1987 F-250 starter sticks

Periodically while starting my truck, the starter will not stop cranking, even if the key is off and out of the ignition. The only thing that will make it quit it to bang on the starter relay with a hard object. The starter and ignition switch have both been replaced. The starter relay has been replaced with different brands multiple times. The wiring from the ignition switch to the relay to the starter has all been inspected and deemed okay by my mechanic. He cannot figure out what is wrong and has been working on the truck for 5 months. p.s. - 1987 Ford F-250 w/460 ci engine.

Is the starter relay still recieving a singal to stay energized or is it doing it all on its own?

I believe it’s still receiving power from the ignition. This, I think, is why he replaced the ignition switch (which did not fix the problem). He wants, as a last resort, to install a separate solenoid by the relay that will physically stop power from reaching the starter relay once the key is turned off. I am hesitant since the truck was not originally manufactured with a separate solenoid. I do not want a cobnobbeled truck.

Hitting the starter relay works because they are all defective. They’re not all bad but good ones are getting rare. Try to find them made by Sorensen. The other way would be to buy one from the boat parts rack. They look tougher, being made with steel and all. To me, the plastic ones are all crap.

My mechanic has tried 6, yes six, different relays at this point, including a heavy-duty relay with a steel case. None have worked. He blamed China and installed a Motorcraft o.e. which still does not work.

The body has to have a good ground for the relay to work properly.

You are either missing a tooth on the flywheel, or the starter remains engaged with the flywheel after you stop ignition.
What most likely is happening is that the starter motor gear is getting stuck in the extended position that engages the gear to the flywheel. Most likely the problem is with the starter and not the flywheel. But it works both ways. Your starter motor gear can get stuck if the flywheel is missing a gear, just because there is not enough pressure to retract the gear once it is a little dislodged on the flywheel.
I’d remove and inspect and bench test the starter first. If it’s okay, you probably need to replace the flywheel.

The starter was replaced about 2 months ago. The flywheel was replaced about 2 years ago. I have put probably 1000 miles on the truck since then. I would find it hard to believe that a flywheel would wear out in that amount of time.

Flywheel teeth don’t wear as much as they break. But you have replaced the flywheel two years ago so that can’t possibly be the problem.
Your starter motor is not disengaging. Try this: after the car starts, turn the engine off. Does the starter keep trying to turn the engine over?

Before the wiring is removed from the steering column and replaced, there may be something worth doing. Find the ground from engine to body. It will be connected to the firewall. If it is missing or broken or the body end has never been cleaned with a wire brush or scraper, you could get a condition that is worsening the short circuit that you may have.

Clean that ground and change the negative battery cable and work from there if the problem does not just go away. Bad grounds can cause strange things to happen.

Yes, the starter continues to crank regardless of key position. The key can be on, off, or completely taken out of the ignition and the starter will still continue to crank away. Of course if the key is kept at the “on” position, the engine will turn over, and the starter will still be cranking. If the key is turned to the “off” position, or taken out completely and thrown in the bushes, the engine will not turn over, but the starter will continue to crank away. Besides the starter and flywheel being replaced, the ignition switch has been replaced once, and the starter solenoid relay on the inside of the pass. side fender has been replaced 6 times with different brands, and still the starter continues to crank.

The starter may not be mounting squarely to the flywheel. If the bendix gear becomes bound into mesh with the flywheel it will hold the solenoid contacts closed, turning the starter.

I had the same problem w/ an ?87 F150. When you turn the key on the steering column to the start position, you move a shaft that is engaged into a heavyduty spring loaded starter switch that is mounted about knee level to the steering column. When all is working fine, you turn the key to the start position and the shaft moves the spring loaded starter switch mounted to the steering column to apply 12V to the starter, the starter engages, you release the key, and the spring loaded switch releases from the start position and returns to the run position. The shaft that runs from the key switch is about a 3/8 inch diameter shaft w/ a short 90 degree bend at the end about 3/8 of an inch long. This 90 degree section is what engages the heavy duty ignition switch. The spring loaded switch is worn where the 3/8 inch long section enters the switch. So when you release the key from the start position, the shaft has jammed the starter switch to the start position. To find the starter switch you must lower the steering column. I think you need to remove a vinyl or plastic cover from around the steering column near the dashboard. Then you?ll see 2 bolts & probably a metal collar holding the steering column up. Remove the bolts & the steering column will drop to the seat. Then you?ll see the starter switch mounted to the steering column w/ 2 bolts. Remove the bolts leaving the switch connected. It will now be hanging down near your knee (put the steering column back up to get it out of your way). Now, turn your key to the ON position. Then, using a screwdriver, push the starter switch forward to the start position. The truck should start, release the switch, & you?re in business. You can start your truck this way or buy a replacement switch. My replacement switch failed within a year or two, so I let the 2nd failed switch hang down & used the screwdriver method to start the truck. To access the starter switch will take about 30 minutes to 1 hr.