that was changed along with the alternator I imagine) or a short somewhere - possibly due to water ingress or a chafing wire. Last suggestion - he isn't doing something harmful like using a powerful charger on the battery while it is still connected or something, is he?

 

[Diver944]

I think you've got to 'persist' with the 'Specialist and take it back again. Ok he has spent time and money looking at the car but he hasn't diagnosed it properly and ultimately hasn't fixed it. This sounds like an annoying and persistent problem but rather than lay the blame with water coolers I would lay it at the 'Specialist'.

Not that I'm getting defensive or anything []

I hope you get to the bottom of it

 

[Guest]

ORIGINAL: Fen

Well, if it's the same symptoms as before back after 5 weeks then I'd be looking at the ECU to see if it has the same burned component as the last one. If it does (and it would seem more than a coincidence the last one had it and everything was OK after it was replaced) then something on the car is causing it to burn out. My money would be on the voltage regulator (but that was changed along with the alternator I imagine) or a short somewhere - possibly due to water ingress or a chafing wire. Last suggestion - he isn't doing something harmful like using a powerful charger on the battery while it is still connected or something, is he?

That was exactly what I thought when I read the post. The first thing I would be doing is taking out the new ECU and seeing if the same thing has happened.

It would be useful to know exactly what component has blown. If it's something on the power side, that instantly says voltage regulator. If it's something in the engine sensor input area, then you should be looking for a chaffed cable or dodgy connection somewhere.

I would have thought that the specialist would have checked for chaffing when he was changing the ECU, as it's easy enough to pull the cable into the engine compartment and have a good look when the ECU is disconnected. It could also be a wire that's got too close to something hot (after all, there are plenty of those in an engine compartment) and has melted, causing a short.

I would also echo what Paul has said. Your specialist seems to be just swapping components knowing that he can charge you for it all, rather than actually diagnosing the problem properly.

I'd lay money on the final problem being tracked down to some charred lump somewhere that'll be dead obvious when it's found. []

If you can't find the source of the problem. I'll give you a tenner for the car. It's obviously a worthless old dog []

Cheers

James

 

[mr brightside]

Hi Paul, the haynes manual drawings for this year car are so bad it's almost criminal but the two systems you mentioned faults with seem to share a common supply from the ignition column. Check for a supply on the red/black wire at the blower motor, the resistance shunts for speed changes are on the ground side so the +ve supply is uninterrupted by other components. The same supply enables the heated rear screen does that work? I can't find exactly where on the column it comes from it's really frustrating the way the schematic's been drawn.

 

[Paul Fraser]

Belated thanks for your help. What I know doesn't work is the blower, windscreen wipers and electrical windows. Need to check the others. Have rechecked the fuses, the wiper relay (swapped this out from another car) and also tried changing the ignition switch at the bottom of the barrel. Do you know the colour of the wire that is supposed to supply from the ignition as I have access to that at the moment?
BTW Well done on getting even that much information from the Haynes. I've looked at that and the Workshop manuals and didn't even get that far: so much for having a Physics degree...

 

[Frenchy]

Ignition switch if no"click" from the starter solenoid ?

 

[EAGLESTONE]

there is nothing. presume new switch needed thanks for reply

 

[Frenchy]

Check out Clarks garage to see which ignition switch terminals are involved and try a short across them with a lump of 6mm cable, not 2.5 etc because of the current draw, burned skin smells awful !

 

[robwright]

Have you cleaned all the connectors to the starter, solenoid and engine to chassis earth at the back of the block? Also clean the earth lead on the battery.

 

[EAGLESTONE]

ok give it a go tomorrow try cleaning first thanks

 

[EAGLESTONE]

hmm ok i will have a look thanks