I mostly lurk here, but hoping someone else has run into this before and found a bug that's eluding me. 1988 F-250 4x4, 5.0, 5 speed.

The solenoid sticks from time to time. The engine starts but the starter will remain engaged. Turn the key off, key out of the ignition and it continues to drive the engine. The only way to stop it is to quickly remove the battery cable or rap the solenoid until it unsticks. Even removing the red/blue wire from the solenoid does not disengage it.

I found a bare spot where the red/blue wire appeared to be rubbing and coated the thin insulation with liquid tape, cleaned out corrosion from the first main connector in the drivers fender well where the red/blue wire terminate and applied some dielectric grease.

On top of this, I have a very good friend who is a Master ASE certified mechanic in everything but collision and school bus repair. He travels the entire USA and into Canada to train technicians. Flown in by wealthy people, and companies to fix their 'alligator' cars from Bently's, Ferraris, and Lambo's to heavy diesels. Last one was a Ventador in the dealer couldn't fix throttle body codes on (it has 4). He found a shorted wire in the engine cradle setting the codes. The guy is sharp.

We had a 4 channel PICO scope/laptop hooked to it and checked draw, amperage, etc. on every wire associated with the battery, solenoid, starting system. Everything tested very healthy and strong. And of course in typical fashion, it never malfunctioned while he was with it.

It has the original black cable running to the starter and an aftermarket positive battery cable he suggested replacing with a known new top shelf unit. Previous owner replaced the keyed ignition and obviously was throwing parts at it judging by the box that came with it.

So, I need some ideas. Even if it did act up when my buddy was hooked to it, it will burn the starter up in 60-90 seconds hoping he is scoping the correct wire that may be causing this and see the malfunction.

Anyone else dealt with this or have suggestion. My next step is to buy an OEM solenoid from the dealer.

TIA

Todd

 

Small update. Took my positive battery cable off and to an automotive electrical supply shop for a custom made cable. They used a heavier cable than what I had and top shelf copper ends soldered and heat shrinked.

When he used my old one to get length, he checked the terminal ends - and the end that bolts to the solenoid was VERY loose. You could wiggle it back and forth and feel clicking inside the end. Looking at it, it looks fine. Wiggling and it reared it ugly head. It was the type you'd buy off a rack at advanced auto/auto zone, etc. There was no solder involved in making this cable.

So, on went the new cable and immediately there was a difference in how easily the truck started. It didn't start hard before, but it turns a few times less before it sparks now.

Bad news, the solenoid stuck since the new cable went on. Going to put another solenoid on it assuming the one that is on there has internal heat/arc damage. Will do a search for a heavier duty solenoid than factory. Will report back with what I find.

 

Classic relay failure; no need to overthink it so much. If the contact circuit remains closed when you remove the wire to the coil circuit, and opens with a physical blow, the relay is shot. Shouldn't require anything special; if it's original, no surprise it's failing at almost 30 years old. But if you want something heavy duty, consider something like a Stancor 586-902. You'll have to ground one terminal of the coil circuit, since, like most "heavier duty" generic relays, the mounting base does not ground.

 

Thanks for listing the heavier duty part for me madpogue. I knew the solenoid was failing, but what is causing it to fail. PO had put a new one on, I'd replaced it within the past few months and that one began to fail. The contact the cable had in the solenoid end was horrible. Likely causing heat and excessive draw when marginal contact was made. Hit and miss?

Going to get one of the solenoids you recommended. Thanks again!

 

My 89 had this exact problem. Aftermarket solenoid was the problem. They have 4 posts when there should only be 3 posts. Got a good solenoid on there and it's worked ever since (2 years ago)

 

ever since starter relay manufacture has been shipped to china, the quality has gone into the garbage can. i have had to replace numerous brand new relays that do not work out of the box. even when bought directly from ford.

i have since started to switch to the stancor relay on all my vehicles.