924Board.org

[Blitzkrieg808]

Every November my 924S gives me some sort of starting issues and each year this forum has saved me...This year it turns over just fine but won't fire. I drive this car daily, one morning it took a while to start but once it got going, there were no problems. Two days later, after finishing up at school it took about 10mins to start and was running rough for about 2mins after starting. But again once it got warmed up, she ran like a champ all the way home. Same thing happened the next morning but even after about 20min (battery started to die) it did not start at all. I replaced the DME relay hoping for an easy fix, I even tapped on the position sensors (last year's problem) but it has not started since.

Following clark's garage "No Start" trouble-shooting guide, I have diagnosed it down to a no-spark situation. Went ahead and replaced spark plugs, plug wires, distributor cap and rotor (they were old and seemed like a simple fix)...but still no spark at the plugs. Using an inline spark tester in between the ignition coil and distributor cap, there was a faint spark in the tester light but no spark at the plugs. Using a multimeter I bench tested the ignition coil and read only 0.8V after setting the multimeter to 20 DCV (did this test with the ignition on as well as attempting to start the car). Figured the coil was bad so I went and picked up a new one. After installing the new coil, the situation remained the same: not even 1V from the ignition coil, weak spark from coil to distributor cap, and ZERO spark at the spark plugs. Been searching forums and continuing to follow clark's garage guide but I'm pretty clueless as to what is next...besides replacing the DME computer. I opened up the computer to check for broken solder joints but nothing is sticking out at me...

A question I have is where does the ignition coil ground wire connect to? Could this just be a grounding issue? Other than that I'm just looking for the next best idea on how to proceed, any input would be great! Thanks for reading and Happy Holidays!


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81' VW Scirocco S- Sold
89' VW Golf GTI (mk2)- Sold
87' Porsche 924S- Daily Driver

[jason c]

Check power & ground connections.

Check the speed & reference sensors at their connectors for output (ohm resistance and their voltage output while cranking).
Check the wiring for the speed & reference sensors to the DME for continuity.
The "tach bounce" test only tells you if everything works in the sensor circuit or something isn't working, the above test is for individual parts.

Check the power & grounds to the DME. You should also check resistance in the power wires, the power harness between the DME & battery fails over time. The usual symptom is cold starting fine but runs poor at idle or low rpm when hot, it does eventually fail completely though. Not enough power gets to the DME to run the system.

Check for power at the coil (black wire). Pulse out of the DME & at the coil (green wire)

[KDJones2000]

Have you taken your distributor cap off and looked at the rotor?

There is a bolt that secures the rotor to the camshaft that can come loose, and rotors also can wear out.
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1987 924S SPEC car
Team Toofah Racing
1988 944 Turbo S