Discussion
Advice from the knowledgable please.
I have a 95 manual 993 C2, bought 6 months ago having been in dry storage for 10 years prior to my purchase.
I had done a few hundred miles when it cut out while driving, the symptoms are no spark and pulsing of the DME relay, which also causes the fuel pump to pulse (this has been changed for 2 new relays, and a good feed onto the pump which then works normally)
It has been recovered to a garage who look after my cars, they have checked the obvious and the ECU has been away to be checked and found to be good.
The garage is working through the wiring which is a bit labour intensive.
I wondered whether anybody had experienced similar that may short cut the fault finding?
Thanks
S
I have a 95 manual 993 C2, bought 6 months ago having been in dry storage for 10 years prior to my purchase.
I had done a few hundred miles when it cut out while driving, the symptoms are no spark and pulsing of the DME relay, which also causes the fuel pump to pulse (this has been changed for 2 new relays, and a good feed onto the pump which then works normally)
It has been recovered to a garage who look after my cars, they have checked the obvious and the ECU has been away to be checked and found to be good.
The garage is working through the wiring which is a bit labour intensive.
I wondered whether anybody had experienced similar that may short cut the fault finding?
Thanks
S
ras62 said:
DME controls the fuel pump and is independent of the spark side. It needs to see a signal from the crank position sensor to close and start the fuel pump. I would suggest your ignition module is down. It feeds to two coils. Not expensive btw
Thanks, so presumably the ignition module takes a signal from the ECU too? The garage managed to borrow another ECU but it was from a later car and wasn’t compatible so couldn’t be used to eliminate a fault.Orangecurry said:
DME relays can be bad out of the box, though it is unlikely if you've tried 2 new ones. Do you know anyone nearby with a known good relay? It would be very annoying if it was simply that.
For absolute clarity - does the engine turn over on the starter?
The garage had the same thought so ordered another from Porsche to check, I’m sure it’s possible to have 3 faulty relays, but unlikely, and doesn’t explain no spark.For absolute clarity - does the engine turn over on the starter?
Yep the engine turns over, and they’ve now also removed the immobiliser
avaF1 said:
take it back le garage who sorted out your last non running 993 episode............................................?
https://www.pistonheads.com/gassing/topic.asp?h=0&...
It’s the same problem not yet sorted, it’s been on hold over winter as the car wasn’t in use, trying to sort it now for the summerhttps://www.pistonheads.com/gassing/topic.asp?h=0&...
gareth h said:
Advice from the knowledgable please.
I have a 95 manual 993 C2, bought 6 months ago having been in dry storage for 10 years prior to my purchase.
I had done a few hundred miles when it cut out while driving, the symptoms are no spark and pulsing of the DME relay, which also causes the fuel pump to pulse (this has been changed for 2 new relays, and a good feed onto the pump which then works normally)
It has been recovered to a garage who look after my cars, they have checked the obvious and the ECU has been away to be checked and found to be good.
The garage is working through the wiring which is a bit labour intensive.
I wondered whether anybody had experienced similar that may short cut the fault finding?
Thanks
S
I have a 95 manual 993 C2, bought 6 months ago having been in dry storage for 10 years prior to my purchase.
I had done a few hundred miles when it cut out while driving, the symptoms are no spark and pulsing of the DME relay, which also causes the fuel pump to pulse (this has been changed for 2 new relays, and a good feed onto the pump which then works normally)
It has been recovered to a garage who look after my cars, they have checked the obvious and the ECU has been away to be checked and found to be good.
The garage is working through the wiring which is a bit labour intensive.
I wondered whether anybody had experienced similar that may short cut the fault finding?
Thanks
S
ras62 said:
Correct. The DME sends a signal to the ignition module which then triggers the two coils. If you dont see a spark from either distributor then the Ignition module is faulty
BTW the relay chatter you hear is most likely not the DME but another relay being operated by a sticky door entry switch earth
Thanks, it’s definitely the DME relay chattering and causing the fuel pump to cycleBTW the relay chatter you hear is most likely not the DME but another relay being operated by a sticky door entry switch earth
Edited by ras62 on Thursday 11th April 11:31
Pope said:
Crank Sensor
The sensor has likely corroded and squashed inwards; shorting the connections. The initial pulse from the sensor sets off a response that pulses the DME CU and in turn the fuel pump relay.
Unplug the sensor and crank the engine - if the symptoms disappear that's a quick check #thumbup
Thanks, I think the sensor has been tested, but I’ll get it checked againThe sensor has likely corroded and squashed inwards; shorting the connections. The initial pulse from the sensor sets off a response that pulses the DME CU and in turn the fuel pump relay.
Unplug the sensor and crank the engine - if the symptoms disappear that's a quick check #thumbup
Edited by Pope on Thursday 11th April 12:41
Just an update on this one, car is now running, it was the crank sensor, although bizarrely when it was checked with an oscilloscope it showed a good signal, which even more bizarrely continued after the engine stopped cranking!
Anyway 5 hour train journey tomorrow to collect, dead excited it’s like new car day all over again
Anyway 5 hour train journey tomorrow to collect, dead excited it’s like new car day all over again
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