Not starting

[kcbart]

I've came back to 944 ownership after a gap of 20 years during which time we had to have sensible cars for transporting children, dogs, etc. I've had the current one for a year and no problems until now. 3 weeks ago on a Monday morning after not using her all weekend she wouldn't start. Checked and cleaned dizzi and spark plugs, still not starting. Put in the spare DME relay, no difference. Checked for a spark and there is a good spark. Bridged the DME relay connections and the fuel pump runs. I attached a tube to the end of the fuel rail and plenty of fuel comes out. It seemed the most likely thing to be was the fuel pressure regulator, so got a new one. It wouldn't start immediately, but after a long time eventually did with white smoke coming out the back for a short while. I took it for a spin but it was very hesitant if I tried accelerating quickly from low revs, but over 3000 revs was perfect. The next morning it started straight away with no signs of hesitancy and has been running perfectly until now.
This morning after not using it over the weekend it wont start again. As both occasions followed very wet weekends I have checked behind the board in the passenger footwell and no signs of water. I have flicked the injectors with wires from a 9v battery and they click. I checked the voltage on each of the terminals going into the injectors with the ignition on and have 12 volts on each - I read somewhere that one should be 12 and the other zero.
I would appreciate any ideas where I go from here.

Just remebered - taco bounces when trying to start

 

[alwigley]

Have you been having problems with the idele speed - either too high or too low, perhaps affected by engine and/or external temperature ? Could well be a sensor failing giving intermittent readings - first point of call might be the DME temp sensor - unplug it with the engine running and see if anything changes........ There is a very good section in the workshop manual covering troubleshooting of the Motronic system, which gives details of how to test many of the other main components.

 

[kcbart]

I have had no problems with idling - just under 1000 revs and steady. Unfortunately I can't check anything with the engine running as she won't start at the moment, but I will look at the manual tonight as suggested. One other thought - could a faulty immobiliser cause this. I have the one originally fitted which you have to put in a slot behind the steering wheel, it beeps a few times and then allows you to start. It's a nuisance especially in the dark when you can't see the slot! Is this easy to remove or bypass?

 

[Lowtimer]

I am hopeless with electrics, but I can't help thinking that if the immobilisers fitted to Porsches were easily removed or bypassed, there would be no point fitting them in the first place.

 

[zcacogp]

A faulty immobiliser can cause all sorts of ills, and if you can, it's worth taking it out of circuit to eliminate it. BUT if the immobiliser was faulty then you'd be unlikely to have got sparks/fuel in your diagnostic tests. You'd also be unlikely to have made it run at all, unless it is an intermittant fault with the immobiliser. None the less, I suggest that removing the immobiliser is a good idea, just to be sure it is not a contributory factor. Oli.

 

[pauljmcnulty]

I am hopeless with electrics, but I can't help thinking that if the immobilisers fitted to Porsches were easily removed or bypassed, there would be no point fitting them in the first place.

But they were decent enough for standard-fit at the time. Mine had all the original, and some aftermarket, stuff stripped out and a new system fitted, by a previous owner. £300 well spent and it helps the insurance.

 

[zcacogp]

I don't think there were any standard-fit immobilisers to 944's. The one that crops up most often (but not on all UK cars) was fitted by dealers, and is made by Hamilton and Scott. (Or something like that.) It wasn't factory fitted, and wasn't fitted to all cars - just most of them. Mine had one. But it failed, and left me with a non-starting car at Sunningdale railway station, with a fairly important work do to attend. Suffice it to say that wiring it out of circuit took about 1/2 hour with little more than an AVO meter, a torch and some chocblocks. And that was while wearing a suit, with limited working space (but was still quicker than calling the RAC and letting them fix it.) A full modern Thatcham Cat 1 alarm and immobiliser is a good investment. Oli.

 

[kcbart]

Thanks for your thoughts. Oli, I don't think my electrical skills are anywhere near yours - I wouldn't know where to start. So unless there's an idiots guide to removing the immobiliser I think I'll have to get an auto-electrician in.

 

[zcacogp]

An auto-electrician should be able to remove the immobiliser. Or even an immobiliser fitter - you'll need to get a replacement fitted, and the guy fitting the replacement can remove the old one while he does it. An alternative would be to get a diagnostics person to have a look. It will cost more to pay them to remove the immobiliser, but they should be able to diagnose the non-starting as well. Which the auto-electrician may not be able to do. Oli.

 

[kcbart]

I have taken your advice, Oli, and have arranged for someone to come on Thursday. I'll let you know how it goes.

 

[zcacogp]

Oh bu99er. Taken my advice eh? Don't think anyone has ever done that before. [] Please don't blame me if it all goes wrong! Oli.

 

[Eldavo]

Although he'd be in his rights to call you a bar steward then

 

[zcacogp]

Oh yes. But then most people do that most of the time anyway, so it would be nothing new! Oli.

 

[peanut]

ORIGINAL: zcacogp Oh bu99er. Taken my advice eh? Don't think anyone has ever done that before. [] Please don't blame me if it all goes wrong! Oli.

its going to be all your fault Oli whatever happens [] Keith you have done all the right tests and provided all the right information. I would ignore the immobilsier for now as you are getting both spark and fuel pump and starter motor so it must be ok . You have a strong spark and the injectors are getting a 12v supply but is your engine receiving sufficient fuel ? Going on what you have said about the white smoke, hard starting and rough running i would say no. Your car is a late model . I'm pretty sure it has a cold start injector yes ? Did you flash the cold start injector with the battery ? If yours has one it is near the front of the engine on the end of the fuel rail. Have you tried squirting plenty of easy start into the inlet whilst cranking ? If it then fires it will confirm insufficient fuel delivery. The ECU pulses both the fuel pump and the ignition system to ground so it would be advisable to clean the main earthing points GPl, GPll & GPlll You are getting a spark so concentrate on the fuel delivery. If after cranking the engine for 30 seconds with a DME bypass fitted and still no start, your five injectors should then have wet the spark plugs ? My guess is that the injector solenoids are still sticky and the injector filters may be partially blocked. Once the car starts and runs they will self-clean within 15 minutes or so. I would re-flash all 5x injectors at least 20 times each with the 9v battery and clean the main earthing points GPl ,GPll, & GPlll (so that the DME and ECU have good earths). Then file the spark plug electrodes to a sharp edge to assist strong sparking. I actually pre-heated my plugs in the oven before fitting . Carefully remove any carbonation on the dizzy electrodes and file to a nice sharp edge with tiny file. File the rotor edge or rub the edge on wetndry and try again

 

[zcacogp]

Nick, Great diagnostic write-up (faultfinding, and writing it up, is something you seem to be very good at.) However, he said that there was lots of fuel available from the fuel rail, and that when it runs it runs well over 3000rpm. Surely this would rule out any fuel starvation? Or am I wrong in this assumption? Oli.

 

[peanut]

ORIGINAL: zcacogp Nick, Great diagnostic write-up (faultfinding, and writing it up, is something you seem to be very good at.) However, he said that there was lots of fuel available from the fuel rail, and that when it runs it runs well over 3000rpm. Surely this would rule out any fuel starvation? Or am I wrong in this assumption? Oli.

I thought the op's current problem (correct me if i am wrong ) is that the car won't start ? There may be lots of fuel at the fuel rail but that is no help if a) there is no fuel pressure and b) the fuel is not getting through the injectors into the inlet and the cold start injector isn't working. Hence my suggestions . I find its best not to assume anything and do a proper sequential troubleshoot. That way you miss nothing and its more informative and diagnostic for those of us sat 100's of miles away in our armchairs.[]

 

[kcbart]

An update. Having done most of what was suggested and reaching the limit of my capabilities I asked our local independent garage man to have a look. He checked everything and said the problem was caused by a weak spark. New dizzi cap, rotor and leads and she's perfect again. He said that checking for a spark the way I did, i.e. sticking a screwdiver in the end of the lead and laying it on the engine, can give a false impression as the high pressure inside the engine makes sparking more difficult, so what might appear to be a good spark on the outside, isn't on the inside. So the method I have been using for the last 35 years is no good! What is the best way for a DIYer to check the spark? Many thanks for all your help on this - I have certainly learned a lot.

 

[peanut]

glad to hear that your 944 is up and running again. I use a spark plug tester which I think costs £5.00 from Halfords or any car accessory shop. Here is one for under a fiver on Amazon [link=http://www.amazon.co.uk/Silverline-633982-Ignition-Spark-Tester/dp/B00157O4YK]http://www.amazon.co.uk/Silverline-633982-Ignition-Spark-Tester/dp/B00157O4YK[/link]