Having a bit of a time with an electrical issue. I’m trying to systemically work this. Below are details and I am slowly going through tracing all wires. At this point I’m looking for insight into something I may have overlooked.

Details:
1975 1.8L / Web Carbs / Mallory Unilite

Issue:
No power when ignition is keyed on and car will not start.

How this event unfolded.
1. Car won’t start. Ran and started great night before but now it’s kaput.
2. Switched batteries suspected due to an Optima RedTOP being too far drained to adequately hold charge.
3. Replaced battery, car started.
4. BUT, When went to restart car ~15 minutes later. Won’t start AND no power for any electrics (Fuel pump, lights). Confirmed battery is charged.
5. Ensured battery was charged, still exhibits same issue. Cannot start and no power at all

Steps taken in attempt to remedy:
1. Replaced ignition switch (old one was cracked, but not horribly)’. New one was from pelican not OEM Porsche. Did not remedy.
a. Have attempted to start via ignition switch via screwdriver in case tumbler was too worn (same result)
2. Verified transmission ground strap was good (yes and it’s only 2 year old)
3. Verified 12V at ignition and at battery
4. Cleaned ground at seatbelt interlock relay
5. Tried to jump starter via a screwdriver across the poles but did not engage.
6. Starter worked when pulled and bench tested. So not enough voltage is getting to starter when in car?
7. Fuse 10, 11, 12 show 12V


Recent work done:
1. -New Clutch (verified transmission grounding strap connection). Drove great afterwards.
2. -Did seatbelt interlock relay bypass

Potential causalities leading up to event three weeks ago:
1. Son washed car and had would not start. Let dry overnight and started next day.
2. Momo horn ring was causing a short and had caused battery drain. Thought I had fixed and car ran without incident for 3 weeks or so until yesterday.

Many thanks in advance!

Change your battery cables.

Your getting 12v on the starter solenoid's yellow wire when the key is turned????

Do the oil pressure and gen lights come on when the key is turned to the first position?

Have not test that yet.

Have 12v at ignition wire (ignition switch steering column)

No lights whatsoever in position 1.

Not good enough. Need to know the exact voltage at the spade terminal when disconnected from the solenoid and the key is turned to start position.

.25v at the female spade terminal for solenoid when position 1 keyed.

Got the power to electrics back and THEN....Just got it to fire and start!!! I'm not sure I'm completely out of the woods yet as it had started before then stopped as noted beginning post.

I'm going to redo the interlock bypass connection.

Need to button all up and slowly go through. I'm not certain what exactly fixed root cause. Maybe the starter was not connected properly or is on the fritz. It fired after I reinstalled the starter - possible my connection was poor and did not realize it.

I did put a fresh new negative battery cable which had to have helped.

Possible problem at the relay plate?

I'm working though this myself now.

Got it running. Starts just fine now. Gotta see if it holds charge overnight, as I'm not totally confident yet.

Three things:

1-Ignition switch was cracked; it worked, but was indeed cracked
2-I suspect when I did the interlock seat bypass (connected two yellow wires together) I did not have a good connection.
3- New negative battery cable seems to have helped as well (touch wood)

Let me know your status as it would be useful data if the problem persists.

Cheers -
Greg

Clean the battery posts and the clamps that go on them. That sounded an awful lot like a bad battery connection as well.

--DD