At wits end...

[aapjl]

The vehicle in question is a 1984 944 n/a. The last time I had it out, everything worked fine but then a few days later when I tried to take it out again, a downward spiral began. It would crank over but not fire. After testing for spark and fuel (with an extra DSM injector, yes it had the right resistance) I found that it had neither. I checked the DME and fuel pump relays, both were working fine and the terminals checked out other than the fuel pump doesn't prime, but runs when the terminals are jumped (tried to start it like that, still a no-go). After borrowing an oscilloscope to check the flywheel and reference sensor, I noted that the reference sensor's signal could be best described as about a half-volt of extremely fast oscillations and resembled nothing like the flywheel sensor's signal. At this point, I felt this could well be the culprit and found a used one to replace it with. Unfortunately, nothing changed after replacement. Now suspecting the DME itself, it too was replaced with a used unit, and that hasn't changed anything either, nor does bypassing the anti-theft. Does anyone have any suggestions?

[SolReaver]

Ok, check and clean all the grounds and all signal connections. the speed and ref sensors have old, brittle connectors that tend to go bad with age. Check the main connector to the brain as well. (carefully!)

No spark nor injection, I am thinking signal. The brains themselves usually don't go bad, but it does happen.

[zedsn]

Hi, do you get voltage to the coil but no spark? If so could be reference sensors. You can get a BMW sensor that is the same for about half price of a Porsche reference sensor. Your problem doesn't sound cut and dry though. My 944 just died without warning at a traffic light and the culprit was a reference sensor.

[aapjl]

I was able to test some more things today, and found that all of the reference sensors worked fine in the speed sensor hole, but nothing was working in the reference sensor hole. I also swapped sensors between the speed and reference harness connection to establish that the wiring was ok (and it was). After inspecting the flywheel through the top inspection hole I found that the small set-screws that trigger the reference sensor had been ground down flush with the flywheel by....something? This obviously explains why I was getting nothing from the reference sensor, but how in the hell could I have driven it once, parked it, and then return to this? Supposing I pulled the bell housing and flywheel/clutch assembly off, where would I find the spec height of those screws to replace them?

[zedsn]

Hi, one of the reference sensors must have slipped down somehow and wiped out the set screw. You might want to unbolt the sensor block and inspect and see why. Sorry can't help you with set screw fitment.