poor spark cylinder 1 ?

[gaaz911]

so as part of the restoration of my 1986 924s I had the engine out for a reseal etc and the engine is now back in the car however while trying to set the idle/co2 we have found a misfire/poor spark on cylinder 1.

pull the plug lead on cylinder 1 no effect, other 3 leads noticeable engine change,tested the spark at end of lead less than 2,3,and 4

replaced as part of refurb

Plugs and leads
dizzy cap
fuel filter

we changed the plug to another cylinder and it was ok, resistance check on plug lead and coil also ok

so any suggestions for what else to check much appreciated, may be a red herring however the rev counter has also stopped working I am going to revisit all electrical plug connections tonight

cheers

Gaz

[gaaz911]

so disconnected the multi pin plugs in the loom in the engine bay and cleaned up the connections, also black and green on the coil, now tried to start it and it would crank but not fire, I then went to the wires at the coil gave them a wiggle about and it started.

Now this could be a bum steer as the rev counter still not working, so need another pair of hands to wiggle it about as I do a continuity test to the 9 pin plug at the bulkhead ?

[gaaz911]

Now had a bit of result but not sure what I fixed so re-checked the multi pin connectors and the wires at the sensors and also removed and cleaned the injector plug put it all back together and happy days running on 4 cylinders nicely so will see over the next few days if this is resolved or temp fix,


rev counter still not working, I did read a thread on pelican who had similar issues and the rev counter came to life once he took it for a run here`s hoping

Think I`m talking to myself here !

[kdjones2000]

There is a red plug that the wiring harness from the DME to the engine has that needs to be connected to your dashboard wiring harness. The tach signal goes through that connector.

If your other gauges are working, however, I don't think that would be your issue.

Sometimes these tachometers just die - the one in my '87 924S was dead when I got it.

[gaaz911]

Is that a connector under the dash beside the DME ? if so I haven't plugged anything in under their yet so will check thanks for that. this was a replacement tach that was working fine before I took the engine out so hoping your plug is the answer

cheers

Gaz

full thread here
911uk.com - Porsche Forum : View topic - The Silver Bullet-Resto Project

[kdjones2000]

Yes, down near the DME. Don't forget to connect the altitude fuel adjustment unit to the harness as well.

[djnolan]

Do you have a burned through spark plug boot where the spark is jumping to ground?

[gaaz911]

DJ spark plug issue all resolved no problem with the plug boot, KD it was indeed the red plug that was the problem rev counter now working fine thanks for the pointer.

next step is to re-index my torsion bars not looking forward to this little task !

[DannoXYZ]

Seems like you had two independent issues. Tach connector inside and spark-plugs out. What was issue with spark-plug#1 and how did you resolve? Thx.

[gaaz911]

I`m not totally sure what fixed the plug misfire issue the only direct thing I did to the plug was remove and clean the injector plug, we spent all night trying to get the emissions reduced last night from 2.3 with no luck and during this the car cut out a couple of times which we traced to the wiring loom area around the main grommet and after much testing we nailed it down to the 9 pin connector having a bad contact somewhere so we opened the crimps up slightly on all the pins and this solved it although we couldn't pinpoint which individual one was the problem.
Going to dome some tests on the AFM the next couple of days which now looks the culprit for the emissions

[gaaz911]

So managed to do some testing on the AFM today and have an open circuit on the temp sensor/ground which will cause to run rich so replacement AFM needed

[DannoXYZ]

You can replace just the sensor if you wish.
Most likely wiring between connector and sensor got broken.

[dcarlson]

bad distributor cap or wires have caused me similar probs in past..