engine only runs when ignition switch turned backward (2 Viewers)

[Red Panda Roll]

I've seen quite a few threads about starter problems similar to what is going on with my '76, but not quite. When I turn the key to "start" it cranks fine and sounds like it's running but as soon as I release the key to the "on" position the engine dies.

Same thing happens with the ignition switch being activated by a screwdriver (as the steering column cover is removed).

Here's the weird part: When turning the ignition switch backwards (beyond the "off" position -- 1 click counterclockwise) the engine starts itself and stays running (though I think the starter is staying engaged because it's a little noisy over there). I suspect there's something inside the ignition switch that's wacky or loose.

I traced all the wires today and just can't seem to figure out what the HECK is going on with this thing. There is some PO nonsense going on with the wiring e.g. there's a 10 g (or so) black wire running from the "B" post on the alternator to the "AM" on the ignition switch. (Just now I can't recall where the factory white/blue one from the "B" post goes but I have continuity at the regulator as I should.)

Anyway, has anyone heard of this happening before? I'm so confused by these electrical shenanigans.

 

[handcannon]

I've seen that happen before. It took me several days to figure out why my friends car wouldn't stay running, just like your 40. The description that follows is a very simplified version of what the ignition system actually is.

I'm assuming you have a points system in your distributor. There is a resistor to lower 12V down to around 6 to 9V to keep the points from being damaged by full 12V going to them. When the starter is being used the starter solenoid bypasses the resistor and sends full 12V to the distributor to make starting easier. Then when the starter is no longer energised for starting that 12V that bypasses the resistor is stopped.

What's happening is that a full 12V from the starter is allowing the motor to start. But, when the key is released from the start position that 12V bypass from the starter is no longer going to the distributor. Then, the lower voltage that should be coming from the resistor and going to the distributor is not there, which then allows the motor to die.

Somewhere, somehow, the circuit that should be sending a reduced voltage to the distributor is not doing that. There are a number of things that could stop the lower voltage that should be going to the distributor. It could be the ignition switch, the resistor, or the wiring from the key to the resistor,or the wiring from the resistor to the distributor.

Don

 

[Chris Wilcox]

I think you should take your ignition switch apart to see if the thin brass piece is worn through. Mine was worn through and therefore the ON position didn't have contact. You could just move the key to on and check for voltage through the harness where it should be too to check things out.

 

[Red Panda Roll]

I've seen that happen before. It took me several days to figure out why my friends car wouldn't stay running, just like your 40. The description that follows is a very simplified version of what the ignition system actually is.

That's encouraging.

I'm assuming you have a points system in your distributor.

Yes. Points looked good (i.e. not fried or pitted, etc.) a few days ago when I RE-checked and Re-gapped them to .457 mm (.017")--if memory serves me. That helped a lot as I had let it slip to a far too large gap when setting them the first time. Ooops.

There is a resistor to lower 12V down to around 6 to 9V to keep the points from being damaged by full 12V going to them.

Is that the "ballast" that sits on top of the ignition coil?

When the starter is being used the starter solenoid bypasses the resistor and sends full 12V to the distributor to make starting easier. Then when the starter is no longer energised for starting that 12V that bypasses the resistor is stopped.

What's happening is that a full 12V from the starter is allowing the motor to start. But, when the key is released from the start position that 12V bypass from the starter is no longer going to the distributor. Then, the lower voltage that should be coming from the resistor and going to the distributor is not there, which then allows the motor to die.

Okay.

Somewhere, somehow, the circuit that should be sending a reduced voltage to the distributor is not doing that. There are a number of things that could stop the lower voltage that should be going to the distributor. It could be the ignition switch, the resistor, or the wiring from the key to the resistor,or the wiring from the resistor to the distributor.

Okay. I've got more homework to do, I think. Thank you, Don.

 

[Red Panda Roll]

I think you should take your ignition switch apart to see if the thin brass piece is worn through. Mine was worn through and therefore the ON position didn't have contact. You could just move the key to on and check for voltage through the harness where it should be too to check things out.

OOH! Occam's Razor is a beautiful thing. I will definitely check this when I get home. I did order a new ignition switch the other day, too, so if this is the problem I'm covered. Thank you.

 

[handcannon]

Is that the "ballast" that sits on top of the ignition coil?
Okay. I've got more homework to do, I think. Thank you, Don.

Generally the ballast resistor is in very close proximity to the coil. And, yes, it is a white ceramic body.

A multimeter will be your friend when you start chasing down where the problem is. You can start with a 12V probe light, but it will just tell you if you have voltage, not what the voltage is. Start with turning the key on and see if you have 12V going into and 6 to 9 volts out of the resistor. This will tell you if you need to look upstream or downstream of the resistor.

Don

 

[Red Panda Roll]

Great. That sounds pretty straight forward. I'll post once I've had a chance to do that.

 

[Red Panda Roll]

OOH! Occam's Razor is a beautiful thing. I will definitely check this when I get home. I did order a new ignition switch the other day, too, so if this is the problem I'm covered. Thank you.

Okay. I checked (and broke the house in the process of disassembly) the switch and noticed nothing out of the ordinary. I replaced the whole shebang last night with a new one from CCOT and it does the same thing. So I guess I need to go down the rabbit hole of current and follow @handcannon 's advice. I'll update when I know something . . . anything.

 

[Red Panda Roll]

@handcannon I turned the key to "ON" (engine not running) and, using my multi-meter, don't get any voltage whatsoever at the ballast resistor. I assume now that the problem is "upstream" toward the ignition switch, yes?

I'm not sure where to start, though. I have a printout of the wiring diagram. Is it the "IG" wire from the ignition switch I should chase? It's supposed to be a black/yellow wire that goes to the fuse panel then leads to the igniter.

Any further leads or links would be appreciated.

 

[Red Panda Roll]

PROBLEM SOLVED!!!

Thanks to @bsmith123 on this thread: Help! Won't Stay Running !

I cut an 8" piece of 10 gauge wire, put a ring connector on one end attached that to the + terminal on the coil. I tucked the other end in between the + terminal and its wire on the battery and the truck runs when in the "ON" position now!!

• 

I'm so stoked!

Looks like I need to order a new ballast bypass resistor tonight.

 

[Chris Wilcox]

Sweet.
Having a new ignition switch isn't a bad thing either. They do wear out.

 

[Red Panda Roll]

I replaced the ballast bypass resistor last night and it did not fix the problem. GRRR!!

I think the creative wiring a PO did might be the problem.

Any thoughts on this?