993 non start

[gareth h]

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

[gareth h]

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.

[gareth h]

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.
Yep the engine turns over, and they’ve now also removed the immobiliser

[gareth h]

Orangecurry said:

Pope would have the best range of solutions for this - I would drop him a PM.

Thanks, who’s Pope?

[gareth h]

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&...

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

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 summer

[gareth h]

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

Edited by ras62 on Thursday 11th April 11:31

Thanks, it’s definitely the DME relay chattering and causing the fuel pump to cycle

[gareth h]

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

Edited by Pope on Thursday 11th April 12:41

Thanks, I think the sensor has been tested, but I’ll get it checked again

[gareth h]

Thanks Jon, the cars with Ray West, I’ve passed him the info, he says hello

[gareth h]

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

[gareth h]

Orangecurry said:

Weird coincidence - I'm driving to '5 miles away from Ray West' tomorrow, unfortunately not in the 993. I can pop by and warm it up for you if you like?

You’re a gent

[gareth h]

gareth h said:

Orangecurry said:

Weird coincidence - I'm driving to '5 miles away from Ray West' tomorrow, unfortunately not in the 993. I can pop by and warm it up for you if you like?

You’re a gent

And thanks for putting me in contact with “the pope”