Starting problems

[porschedavid]

Hi porsche 928 s2. Took porsche out for drive yesterday. Got it up to operating temperature. I was driving along and it just cut out on me. I tried to start it again but all it was doing is the engine was turning over but not firing. I left it for 3 hours I went back to it and it started first time. Started it today from cold it run for 5 minutes and cut out on me and it did the same as the day before, the engine was just turning over and not firing. I left it for 3 hours again and it started first time. Any ideas?

[Dean_Fuller]

Ignition switch ? I have had it act the same way on my 89 S4.

[harborman]

Originally Posted by porschedavid

Hi porsche 928 s2. Took porsche out for drive yesterday. Got it up to operating temperature. I was driving along and it just cut out on me. I tried to start it again but all it was doing is the engine was turning over but not firing. I left it for 3 hours I went back to it and it started first time. Started it today from cold it run for 5 minutes and cut out on me and it did the same as the day before, the engine was just turning over and not firing. I left it for 3 hours again and it started first time. Any ideas?

Is it getting fuel? Does it have spark? Is it flooding? How are your ground connections? How are the battery connections? Do you drive it frequently? How many miles on the car? What has been done recently to it? Is it maintained? How is the fuel filter and pump? I would suspect an electrical issue if it just cuts out instantly, but could be other issues. Give a brief history of the car.

[928gene928]

Went through the exact problem your having, and tried all the previous suggestions. It turned out to be the ignition relay. Off hand I forget the relay number, but I have not had a single problem since I change that relay.

[928 Go Go Joe]

Happened to me. Ignition coil. Check the primary (low voltage) circuit from the coil to the distributor with the key on. If there's no current, the coil's probably bad.

[Mrmerlin]

Go Go not so fast here depending on the year of the car your working on.
coils dont usually fail there are usually other reasons for not finding spark.
From the info provided the higher probability of failure would be the resistors on the right hand fenderwell VS a bad coil .
That said the most likely failed part is either a fuse or relay, OR if you have a green wire make sure its new

[Alan in AZ]

Always tell us the exact year first! - Start with the most likely, easiest to test and cheapest to replace items.

Check all the fuses (with a DMM), Change all the most likely suspect relays: Fuel Injection, Ignition (spark) - cheap to do.

If it fails again immediately check you have ignition (15) on when the ignition switch is in the ignition position. Have someone listen to see if you get a fuel pump priming pulse when you first turn the ignition on. Only replace the Fuel Pump relay if it is known to be bad ($$$) but you can bypass it with a 30/87 bridge for test purposes.

Alan

[Landseer]

Need to know if its a Euro or USA version.
Need to know if there was any stumble / partial start when cranking.
If not done recently, pull CE, polish, re-fuse.
Same with key grounds.

Injection relay is also costly on these, but replace it if it has any significant age on it.

Heat soak causing movement in wiring can trigger a short in an injector plug, that takes-out all the injectors.

We've seen in the Ljet cars 4 cylinders loose injector pulse with a corroded wire inside brain box leading to the one of the two internal final stage ampls.

We've seen what appears to be heat soak / intermittency with the LH Jet (Euro S2) when there is a bad Crank position sensor.

I now always replace all sensors, fuses and key relays when resurrecting one of these cars, along with fuel pump and clean all grounds. Lot less frustrating.