First of all: do you have sparks from the spark plugs when you try to start?
Just to prevent extra work…. Check if the EZK is powered up (permamemt 12v and switched 12v, pin 35 and 29). An alarm box can block the 12v so nothing happens…. If someone else messed around with the wiring then anything can happen. Look for non-original wiring.
This is the simplified electrical wiring for the ignition:http://jenniskens.livedsl.nl/Technical/Tips/D/MyTip1344.htm
Check if the coils have 12v on one terminal. This is switched 12v so only there with ignition turned on. By briefly touching the other side to ground the coils puts out a high voltage causing a spark on a plug. You can verify (disconnect power stage first!).
I have seen new compatible power stages that did not work. Are they orginal "Porsche" units? The old ones are really broken?
More troubleshooting is now required. You can meansure with a volt meter but a scope would really be required.
Test with a voltmeter of you see the signal on pin 5 of the power stages change while starting. It should.
Put a scope on pin 23 of the EZK. That should show the diagram as shown here:http://jenniskens.livedsl.nl/Technical/Tips/Pics/TDC%20scope%20beeld.png
Timebase should be like 20ms, it is a low frequency signal as the engine turns slowly.
Send me a picture of the wave form if possible.
With the scope you can check on the EZK outputs for the ignition power stages. I would do that if the input signal is ok!!
You should see the same signal at both power stages, Pin #5.
Only if you see the signal at the EZK but not at the power stages, you need to look at T45. The T45 connector is somewhere behind the relay panel. Don’t remember what it looks like, but expect two shielded wires.
If the injectors have pressure the LH is/was powered up. This will, only happen if the EZK is running and speed signal is detected. But be aware: if the EZK briefly works the LH switches on, LH relay activates, the pump activates and you have pressure in the line. Only if the injectors keep clicking during start you can rest assure that the EZK works and triggers the ignition.
1992 Porsche 928 GTS Midnight blue