911SC Ignition Problem - Power but no start

[aforestoftrees]

Hi all,

I replaced my entire ignition yesterday (both mechanical and electrical portions) with a brand new unit. After installing, everything worked and the car started.

Today, the car won’t start. When I turn the key, I get power and accessories come on, but turning all the way doesn’t do anything to start the car (nothing tries to turn over). There is also no resistance on the last portion of the key turn (no spring return or any other feeling). All of the electrical connections seem well seated and secure.

I’ve read many posts about ignitions, but all the issues seem to be related to worn or broken parts, which doesn’t seem applicable here since it is brand new.

Any thoughts on what I could try? This is for a 1979 911SC.

Thank you,
Rich

[Schulisco]

Do I get it right that the starter motor doesn't crank the engine?
Starter motor also does not engage?
Then the ignition is not be the culprit. Could be a stupid coincidence that either the lock or the the starter motor went bad over night...check if the power from the lock goes to the starter motor.

Thomas

[aforestoftrees]

You are correct - the starter doesn’t do anything. There is no change from moving the key from the “accessory/on” position to the “start/run” position (no resistance, no extra car noises).

How would I check if the power goes from the ignition to the starter motor? I’ve only had this car a few months and am learning how they work.

Thanks,
Rich

[Schulisco]

There are several "no crank" threads here:
https://forums.pelicanparts.com/search.php?searchid=25609023
Do you know how to read electrical car wiring diagrams?

The basic starter wiring afaik does not differ that much from year to year on the SCs...

https://classickabelboomcompany.com/wiring-diagram-porsche/

Thomas

[aforestoftrees]

Thank you, I’ll look through those threads. Unfortunately, I don’t know much about electrical or wiring but will see what I can learn about reading the diagram. Thank you again.

Best,
Rich

[wazzz]

I find it weird that you feel no resistance or spring return force when turning the key from "accessories" to "start" then back. Your problem may lie in this area.

You may also want to check if power (+12V) is present on the yellow wire exiting ignition switch when you turn the key to start".

[Walter_Middie]

Sounds like the mechanical and the electrical portions of the ignition switch have become disconnected.

which doesn’t seem applicable here since it is brand new.

NEW is an acronym for Never Ever Works.

[Dpmulvan]

It’s probably the new switch, I wonder if they’re made in China??