'83_porsche_944

Hello fellow members.
I have an '83 944 2.5 NA 8v.
I didn't have 12v going to my ignition coil so after finally finding the problem and fixing it i have 12v.
Problem is i don't have spark, i have tried it the regular way and via the jumper system that's explained in a clarks garage article.
Still no spark...
It has the right resistances (0.4-0.6 ohm from negative to positive terminal and 5750 ohm from negative to output terminal).
What could still be the problem?
Could the ignition coil be bad even though the resistances are correct?
The spark plugs are new and unused so that can't be the problem, the only other thing it could be is the ignition cables but i doubt they would be bad?

Anyone have any advice?

Thanks in advance!

austin944

Having 12V at the coil is good, but 12V is not enough to generate spark. You need interruption of the 12V to generate the spark at the coil, and the interruption of the 12V is done by pin 1 of the DME computer. So your no spark condition might be caused by an issue that's upstream of the coil.

You could start here, if you feel you've checked out the coil and downstream components:
http://www.clarks-garage.com/shop-manual/ign-04.htm
"The only problem in determining the ultimate cause of a no spark condition is that if the condition is caused by a problem with the DME computer, there's really no way to conclusively test the DME. The same is true with a no fuel condition. So, what we have to do is determine, as best we can, whether the DME is getting power and whether it's getting all of the correct input signals it requires to run the engine."

Earlier you said that you were removing an aftermarket alarm. How did that go? Was it causing the lack of 12V to the coil, or was it something else causing it?

'83_porsche_944

Hi,

I have completely removed the old alarm system with (i think) no problems. Most of them were those splice connectors or were additional things like a receiver etc..

I don't think it fixed my 12v to the coil, for that i checked the complete wiring and finally found a interrupted black cable and measured 12v at the box, the other end went to the coil so that's finally fixed!

I'm guessing the DME is fine but i'm not sure.

I used the clarks garage writeup where you have to use a cable from the spark plug to a ground and from the negative terminal to a ground with the key in the on position.

I did that and seemed to have spark at the negative terminal of the battery(that i needed to tap to recreate the DME).

Didn't have spark at the spark plug, it seems to me the only problem can be the cable between the ignition coil and the distribution cap (i put the spark plug straight on that) or the ignition coil itself, the spark plug is new and unused.

Any advice?

Thanks in advance
Kind regards
Wout

austin944

So you did the "Ignition Coil Test" here and it failed?
http://www.clarks-garage.com/shop-manual/ign-04.htm

Yes, that would point suspicions at the coil and/or the cable being bad. (I thought by "jumpering" you meant the DME jumper, sorry).

'83_porsche_944

Hi,

Yes i have tried the ignition coil jumper test that you've linked.

​​​​​​Problem is now that here in europe there aren't any ignition coils available (from bosch), i will have to wait to at least the end of the month for that.
How can i check the cables?
Like i said the resistances from the Coil are fine so i'm not sure if the coil is bad or not.

Thanks!

austin944

I have a spare wire that I measured the resistance from end to end and got very close to 0 ohms. The wire should be flexible and not have any cracks.

I feel a little suspicious that the first test you performed had failed. Usually I have to hunt for a while before I find the cause of the problem, and the first few tests don't find any issues. I assume you tested the battery, for example...

'83_porsche_944

Hi,

Just to make sure you know my situation.

The car has been sitting for atleast 12 years and hasn't been registered for about 15 years.

I have bought it and changed: all the filters, all the fluids, fuel pump, timing belt, balance belt, waterpump(new style), rollers, front seals, custom copper radiator, spark plugs, distribution cap and rotor, fuel line going to the fuel filter, fuel strainer, shift bushings (at the transmission and in the car, new battery, removed old alarmsystem, sport throttle wheel, alot of gaskets here and there, AOS system clean, checked all the vacuüm lines, replaced injector filters and have them checked, cleaned out fuel tank and fuel lines, replaced crank timing gear.

Probably forgot some stuff but i have basically touched everything except the insides of the engine block and transmission.

Hope this helps!