John Speake

The WSM shows a trace with the "sine" part as 3v pk-pk. Every flywheel revolution there should be a larger pulse which is where the gap of two teeth are.

See page D28-11 at the end of Vol 1A.

So I don't think your problem is with the CPS.

stuartph

John

My sine wave shown on the screen did not have any higher peaks, like in the WSM

docmirror

Yes it did, you just didn't capture it. Your CPS and trigger wheel on the flywheel aren't the problem.

AO

If your Ignition monitoring relay is not plugged in, the car will not start. THis is the realy underneath the LH/EZK. It has the clear case.

stuartph

Andrew

I have the bypass relay from 928GT fitted, if thats gone wrong how could i check it.

docmirror

I've had good luck by simply bypassing the whole mess. Make a three lead spade jumper and connect it between pins 4, 2 and 5. Look on the relay socket for the pin indicator. It's stamped in the phenolic. Then, you don't have to worry about it while testing. Once the car is running, put the relay back in.

AO

Hmmm... well I doubt the bypass would be bad. It's basically a 3-way jumper. You could try reconnecting the socket to the relay... but I think that's a dead end - especially now that I realize it affects fuel, not spark.

Is spark missing from both sides of the engine? Or just one side?

If both sides, the only things (that I can think of) that would affect spark on both sides are:

CPS (verified good)
EZK - Re-verify that it's plugged in fully and seated properly. It's easy to miss the top part that "hooks" into the module.

If only one side, then it must be a coil, coil wire, cap, rotor, or final stage ignition module.

Other things to consider:
What about a bad ignition switch?
Aftermarket alarm?
Factory alarm? (Try locking the doors and then unlocking them.)

That's all I can think of right now.

stuartph

Doc

Thanks i will try that

Andrew

Last week i had spark both sides this week nothing ?

How could i test the ignition switch

The car does have an aftermarket alarm, which as far as i know cuts the fuel pump and starter, i will check

docmirror

The ign switch has to be replaced. You could try to jumper it too, but after all the crap you would go through to bypass it, you might as well replace it.

Now, this aftermarket alarm scares me. I'm betting it cuts the ignition simply because that's much easier to do on most cars than messing with the injectors. I could be wrong, but most places that install aftermarket alarms and demobilizers simply ground or open the ignition circuit somewhere. I would get this looked at right now.

AO

Not sure how to test the ignition switch. I was just thowing out other points of failure to consider.

frustrated

Got a laserline aftermarket on mine. Wired to break the ignition among other things. Found a bizarre (what appears to be) 3 fused relay box tucked behind the main fuse board. one fuse is alarm related, one definitely prevents ignition and god knows what the other one does. It might be worth checking whether you have something similar?

jon928se

Stuart

If it's an aftermarket alarm/immobiliser fitted in the UK any time in the last 10-15 years or so it will have three circuits to immobilise the car - igition power cutoff, fuel pump cutoff, and starter inhibit. You may well find that your GT also has possibly still connected but no properly functioning remnants of the original H&P alarm system fitted (badly) by Porsche UK when the cars were imported.

I suspect that if there is the vaguest chance that the immobiliser is functioning erratically your best option will be to remove it completely and return the wiring to factory status. This will require some detective work - pull out the boxes and trace the black wiring (alll the alarm wiring will be black) to where it is spliced into the factory loom then identify with reference to the wiring diagrams what each spliced wire does - this will enable you to the reconnect the cut pieces of harness. - Ain't no simpler way I am afraid - it looks daunting but by working methodically through it it's not as bad as it first appears.

docmirror

Yup, that's what I'm talking about. Imobilizers have a ignition cutout on them everytime. Not sure about the FI cutoff on yours, but sure as hell it's got an ignition cut circuit.

Find and bypass that.

stuartph

Thanks John & Doc


I have some luck on my side is that i have a spare alarm system in case the one i have is faulty and i dont mind tracing the wires about if it fixes the car

stuartph

Todays Fun


Check for spark on each bank LH nothing RH a few puffs of smoke

Check alarm wiring and remove alarm just in case, nothing