ignition help

[Andy H]

Didnt think Id been under the bonnet as soon as this , but welcome to old cars again I guess!.

After a short run today, 2-3 miles, returned home, turned off the car, opened the garage and when I tried to restart,,, wont fire!
Managed to push it into the garage,10 mins later it started.??
let it run for 5 mins and tried again, no start!
checked for a spark at no1 plug and wasnt there first crank , but second time it was there and restarted.
same scenario turn off, wont fire.
checked the coil. voltages ok in and out, but now no spark at the plugs.
So the question is i suppose:
Is the unit behind the passenger headlight the ignition module, and are they prone to dying like this.(like the old '80s Ford escorts etc used to)

Typical, cars cleaned,weathers decent and it wont go!

All help and suggestions appreciated.

Andy.

 

[Big Dave]

I think the first thing to check would be the DME relay.. In the fuse box...Im presuming its a S2 / turbo.???
If its an old relay, they are prone to becoming faulty....
Im sure lots more folk will be along soon...

 

[Andy H]

Thanks Dave,
Checked the DME relay, and it was changed less than 900 miles ago by Porsche after a "no start" call to the AA.seems to be operating ok.
is the DME relay not only for the fuel pump,?? I dont know , my inexperience has me clutching at straws
Just wondering if this has been the fault all along, meaning a dodgy ignition module, the previous owner had only done 800 miles in the last year, and maybe has been getting away with it, ....... until now!

 

[rcsalmons]

If as you say you have checked coil voltage in and out it can only be dizzy cap, rotor, leads or plugs.

Coil LV (in) side In should be a permanent 12v and a switched 0v

Coil HV (out) side loads of volts

Rich

 

[944cabby]

I've had two faulty ignition switches so far - one being the original and the second a new part (non-OEM) from the states (fleabay special!) - the symptoms for mine were intermittant starting - would drive fine for some time then just would just not fire up as you describe.

 

[Andy H]

ORIGINAL: rcsalmons

If as you say you have checked coil voltage in and out it can only be dizzy cap, rotor, leads or plugs.

Rich

Hi Rich,
Again, these parts are all new Porsche items less than 800 miles ago.(at last service)
I have the voltages and 12>0 switch as you described, but nothing at the plugs.
The frustrating thing is when it fires, ,,, its spot on, so i cant see it being anything there,
Ive removed the module and it 'looks' original and a bit tatty, checked the plug and have a 12v supply although I can check any further without a schematic.
A friend has just checked the Bosch number and reckons its the same as a Volvo 940/740 module, so I might do a scrappy hunt tomorrow to rule it out or confirm its dead before a new O.E. part goes in.
I was ssooooo looking forward to a run tonight as well.[&o]

 

[Andy H]

ORIGINAL: 944cabby

I've had two faulty ignition switches so far - one being the original and the second a new part (non-OEM) from the states (fleabay special!) - the symptoms for mine were intermittant starting - would drive fine for some time then just would just not fire up as you describe.

Not tried the switch admittedly, but im getting coil voltage(switch energised), starter engaged and turning,trigger voltage from coil,but no spark at the plugs..

Its just SO reminisent of the old days working on Ford/Vauxhalls during the 80's when modules gave the same faults as Im seeing now.
I hope this isnt the start of a bad relationship [] [8|].

 

[Fen]

It's not a common problem with these cars unless it's the DME relay (which controls the DME - the ECU in other words).

What I spot is that almost everything the previous posters have suggested has been replaced recently. I strongly suspect because it didn't start and possibly the previous owner just got shot of it after spending a fair wedge and getting nowhere with the problem - does that sound possible?

By all means try the ignition switch. I had a dicky one, but by wiggling the key it would work properly which would be a clue. Failing that I wonder if it's the DME itself given everything else that has been checked. My very first 944 broke down on the test drive and had a replacement ECU fitted (from a later car so it ran more boost I later realised) then it did it again after I bought it and got a DME relay (probably all it needed in the first place) and was fine. The point of the tale being a Porsche specialist replaced the DME because they suspected it. Admittedly it cut out when running so not quite the same.

 

[rcsalmons]

Does the rev counter move at all when trying to start? if not could flywheel sensor?

Rich

 

[Andy H]

Thanks for the reply Fen, (to be honest I had hoped you would, no disrespect to the others, as all help is appreciated)

The previous owner was METICULIOUS with the repairs and service, only letting the car down by not looking after anything other than mechanicals.i.e. the bodywork!.(thats my domain)
I dont think he would have knowingly sold with a fault, not that kind of guy.
I have most of the service reciepts and he wasnt afraid to spend money on the car, some are 2k + for services/repairs.
I will spend some time tomorrow and go through it sequencially but im convinced its ignition module related.
Again , I will retrace everything including the new parts fitted to rule everything out.
I DID notice the DME relay was a bit warm on a couple of accasions, so might try a new one as well.

thanks
Andy

 

[Andy H]

ORIGINAL: rcsalmons

Does the rev counter move at all when trying to start? if not could flywheel sensor?

Rich

Hmm, I did notice on 1 occasion it flicked up quite dramatically on tuning on the ignition, but yes, it does move slightly when turning it over.

Incidentally, where is the DME (ecu) mounted,

 

[rcsalmons]

Passenger footwell, behind carpet / wooden board (held by 4 screws).

Rich

 

[Andy H]

Thanks Rich,
Had a very similiar problem years ago with a XJ6 V8 , baffled everyone including Jaguar, to the point that the guy gave up and sold it for spares!
Fault was a dodgy connection at the ECU after a water leak had been fixed (connection dried out and parted from the connector).
My car had a bit of 'moistness' when I got it and ive since had it fully valeted inc carpets seats shampoo etc,after fitting a new sunroof seal, wondering if its something similiar.
Just hope its not like the old 928 rats nest of wiring under the floor panel (goes for a very large vodka to numb the painful thought of a possible wiring nightmare).
The worst of it is Im an electronics engineer, and build electric cars for a big French manufacturer, nothing like taking your work home is there[:'(]

 

[Big Dave]

Just a thought. What alarm / imobiliser does your car have fitted. Is it the "flat blade" near the ignition barrel type.?? Or an aftermarket job.?? The flat blade ones are notorious at breaking .. It could be the flat blade itself. Mine on my 968 came with 3 small "blade" keys, thankfully, as one of them stopped working the other day...
Are they made by Hamilton + Palmer..??

 

[Andy H]

ORIGINAL: Big Dave UK

Just a thought. What alarm / imobiliser does your car have fitted. Is it the "flat blade" near the ignition barrel type.?? Or an aftermarket job.?? The flat blade ones are notorious at breaking .. It could be the flat blade itself. Mine on my 968 came with 3 small "blade" keys, thankfully, as one of them stopped working the other day...
Are they made by Hamilton + Palmer..??

Hi Dave,
the car has an O/E alarm, (flashing door pins etc, but I dont know what you mean by a flat blade, is this like the type of additional key you have to insert every time you use the car (ie on your keyring)??,similiar to the old style jack plug or D shaped key you made contact with on the dash or is it something else??
I didnt get anything like that with the car, its always been only the keys.
After reading the manual, it mentioned something about 5 rapid turns of the key to the right in the door to bypass the alarm,(cant remember the exact explanation) but I tried that too.
Going to spendsome time today and go back to basics , and try and solve it, although having a schematic would make life so much easier.[8|]

Andy.

 

[sawood12]

I would bet a tenner it is your reference sensor. Firstly check the fixing nut is tight - they do have a tendency to slacken off therefore giving you an intermittent output. If the ECU gets nothing from the reference sensor upon startup then the ignition circuit is not energised so you get no spark. The symptoms you describe perfectly fit a loose or failing reference sensor.

 

[peanut]

This is a surprisingly common fault on N/A 944's My 944 Lux suffered from it .

The only thing to do is to patiently wait 15 -20 minutes before trying restarting or it will simply flood the engine again before the excess fuel has had a chance to fully evaporate.

I'd start with the fuel system as it is clearly a temperature related intermittant fault.

My guess would be a leaking injector or a faulty FPR fuel pressure regulator or both

Try disconnecting one of the injectors and see if it then starts next time. If the temporary reduction in pressure allows it to start it would suggest the FPR is stuck closed causing excessive pressure. The excess pressure might cause a injector to leak and flood one or more of the chambers.

If you suspect the FPR get a fuel pressure test done on the fuel rail or try replacing the FPR if you have a spare to hand.

 

[Andy H]

ORIGINAL: sawood12

I would bet a tenner it is your reference sensor. Firstly check the fixing nut is tight - they do have a tendency to slacken off therefore giving you an intermittent output. If the ECU gets nothing from the reference sensor upon startup then the ignition circuit is not energised so you get no spark. The symptoms you describe perfectly fit a loose or failing reference sensor.

That sounds plausible, where is this located? is it easy to get to ?.

Been at it all morning, testing and ruling out as i go along.
I "think" I may have it down to 2 areas although Sawood has given another possible option.

1, IGNITION SWITCH.
When it decides not to start, flicking the ignition on-off several times and the rev counter moves again on cranking and it will fire up.
No rev counter movement on crank = no start !
2, CRANKSHAFT POSITION SENSOR. I have the data/spec to test it now, but cant see/find the damn thing!
Cant understand though ,if this component was faulty/failing, surely it would effect driving and performance.
When its running it pulls like a train and no misfires etc etc
3, REFERENCE SENSOR (do you mean the same thing as point 2 Sawood?), if not where do I find this ?
Car is running/starting again, but I have absolutely no confidence that it is fixed.
I think a trip to Euro is on the cards in the morning for an ignition switch as a first area of attack.

Thanks again to all for the input, it is truly appreciated

Andy.

 

[JamesO]

The reference and crankshaft position sensors are next to each other at the top of the bellhousing. The connectors should be both mounted at the back of the cam tower.
They are variable reluctance sensors one "reads" the teeth of the starter ring gear and the next one picks up a stud on the flywheel.
Following this link may be helpfull :- http://www.clarks-garage.com/shop-manual/ign-02.htm

 

[Andy H]

Thanks James,
I would never have looked to the rear of the engine for the sensors, thats a pretty informative site!

Im now fairly sure the problem is the ignition switch.
If it doesnt start while cranking, I wiggle the key about and it fires up.
Took it on a 'confidence' drive earlier (12 miles) and it drove fine,
if there was a sensor faulty, would it not run like a bag of spanners?
I will go and check the sensors as well to make sure they look ok and are tight.(something else to tick off the list)
no more driving tonight though as its started snowing heavily here just now and I dont fancy an offroad visit into the scenery, so a test drive later isnt really an option,maybe tomorrow if it clears up.

I must say a big thanks to all who have helped point me in the right direction, there will be a a drink of your choice when ever we meet ![][]

Andy.