Urgent Question: starter / ignition wiring

[flashgordon64]

I have a 86 911 turbo and we(engine builder and I) need a starter signal wire to "excite" the starter to make it engage. We can't seem to find anything in fuse panel where there is a hot wire key start only. Everything is either hot all the time or hot key on. Nothing hot key "start". From looking at the factory wiring diagrams it appears it comes off of the ignition switch and is then sent to starter via DMI box, all of which(factory electronics under seat and engine bay), have been removed/cut out of the car when we converted to EFI conversion. All wires on the back of ignition switch are same way; "hot key on." Only nothing hot when the key is in the start posotion. The only way we see to do it is with a starter button. We would like to avoid that if possible. Any ideas?

*I don't know if this helps or not. There is an aftermarket alarm installed in the car*

Mitch

[Daniel930]

You should have a yellow wire from the ignition switch back to your 14 pin connector, then into the engine wire harness to your starter.

[flashgordon64]

That's the problem. In our haste to create a custom chassis harness the yellow wire somehow disappeared, which brings me back to the original question

[T77911S]

well, there HAS to be a "hot in start" on the ign sw or it never would have started from the factory. i cant read the drawing that well, looks like pin 50 on the ign sw. (maybe 56).
it may split off and go somewhere else, but it goes directly to the starter thru the 14 pin connector.
pin 30 is the main pwr in. if you have power, use a test light to find the start signal.

[nocarrier]

I believe the yellow starter wire is also used to supply the ground for the A/C relay in the smugglers box. It's designed so that when the ignition switch isn't in the crank position the a/c relay is getting its ground through the coil in the solenoid. When you turn the key to the crank position the yellow wire becomes hot with +12 volts energizing the starter solenoid. At the same time what was once ground for the a/c relay is now +12 volts so the relay disconnects and turns off the a/c to help facilitate cranking. As soon as you stop cranking, the yellow wire returns to ground through the starter solenoid's winding and the a/c turns back on.

Hopefully this helps you with your starter circuit.

[T77911S]

yea, it does something funky like that, dont remember for sure. i will never understand why porsche did something like that.

[Daniel930]

I did a custom wire harness, this is something I bought from DC, it's for a 86+ turbo, I was going to put it on the BB for sale, if you need it $150.00 shipped.

Question: how far did you cut the yellow wire, obvious it runs down the center of the car in the main wire harness.

[flashgordon64]

Originally Posted by Daniel930

I did a custom wire harness, this is something I bought from DC, it's for a 86+ turbo, I was going to put it on the BB for sale, if you need it $150.00 shipped.

Question: how far did you cut the yellow wire, obvious it runs down the center of the car in the main wire harness.

Thanks Dan, I will let you know. I need to try out some of the suggestions the guys recommended.

Another thing of note. When I bought the car from the PO I sent the car off to a local stereo shop to sort out some of the wiring issues before. There is a G50 conversion wherein they bypassed the clutch switch. There was also several alarm systems where they never removed the old wiring but added the new systems over the old. So it's a bit of a hornets nest(winter project) going on under there

[T77911S]

alarms are the work of the devil.
most involve cutting the already stressed yellow wire that runs from the front of the car back to the back then 1/4 way back to the front. add in some cheap A$$ crimp connectors going to the relay that is put in there to lock out the start signal and things get REALLY bad.