Trouble starting 968
 

Happy Holidays fellow 968 lovers,

I have a 1993 Porsche 968 that I've had trouble starting the engine. This is the third time I've had this problem. Here is the scenario the first time this happened. Couldn't get the engine going for a good 10 minutes. Add some fuel, waited for 5 minutes, tried again. The engine came to life. The second time, the same problem. This time I did not add any fuel, waited for a few minutes, tried again. Sure enough, the engine revved up. In both cases, the car had been sitting idle for a while, in the first case for a few months. And once the engine is running experience no further issues. But now, I can't get it started at all. Any help much appreciated.

Same as for any car, check for fuel and spark. Try a puff of starting fluid to see if that helps it catch, best to do this with the airbox top off. Test your spark, ideally with a spark checker to see if the spark can jump 10mm. You can rig something up or buy a checker. Also look for the tach bounce when you are cranking. The tach needle should bounce.

If you have not dealt with the typical DME Relay issue check your DME relay via the jumper described in Clark's Garage and actually if it is not the newer 993 part number go ahead and replace it with a quality part (not the Uro part).

http://www.clarks-garage.com/shop-manual/fuel-05.htm

-Joel.

1 DME relay, Test and replace if reqd.
2 DME harness connector, Check wiring and use contact cleaner harness to clean plug/connector.
3 Tac bounce during cranking, if lacking, chk both crank position sensors and their connections/ wires
4 Chk for spark while cranking
5 Fuel chk for not only fuel flow and pressure, ( fuel pressure) but that the fuel sys chk valve is holding shut during non operation and is not allowing a fuel reverse bleed down back into the tank to happen
6 Cylinder head water temp sensor., Located on top of the cylinder head this comms with the DME and if it goes south will cause a non start condition

When i start my car after winter storage I always remove the DME and crank the motor a few times to get some oil flowing and then jumper the fuel pump for a few seconds to re-prime the fuel rail. Put the DME back in, crank it over and starts right up.
I suspect it's the fuel pressure check valve as mentioned, it's located back near the pump and tank. I know mine has failed, have the replacement just haven't gotten to it. Good luck.

is your battery supplying enough voltage during cranking to engage the relays?

A more detailed description of exactly what's happening will get you better troubleshooting.

Mine had been hard to start lately, lots of cranking without it catching. It turned out to be a bad diaphragm in my fuel pressure regulator which was causing a rich condition (fuel weeping into vacuum line). Trouble-shot it by sniffing the vacuum line attached to the regulator and smelling a strong fuel smell, thanks to advice in this forum.

cheers,
c