Starter does not try to engage, but ignition switch turns normally?!?

[BottleNose]

Hi all,

I've got a strange problem with my '70 911S Targa...the key turns in the ignition and all lights come on just fine, but when I turn the key further to engage the starter, nothing happens. The lights stay bright and don't dim like they usually do as the starter draws hard on the battery. Somehow the starter is not getting "the signal" to operate. Battery tests good for voltage and amps. Thought it might be the ignition switch, but I unplugged the connector in the back and hooked up a known good ignition switch and I have the same problem.

What should I try next? Any help is appreciated.

[rnln]

there are a lot of thread about this. Mostly, the starter signal wire (yellow) from the ignition key to the starter solenoid. This is one of the related thread. When it happen, try to get down and measure this wire at the stater while someone starting the car, to see if the wire get enouh voltage at the starter solenoid.
Becareful down there when someone start the car. Please note that you do it at your own risk.
Anyone replaced the starter yellow/signal wire? Please help.

[ossiblue]

Originally Posted by rnln

there are a lot of thread about this. Mostly, the starter signal wire (yellow) from the ignition key to the starter solenoid. This is one of the related thread. When it happen, try to get down and measure this wire at the stater while someone starting the car, to see if the wire get enouh voltage at the starter solenoid.Becareful down there when someone start the car. Please note that you do it at your own risk.
Anyone replaced the starter yellow/signal wire? Please help.

+1. Be sure to disconnect the yellow wire from the solenoid to run the test for voltage otherwise you will be reading the voltage drop as the solenoid/starter draw current. If the yellow wire checks out with proper voltage, then it is possible the problem is in the solenoid/starter.

[BottleNose]

OK..finally got around to checking the yellow wire this weekend. I disconnected the yellow wire at the starter, and there is ZERO voltage coming from that wire when turning the key to start. However, I measured 12V at the yellow wire coming out of the ignition switch (#50) when turning the key to start. So something is interrupting the current flow between the ignition switch and starter solenoid.

I did notice some weird things near the solenoid...there was a black wire just floating there unplugged. Also, at the solenoid the yellow wire has a spade splitter (so you could connect two wires to the one male spade on the solenoid), but no other wire was attached to it. I tried connecting the black wire to this but it made no difference.

This is all so strange since I haven't done anything to the car since I last drove it a month ago. What should I try next?

[ossiblue]

Look inside the trunk, behind the cardboard cover and under the cowel, for the wire loom as it comes through the bulkhead. My 73.5 has the yellow wire exiting the loom for a short distance and it has a connector. See if that is the case with your car. If it is, pull apart the yellow wire at the connector and test the part coming from the bulkhead while someone turns the key to start. If it tests good, jump a hot lead to the other part of the yellow wire--the part that goes back into the loom. Be sure the car is out of gear and the ignition is off. You should hear the starter turn over. If it doesn,'t then there is likely a problem along the wire.

[BottleNose]

Thanks for the help L.J. After I took the cardboard cover off the bulkhead I noticed an owner-added kill switch. Some kind of primitive security system? Somehow the switch went bad and interrupted the current flow. Easy fix!

Gotta love previous owners.

Thanks again all!

[rnln]

similar to my problem but instead of 0v, I got around 7.xxv on the yellow wire. My problem is intermediate so whenever it happen, I jump a 12v to this yellow wire and drive. No time to search for the exact problem location yet.
Good luck.