Why won't it start

[LetsGo944]

Have a 1984 944, ran great for a year then one day wouldn't start. Took it to a shop to get new brake calipers installed (towed there) one of the guys messed with the ignition rotor and was able to drive her home. Next day wouldn't start again ever since pulling straws here since I've replaced alot. So far DME relay, spark plugs, distributor cap and rotor, both reference sensors, battery ground, battery, air filter, oil an oil filter, starter motor, alternator, ignition coil, are all brand NEW. Still nothing any ideas? An yes I've made sure reference sensors were connected properly, an did not move rotor shaft to throw off timing.

[cschmidt]

Good luck, I just went through this on an '88 924, similar I think to your 944.

So first, are you getting spark and/or fuel? I had no spark. I used the DME relay jumper at first to confirm fuel, and also tried starter fluid to insure if any spark was nearby it would catch. No luck. I replaced most of the easy stuff like you have. Also a double check that all your body - engine - ignition grounds are ok. I also then took apart the ECU and resoldered the output transistor, still no luck.

I then contacted ECU doctors in florida. They recommended this test for the sensors / wiring.->


How to test a Porsche 944 RPM and TDC sensor

My car passed this test, so I sent them the ECU. They bench tested it and it failed, redid a bunch of bad solder joints ( for about $350) and had it back in a week. The car started immediately and has been fine since. They will bench check an ECU for $50 or $75, forget exactly.

Good luck.

Chuck

[jeffrsmith]

+1 on ECU doctors

[Jfrahm]

Sorry but these threads just baffle me due to the lack of basic testing. If it does not start it's not really important what has been replaced. Something is not working, what's missing? Fuel? Air? Spark? compression?

Check the spark. It must be strong, able to jump a 1cm gap.
Check the plugs. New does not matter, they could be wet or fouled even if they are only a day old.
Check for fuel, try a small puff of starting fluid to see if you get a rise out of it.
Check the timing, put a timing light on it and look for a spark at the right time and (not extra random sparks.)
Compression is harder to test without a gauge but the engine sounds funny of it's not making compression and you can see if it chuffs hard out a spark plug hole if you can't get an idea of it.

You don't really say what parts are new since the no-start and what has been checked or tried so for all we know you blew the timing belt after you got home, or the rotor was loose at the shop but got halfassed so you could get home and now it's loose again. However if you check the basics you should find the problem or at least narrow it down and checking the basics is what you need to do, and posting how you checked them and in what order and exactly what you found if the mystery persists.