924Board.org

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

I'm working on bring a 1981 931 back to life. Eliza has been helping me a lot (thanks, Eliza!), but I'm not there yet. I replaced the starter recently, which involved replacing the wires where they were initially. Then a couple of weeks later it starting cranking by itself out of the blue. Eliza sent me some pics and guidance for how to wire it, but when I went to check my connections today, I realized the wires I have don't seem to match what Eliza sent me. Specifically, I have three wires to connect to the solenoid. One goes to the battery, one to the alternator (both of which attach on the large post) and one that goes to the ignition lock. Should there be another one? The engine had been completely rebuilt and and it has many swapped out parts, so is it possible I have the wrong wiring setup for the car? I've attached links to pictures for reference. The one with German is from Eliza, of course

. Thanks in advance for any help.

https://isu.box.com/s/a05uazrlglt7xq9ag6pe7ga9kfhqpofq
https://isu.box.com/s/sr7yjjb3pzf0zafb6jc1ksyzkugjmr7x

chuck21401 · Joined: 20 Feb 2005 Posts: 526 Location: Annapolis, MD

I have pictures around here somewhere. In the meantime, here is the wiring diagram for a 1980 924.

EDIT - This is the wrong diagram...the 1981 931 wiring is different...see other diagram posted below.

In addition to connecting the wires to the correct terminals....the wires or connectors cannot be touching.

re: Then a couple of weeks later it starting cranking by itself out of the blue.

That could be a problem. Especially if the car is in gear!

_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

Thanks for this, Chuck. I actually had the self-start thing happen with mine. Fortunately, it was not in gear. I have an additional question. I don't seem to have the black wire that connects to 15a in the diagram and eventually runs to the ignition coil. What would be the result of this? I'm getting pulsing voltage at the ignition coil for what's it's worth.

chuck21401 · Joined: 20 Feb 2005 Posts: 526 Location: Annapolis, MD

chuck21401 · Joined: 20 Feb 2005 Posts: 526 Location: Annapolis, MD

Here are two pictures showing how the wires are connected in my car.

The two thick wires are connected to the same post.
The red/black wire is connected to a post.
The yellow/black wire is obscured. That one is not easy to reconnect...tiny screw!

In this picture the red/black wire is disconnected so now you can see the black/yellow wire.

_________________
1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

Many thanks for this, Chuck. It clears up a lot. I have accumulated quite a few wiring diagrams by now and it seems they are inconsistent in respect to the 2 versus 3 wire setup. Now I know why. So it seems I don't need to worry about the additional wiring, especially since the starter is working as it should now. So I'm back to the beginning trying to figure out why it won't quite start and run.

Thanks again!

Brent

chuck21401 · Joined: 20 Feb 2005 Posts: 526 Location: Annapolis, MD

BWW · Joined: 21 Sep 2021 Posts: 58 Location: Idaho, USA

I do, Chuck. I will have a close look at these. I've also been following Vaughan's guide posted at the top of the page. Thanks for the suggestion.