Engine Problem - Please Confirm Diagnosis
 

I am turning my car into a Boxster Spec/BSR. I have started the car routinely during the process of removing weight. However, just recently, after I cut some wires that led to the amplifier, the car stopped turning over altogether. There is a slight tick near the front when I turn the key, but not much else. I believe the problem is the immobilizer but I want to check with the community to make sure I haven't missed anything. Following is what I have done so far.

I reconnected the wires I cut. This didn't change things.

I checked the battery. My multimeter registers about 12.5 volts. Nonetheless, I put it on a trickle charger for a couple days. Car still won't start.

I put the multimeter on the positive battery cable where it connects to the front of the car. It registers 12.5 volts.

I checked the clutch switch. It looks fine. I jumpered the wires. Still won't start.

I put the multimeter on the battery and watched it while I turned the key to see if there is any drop off. I have read that a significant drop off would indicate a problem with the starter and/or starter solenoid. There multimeter read roughly 12.5 volts every time I turned the key and changed very little.

I pulled the number 7 relay in the rear trunk and put a jumper wire between the two large wires. I turned the key and the car turned over but did not start. I have read that this indicates there is no problem in the battery-to-starter chain and, rather, that the problem is with the immobilizer and/or ECU.

I have not yet attached the multimeter to the solenoid or otherwise checked the starter. However, I understand these issues are ruled out by some of the other tests I did do.

In retrospect, I (stupidly) forgot to disconnect the battery before cutting the few wires mentioned above (to the amplifier). I wonder if this may have triggered something in the immobilizer? The immobilizer looks fine on the outside and inside, but I know these things are very sensitive.

Any thoughts or suggestions would be greatly appreciated.

IIRC there is an internal fuse in the immobiliser under the drivers seat.
Did you check it?

Yep. Checked that and it appeared to be good. I changed it anyway.

Ignition switch
 

I think you toasted your ignition switch, the only link between amp wires and the actual starting of the car would be the ignition switch, If I'm not mistaken when the inmobilizer is bad or not present the car would still crank but not start (maybe I'm wrong) but I would check the ignition switch, the contacts inside the switch are quite delicate and the little springs inside get burned easy with a short like cutting wires with the battery connected

Do the idiot lights light when you turn the key?

That would be great. I'll keep my fingers crossed when I check it.

The idiot lights are gone. Dash is completely out of the car.

I forgot to mention in my initial post that the key still activates the lock and unlock circuit. I'm not sure if this matters.

You had the car running without the instrument panel connected?

Good question. Yes, I started it several times with the dash out and at least one time about an hour before the problem.

Reconnect the instrument panel and see if the problem goes away. Someone recently discovered that the car senses there is no panel and refuses to start until it is reconnected.

If it does not, then my guess would also be related to the ignition switch.

I reconnected the instrument panel, but the car still doesn't turn over. All dash lights turn on when I turn the key.

A new ignition switch should be here tomorrow. I'll keep my fingers crossed. . .

With the immobilizer on my Audi (Bosch based as well), the starter would still crank the engine over, but the engine would fire for a few revolutions, basically a split second, and then it would die. The ECM woudl throw an immobilizer code.

I don't know how the Porsche immobilzer works but if its the same at the Audi and your engine won't crank, then the issue isn't with the immobilizer but with the starter circuit.

In any case, further diagnosis is a waste of time, and potentially harmful without having the factory wiring diagrams for reference.

What model year is and which engine has your Box?

Does it have the original ECU?

Which parts exactly did you throw out or cut?

Regards, Markus

Sorry, I should have mentioned that as well. The car is a 1997 with 2.5l engine. It does have the original ECU (as far as I know). I have been stripping the car for the track. So, dash, seats, interior, door trim and harnesses, steering wheel, airbags, heater, amp, radio, etc. have been taken out. I have not done anything to the exhaust yet.

^^^ Without backtracking, I suspect you are looking for the proverbial needle in the haystack..... ^^^