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Registered
Join Date: Feb 2009
Location: Park Hills, KY
Posts: 2,459
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what triggers the DME relay?
in the process of resurrecting an 84 944. it had run in the past but it was early this year it was last started. needed a lot of deferred maintenance work to be road worthy. got it to the shop and when we first tried to check, turned the key and the motor cranked. but next time and ever since if you turn the key it does not crank. the dash gauges and lights come on when the key it turned on.
jumper the relay, clean the fuse and got the fuel pump running. then connected the jumper button to the starter and we got it to start. got a new relay, but when I put it in and we turn the key ... nothing. when trouble shooting same issue on my 84 928, same symptom and initially suspected the ignition switch. turns out there is a relay that is triggered by the ignition switch that was bad. been looking at the WSM and the elec info and do not find reference to such a relay on a 944. what I do not know is what triggers that relay? clearly the ignition switch is suspect, but before I dive into replacing that trying to be sure that is what we need to do. I have run wires to the starter solenoid and put a button on the dash to overcome this on a few other cars, porsche and non-porsche. turn the key to on and push the button and they started. suggestions?
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Bob Cox 78 930 clone project car. 87 924S resurrect at some point. 84 928S, Ruby Red linen/brown interior - sold  86 944 turbo my new DE/track car - sold
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09-14-2019, 05:06 AM
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In the Fires of Hell.....
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Get a new ignition switch - that is your problem. This is a known issue on the early cars.
The DME relay only powers the DME unit and fuel pump; it doesn't control the starter. To answer your question, the DME relay picks up a signal from speed/reference sensors when the engine is cranking. If it detects movement, it will power the fuel pump.
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PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost |
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09-14-2019, 01:11 PM
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Registered
Join Date: Feb 2009
Location: Park Hills, KY
Posts: 2,459
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kd,
I know I can alway count on you for answers.... other than dealing with this issue we are ready to put the car on the road. rebuild calipers, new brake lines, new fuel lines, etc. had it running yesterday to get the coolant burped. ran great, no smoke, fans kicked on.
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Bob Cox 78 930 clone project car. 87 924S resurrect at some point. 84 928S, Ruby Red linen/brown interior - sold 86 944 turbo my new DE/track car - sold
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09-15-2019, 05:33 AM
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Registered
Join Date: Feb 2009
Location: Park Hills, KY
Posts: 2,459
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PS. I knew the relay did not control the starter, but did not know what caused the relay to trigger power to the fuel pump and dme.
thanks again.
__________________
Bob Cox 78 930 clone project car. 87 924S resurrect at some point. 84 928S, Ruby Red linen/brown interior - sold 86 944 turbo my new DE/track car - sold
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09-15-2019, 05:35 AM
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944 Turbo
