Engine won't fire - starter solenoid issue?

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sz3gfj
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Engine won't fire - starter solenoid issue?

Postby sz3gfj » Thu Jun 16, 2022 9:11 am

66 toronado. Starter turns but engine won't fire. Replaced coil and points, then found out points are always grounded... even when open.
Looked for grounds. With the key off, the lead connected to the coil + is grpunded.

Per the 66 Toronado wiring diagram, this lead has two branches. The first comes from the ignition switch I terminal. With the key in the off position, this lead should not be grounded. The second branch comes from the starter solenoid R terminal, and is spliced with the ignition switch lead somewhere in the harness. I think, to work properly, this lead should not be grounded.

So, I'm thinking my issue may be because of an internal short in the starter solenoid which grounds the R terminal to the case, or due to a break in the lead which grounds to the vehicle. I'm not yet able to get under the vehicle to remove the leads from the starter solenoid to test either configuration for grounding. Also, I don't know how a short from the R terminal of the solenoid to ground would manifest itself. I believe the voltage to the R terminal is provided through the starter feed once the solenoid is activated; since the starter feed is the largest current draw, I don't know how this short would affect things. The engine appears to crank without a noticeable affect to the starter.

Anyone else seen this? Can anyone provide guidance?

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Otto Skorzeny
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Re: Engine won't fire - starter solenoid issue?

Postby Otto Skorzeny » Thu Jun 16, 2022 2:02 pm

I'm not sure I followed everything but make sure the negative wire from the coil goes to the distributor.

Make sure the condenser is hooked up properly. They're all crap right out of the box today so if you have one that was on the car when you last saw it run, re-install it.

Do the plugs get any spark at all?

sz3gfj
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Re: Engine won't fire - starter solenoid issue?

Postby sz3gfj » Fri Jun 17, 2022 11:35 am

Found the problem... dead short somewhere in backup light circuit.
Removed the backup light fuse, and the car was able to start.

Now all I have to do is find out where the backup light circuit is shorted... somewhere past the fuse block. (I suspect that either there is chafing which cut through the insulation, or the critters may have gotten to it... even though I try to keep them out of the car!) I will need to trace the wiring from the backup lights to the fuse block to find the short.

BTW, the wiring diagram I got from classiccarwiring.com was invaluable in helping me find this issue.

Thanks to all for your help and suggestions.

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Otto Skorzeny
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Re: Engine won't fire - starter solenoid issue?

Postby Otto Skorzeny » Fri Jun 17, 2022 2:05 pm

That's pretty cool that you found it. Something completely unrelated to the ignition might have taken a lot longer to pin down.

sz3gfj
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Re: Engine won't fire - starter solenoid issue?

Postby sz3gfj » Sat Jun 18, 2022 3:20 pm

Did further investigation and found source of problem was the left backup light bulb socket, which had corroded so that the center contact had shorted to the outer case. Quick fix was to remove the center contact which removed the short. This destroyed the socket and left me with one working backup light (which is better than none). Looks like I’ll need to remove the rear bumper to remove the backup light housing, to see if I can remove the bulb socket. Not sure I can find a replacement socket. I expect that a used LH backup lamp housing with a good socket might be unobtanium. So, any ideas on how to fix would be helpful.

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Otto Skorzeny
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Re: Engine won't fire - starter solenoid issue?

Postby Otto Skorzeny » Sun Jun 19, 2022 6:00 am

John Dorcey probably has a backup light housing.

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roland
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1970 Ford LTD Country Squire 429
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Re: Engine won't fire - starter solenoid issue?

Postby roland » Sun Jun 19, 2022 11:37 pm

John Dorsey sold me a complete rear wire harness with good sockets. Real plug and play. No more frustration to the rear lights. He has a lot of cars...
Roland TOA#860


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