I am having a weird problem that i've not been able to find an explanation for.

Vehicle: 87 IROC -Z 350 tpi L98 block, power everything

The problem I am having is with my headlights, a fuse, and the starter. My dash, headlights, and taillights, are controlled by one 25 amp fuse.
The problem is, when that fuse is in place, my starter will activate just as soon as I turn on my headlights. The engine does not turn over (the fuel pump is not engaged) , but the starter will being spinning automatically (whether the engine is already running or not). When I remove this fuse, the problem is essentially alleviated.

Looking at the starter, and tracing the wires through the engine bay, I do not see anything that might have fused along the way or shorted out.

Has anyone else had this problem before, and/or does anyone have any suggestions on where else I might begin searching for this problem ?

Any ideas welcome

 

Check to see if you might have short at the Park/neutral switch and the light in the shifter.

 

First: This did not just start happening did it? I mean you didn't just go out to your car one day and turn on the lights and the starter started spinning? What work was done prior to this happening?
Somehow you are getting power to the solenoid on the starter thru the lighting circuit, bypassing the key!
Will this happen with the key turned off and just turn on the headlights?
Does it happen with just the running/parking lights on and no headlights?



Second: "starter spinning but engine not turning over". If this is the case, the bendix is also bad, because first the solenoid engages or pushes the bendix into the flywheel then the contacts are made in the solenoid to spin the starter motor.

The bendix or starter drive gear should only turn one way and not the other, if this goes bad then the bendix can be engaged to the flywheel but will not turn over the engine.

 

The last major "maintenance/modification" done to the car was the rebuild of my pull down motor for the rear hatch. This started happening one day while I was in the middle of that rebuild.

This will happen with or without key in the ignition. I don't think the car turns over though because the fuel pump is not engaging. I've a very audible holley fuel pump that makes its presence known when trying to start the car, but it does not engage when this happens.
Also If I try to start the car using the headlight switch (never thought i'd find myself saying that), it will just keep cranking until the battery dies. I can however, turn on the ignition right after attempting and start the car with no problems.

 

Can you expand on your thoughts behind the Park/neutral switch? I have a B&M Ratchet shifter if that makes any difference. Do you thnk that this has shorted somehow? Also, is the shifter light bulb (in the shifter) wired to the same fuse ?

 

I mentioned this since you said the problem occurs when you turn the head lights on and that shiftlight is the only thing in that area that gets power when you pull the light switch. You might have accidently grounded out the shifter to that light. Just a thought!!!!!!!!!!

 

"This will happen with or without key in the ignition. I don't think the car turns over though because the fuel pump is not engaging"

Can you lift the hood and see if in fact the engine is turning over with the headlight switch on?

 

Alright gents, I will try your suggestions and post the results tomorrow.. Thanks for all of your ideas and help thus far.

 

Can you please clarify 'turning over'

I can read that two ways

1) the starter spins, but does not engage the engine?

2) The engine is turning over (ie cranking) but not starting because the fuel pump isn't coming on

Things to Check and make sure of

1) that the wires on the big terminal of the starter aren't loose

2) that the wires on the big terminal aren't touching the wires on the little terminal

3) Make sure the wires on the big terminal aren't touching the braided wire connection the solenoid to the starter.

Don't forget to have fun and always check your grounds!

-jason

 

Perhaps I should clarify...

The starter cranks the engine as it normally would when starting the car normally. The fuel pump is not engaged however, so the engine does not start.

 

this doesn't help your situation exactly but i had several instances where the relay i used with the megashifter failed and left me stranded which is why i sold it..

 

You need to get a wiring diagram, find the wire that goes to the starter solenoid from the ignition key, does it go thru anything on its way to the starter solenoid?
Power is coming from the headlight circuit and powering that wire to the start solenoid somehow either by bare wires touching each other or through a common connection that should be insulated. Example would be a switch where both wires connect to it but normally are insulated from each other somehow they are now connected.
Find the large connector on the steering column and disconnect it, with the wiring diagram you should be able to determine wire color for the ignition key to starter, with the connector disconnected and the headlight switch on does starter engage? If yes then its not in the steering column, if no then something in the column up towards the ignition key is bad.
Question: does there happen to be a light on the column that illuminates the ignition key hole when lights are on? That could be a source of power. Start disconnecting things until the problem goes away, use the wiring diagram to help you decide what to try.

 

Alright gents, took a while, but me and a buddy made some significant progress tonight, after pulling the gauge cluster and pully the assembly for headlight switch, we found that the problem is in one of the connections. Their is a brown wire that seems to control the tail light assembly. When jumpered from the red (hot), it starts the ignition. This occurs whether that fuse is plugged in or not.

It should also be noted that even with the tail light harness disconnected, this occurs. What else does this brown wire control ?