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running when key is off

blue65coupe

Well-Known Member
Not mustang but general is full of stuff. Info:

1976 f250 with 460 carbed, stock engine setup recently "freshened" with all new gaskets, plugs, etc. The truck continues to run when key is off. Pulling a battery cable does nothing but 3 or 4 good revs of the engine will shut the vehicle off. Given the truck will shut off with some good revs I am tentatively ruling out the ignition switch/solenoid. Possible timing but truck runs/idles great. Potential carb/vacuum issue allowing too much air in. Whatcha think before I dig into it tomorrow?
 
Not mustang but general is full of stuff. Info:

1976 f250 with 460 carbed, stock engine setup recently "freshened" with all new gaskets, plugs, etc. The truck continues to run when key is off. Pulling a battery cable does nothing but 3 or 4 good revs of the engine will shut the vehicle off. Given the truck will shut off with some good revs I am tentatively ruling out the ignition switch/solenoid. Possible timing but truck runs/idles great. Potential carb/vacuum issue allowing too much air in. Whatcha think before I dig into it tomorrow?
My cause for doing the same thing on my '70 was a bad ignition switch. Don't know if that helps.
 
If it's still running, it's getting spark from somewhere right? Ignition switch or solenoid is bad.
 
Incredible high compression and it is self igniting like a diesel? Ok probably not! I would guess the timing is off.
 
What temp is she running at idle? This could tell you if it is ignition related or timing.

The stock gauges will not tell you.

If your timing is off it will run hot causing this.

Mel

Sent from my XT1030 using Tapatalk
 
If she runs great .....my guess is also the ignition switch.
After you turn off the ignition , do you still have some voltage on the (+) pole of the solenoid ?
If so , ignition switch or cable that has a short circuit with another one that also is hot when the ignition is on.
Does this car have a resistor wire or just a resistor in its ignition circuit ?
 
Thanks, going to check timing today but my initial thought is timing is good. We'll see. Will hit the ignition switch first since that is the general consensus of this group of braniacs. Wait a minute...........am I really taking Dale and Mark's advice? I'm screwed. Might as well rebuild the carb. Will keep you posted.
 
Not timing issue, haven't checked switch. Engine running today, key off, disconnected both battery cables and purred like a kitten. Grounded out the positive cable and she cut off.
 
Update: Replaced ignition switch, didn't work. Replaced ECM, didn't work. Testing wires I unplugged the harness from the back of the switch. I have two hot wires instead of one. Gotta find out what's crossing pwr and why.
 
Update 2: Decided to try solenoid. Hooked new one up and damn truck literally tried to crank...wth? Unhooked, hooked old solenoid back up and guess what? Truck starts and shuts off like it should. So, truck wouldn't shut off and after trying the switch, ecm, solenoid, and going back to all original parts.............truck is operating as it should. Who knows.
 
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