No HV spark
 

I purchsed a 1987 944s a few months ago in non running condition. I have it all together but have no high voltage spark. Have power to fuel pump, injectors and coil. Does anyone have any ideas? I even tried a new computer and DME relay. Car alarm is disarmed.

I had a similar problem a few weeks ago. With ignition key on, you should have 12V to coil. When I tapped the green wire on my coil to 'ground' I got a spark, so coil was good. Problem was the TDC reference sensor (even though the resistance readings were good and with a volt meter on AC scale I did get pulsing from it while cranking).

I had also cleaned all the coil, battery, starter motor, relay, DME computer harness plug, sensor plugs and applied dielectric 'tune up' grease to all these connections. But I'm sure you did this already since the car is a 16-year-old Porsche!

The reference sensor you are referring to, is it the one on the flywheel or the one on the cam hosuing?

Correct me if I'm wrong, but the "S" models used the same sensor for TDC & RPM? If not, I would guess the TDC would be on the Flywheel, and the RPM on the cam shaft. Best way I think you could tell is RPM's read the teeth, where as the TDC sensor will count a single mark as it passes. RPM sensor is what triggers your HV spark condition.

The S models use a cam shaft sensor and a flywheel reference sensor. Just to make sure I understand you, the cam sensor is also called a RPM sensor and triggers the HV spark. It makes sense to me. The cam shaft sensor is located behind the cam shaft pulley where it senses when a opening in a metal plate passes by it. My assumption is that when it senses the opening it tells the cpu to fire.

yes, that's your TDC sensor. The two are the same sensor type on my '84. One counts the teeth on the flywheel and that's the rpm, the other detects a pin mounted on the flywheel, that's the TDC sensor. TDC initiates the spark, RPM controlls things like fuel pump etch.

also on mine, the sensor and pin have to be .8mm clearance between the two, and the pin has to be 5mm +.05mm leeway. it's hard to get it set correctly. your set up sounds easier