Guys,

Here is my problem. I have an 87 2WD with a 351. The truck has the fender mounted solenoid for the starter. About three or four weeks ago, the truck would fail to start when the weather was HOT (90+). The key would turn all the way to the START position, but I would get no power to the starter. All of the dash lights lit but no ignition. There was no audible 'click' from the solenoid either.

My battery was about 4 years old, so I replaced it and bought a new solenoid from Ford. When I replaced the solenoid, the truck started normally. The second start attempt, the (I assume original) starter then would not disengage from the flywheel. I then replaced the starter with a new unit.

Now we have: new battery, new solenoid, new starter. With this combination, the next start attempt caused the starter to run hot (constantly). Removing the key from the ignition did not stop the starter. Removing the red energizing wire from the starter to the smallest solenoid post did not stop the starter. This leads me to believe the solenoid went bad and was always sending hot current to the starter (on this model it grounds at the bellhousing and has only the feed wire from the solenoid). I then bought another solenoid directly from Ford. Replaced this part and everything worked great for about 24 hours.

Last night when I left work, on the first crank the starter stayed running again, even with the key out of the ignition. Removing the engergizing wire (from the ignition) at the solenoid also did not disengage the starter. Only removing the positive battery connection stopped the starter. I had my original (heat-affected) solenoid, and replaced the new with the old. Voila, it cranked normally.

Any ideas on this? I believe that once the new battery and starter were in place, the solenoid has been my problem. I just find it hard to believe I could get two defective solenoids back-to-back from Ford.

I am now using the original solenoid in the truck and it is fine, but I'm worried that when it gets hot, the truck won't start again. Can solenoids be affected by heat conducted from the truck body (ground screws)?

Any help or ideas would be greatly appreciated.

B.Foley
Charlotte

 

No, ambient heat shouldn't be a problem for the solenoid, nor the starting relay. That's exactly what BOTH of them are, is relays. They have a coil and some contacts, and neither is used any longer than necessary to turn the engine over an crank it. After cranking, both should drop out.

As far as getting defective parts, it wouldn't be the first time, but two back to back is stretching it.

It sounds to me as if something is welding the contacts in the starter solenoid (the one ON the starter). The fender mounted unit does little more than provide the power signal to pick up the main solenoid on the starter, and send a crank signal to the ECM. When you release the key from the START position, that relay on the fender should drop out, and the starter should stop. I presume you were talking about the small wire going to the solenoid on the starter? If you removed that (it's now bolted on connection, so how'd you do that?) then the contacts in the solenoid are welding together. If you're talking about the small wire coming from the keyswitch to the starter relay on the fender, once you release the key, it has no power on it anyway. When you disconnected the smaller wires, did you see any arcing like you were dropping out a load? If not, you probably weren't. As far as disconnecting the battery cable while the starter's running, you're a very brave man. Ever seen a battery explode? I have, it wasn't pretty.

 

My 87 has no solenoid on the starter itself and the crank signal to the computer comes from the ignition switch...

How would you suggest making the starter stop without disconnecting the battery?

I had trouble with the Ford solenoid sticking (I could hit the fender and get it to release), so I bought a replacement from NAPA. It has a sticker on it that says "diode supressed". If somehow the battery + pole is bleeding voltage over to the start pole, it could remain on even with no signal (I've had this happen before, but it was on a racecar). The diode eliminates this possibility.

Ambient temperature could cause a problem with the relay if there was moisture or corrosion on the internal contacts of the solenoid/relay.