I have been chasing an interrmittent electrical problem and don,t know what else to do. After starting truck,then turning the key off,it will continue to run. If the truck didn't start then it will continue cranking until I pull the battery cable. There have been times that it was started and driven and when I shut it down and go check, the lead from the positive side of solenoid to wiring harness ( which looks to branch into alternator ) has gotten overheated and melted the insulator off. I have replaced the solenoid a few times and the ignition switch trying to eliminate problems. The ignition module is less than a year old. I can't find any shorts and replaced any cables that were questionable. It's a 390 in a 74 f100. ANY SUGGESTIONS ABOUT WHAT ELSE TO CHECK?

 

also, it starts without depressing the clutch. but that really doesn't address the starting system being energized. what about an interrupter switch between the solenoid and starter? or should it be installed before the solenoid and after the ignition? At this point i'm not as concerned why but how to get around this issue.

 

When the truck continues to run with the key OFF - does it run like it normally runs, or does it kick around and hiss (dieseling)? How do you shut it off when this happens?

How is the main power feed to your truck smoking off the insulation without dropping a fusible link? Do you not have one coming off the solenoid - AKA has your wiring been modified somehow?

 

Truck wouldn't start and by accident the link was bumped during a jump start and it started right up. Replaced link with a section of 16 guage wire. I now have an issue with the solenoid freezing closed after starting and shutting it off. I have to pull positive cable to turn it off.

 

As far as starting with the clutch NOT pushed in, it does NOT have a "clutch pushed in" safety device like most new cars and trucks today.......

Hang in there the local FTE wiring/elec guru (fmc400) willl get the wiring issue straightened out I'm sure.

 

OK - so it's running with the key OFF, and you have to pull the positive cable off to make it shut off? Does it stay off once you reconnect the cable?

I can tell you right now that replacing the fusible link with a length of 16-gauge wire is UNSAFE and will not work. This is why you're cooking the insulation - that info would have been helpful to know right away. There are two problems:

(1) 16-gauge wire simply will not handle the current capacity of the truck's entire electrical system.

(2) The ONLY thing you should use to replace a fusible link is ANOTHER FUSIBLE LINK. I cannot drive this point home enough and for some reason it happens here all the time. The size of the link always needs to be 2 sizes below the circuit it protects - so if you're protecting 10-gauge wire, you would use a 14-gauge link.

Fix that FIRST before moving on to the rest of the problem. Doctors won't take you in for surgery if you have a major infection; trucks aren't any different!

 

I called "uncle" and replaced the wiring harness with one from the boneyard. The po was pretty good at hiding fire damage, and since replacing it, I have had no problems. I only wish I had tore into the harness deeper before beating my face on the fender over all these issues I have been having.