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What's going on - won't start or cuts out

T

T3rra

New member
I know off a hg that failed during an mot they leave the cars running for a hour on the spot and if something fails cars can over heat in noticed. Hopefully that's not the case here
 
I got a call from the garage to say the good news was my 944 had passed the MOT no problems, the bad news was that it was now refusing to start!!

A couple of days later I got a call to say it was now starting but they hadn't actually fixed anything!
I picked it up and got it going ok but about 5 miles from the garage, the engine just cut out and I coasted to a halt.
I started thinking about what the problem might be and when I tried re-starting, it started ok so I drove home.
The next day I started it and left it running for at least half an hour with no problems.

This car has never refused to start/cut out before.

The only work it has had recently was I replaced the temp sensor for the dashboard gauge.
This bit of the wiring loom also contains the wires to the DME's temp sensor.
If I disturbed this, would a bad connection cause the symptoms above?

The garage reckoned it was the after market alarm/immobilizer.
The alarm people (Autowatch) say they rarely see a faulty alarm/immobilizer system!

Any ideas gratefully received . . .
 
If it turns over but dosent catch and the tacho bounces - DME relay, if it doesnt bounce - crank sensors, would be the first thoughts.
 
ORIGINAL: A9XXC If it turns over but dosent catch and the tacho bounces - DME relay, if it doesnt bounce - crank sensors, would be the first thoughts.
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Not really up to speed on 944 tech yet as my 924 doesn't have all these gizmos. Are both the DME and crank sensor (is there more than one?) capable of working fine sometimes and then not working. What effect would a break in one of the wires to the DME temp sensor have?
 
Its the 'DME relay'. The DME is the ECU - Digital Motor Electronics in English. Yes, the DME relay is quite likely to come and go for a while. The crank sensors less so in my experience, but the wiring and particularly the connectors are troublesome.
 
ORIGINAL: 944 man Its the 'DME relay'. The DME is the ECU - Digital Motor Electronics in English. Yes, the DME relay is quite likely to come and go for a while. The crank sensors less so in my experience, but the wiring and particularly the connectors are troublesome.
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Yes DME 'Relay' is what I meant, sorry - I presume its something I can carry as a 'get me going again' spare. This would have the advantage, if it worked, of then knowing that that had been the problem - otherwise the list of possibles is almost endless.
 
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Its always best to keep a new and tested one in your glovebox. For fault chasing, Google "Clark's Garage" and follow the procedures there. Its an invaluable site. New parts will have a 993 part number btw.
 
ORIGINAL: 944 man Its always best to keep a new and tested one in your glovebox. For fault chasing, Google "Clark's Garage" and follow the procedures there. Its an invaluable site. New parts will have a 993 part number btw.
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Just checked the car and the relay appears to be dated 1987 which would make it an original factory fit!! Maybe it's time I treated it to a new one - or at least have a spare in the glove box. It seems strange that sometimes it works and sometimes not - I thought relays just failed and that was it. Fraserpart appear to do a DME Relay 993 615 227 01 for about £18 so that's not too expensive.
 
DME relay problems can be tricky to identify because each relay does something different, so the symptoms suggest either ignition or fuel system failure, depending on which bits goes wrong. This is a little vague, so I will explain: when you turn on the ignition the first relay is energised which turns on the DME. When starting, when the motor spins at or above the required speed, the DME then energises the fuel pump relay allowing the engine to start. Both of these relays are housed within the one small 'relay' and either can fail intermittently or permanently, singly, together, or in combinations...
 
ORIGINAL: 944 man DME relay problems can be tricky to identify because each relay does something different, so the symptoms suggest either ignition or fuel system failure, depending on which bits goes wrong. This is a little vague, so I will explain: when you turn on the ignition the first relay is energised which turns on the DME. When starting, when the motor spins at or above the required speed, the DME then energises the fuel pump relay allowing the engine to start. Both of these relays are housed within the one small 'relay' and either can fail intermittently or permanently, singly, together, or in combinations...
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Thanks for the nice clear explanation, I realise this is a bit of an old chestnut on this forum but reading old posts, there never seems to be a case that exactly fits your particular symptoms especially when those symptoms are intermittent. I couldn't see a test procedure for the relay on Clarkes or is it test by replacement - assuming the new one works?
 
Hi Vince Hopefully this link to clarks garage with give you the info you need http://www.clarks-garage.com/pdf-manual/fuel-05.pdf Pete
 
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