1986 944 turbo intermittant starting failure

spearscc · 01-30-2005, 06:23 PM

After stopping, say for gasoline, engine turns over fine but will not fire. Wait 15-30 minutes (sometimes less), it starts fine. On a few instances, when clutching for traffic stop (once shifting gears at 50+ mph) engine shuts off suddenly. At high speed it will restart if clutch is released. But if not able to restart that way, the wait period is required. There's no sputtering or loss of power; it's as though the switch is turned off. Otherwise the engine starts immediately and runs great. Several mechanics (one good one with PCA racing experience) have looked at it but it won't fail for them to find the problem. Any ideas?

Lawrence Coppari · 01-31-2005, 02:57 AM

Mine would do the stop for gas thing - no fire at all. The problem with mine was dirty (oxidized) connectors for the rpm sensor and/or the crank position sensor.

These are worth checking out. Mine never quit once running, however.

I'd also carry a spare spark plug with me. Next time it happens, remove a plug wire and attach to spare plug. Crank engine to see if there is spark. Could be a coil problem too.

spearscc · 01-31-2005, 07:03 AM

Thanks, that sounds helpful.

Dan951 · 02-01-2005, 05:39 PM

I had the same problem with my first 951 with 200k on the clock. Clean all grounds and speed and reference sensors. The speed and reference sensor connector is located on the back of the intake manifold there are 2 black plugs.

spearscc · 02-02-2005, 06:42 AM

Thank you!

ronin · 02-02-2005, 08:16 AM

fuel pump relay

also, on your speed and ref sensors, did you recently have the clutch done?

spearscc · 02-02-2005, 08:30 AM

Yes. Late last summer. This problem started soon after.

ronin · 02-02-2005, 08:47 AM

they didn't check the gap and reinstall correctly. this usually isn't something that happens on its own

spearscc · 02-02-2005, 10:19 AM

Thanks.

davearm · 02-02-2005, 01:58 PM

Try replacing the dme relay. Had a similar problem with my son's 1988 n/a 944.
Dave

amschnellsten · 03-16-2005, 08:05 PM

had the same problem. checked the sensors fine, checked every fuel part fine, I realized when there was a passenger the car would never die and always restarted. I realized when i tapped the dme it would die or start. I put in a new dme and works great now. so if it won't start stomp on the passenger floor.

spearscc · 03-17-2005, 05:03 AM

Thanks Everybody!

We think it's fixed now. Apparently it was the sensor gaps, even though two different mechanics checked them ok.