Is there a reason to add the switch?

 

Pretty hard on it when it is -30C and the relay sticks on a Cold Start.
It has burned out 2 starters cause it keeps sticking. I have put 4 relays in it already.

It would take the switch in the steering column out of the equation. Even if we just tried it for a while. Could easily just put in a switched B+ to the relay and leave the original wire there.

 

The relay problem is caused by cheap junk relays they sell now. When it sticks on you again, run out and pull the small wires off the relay. If it continues to crank over it's not the switch circuit.

 

Yeah it probably is. I am a Journeyman Electronic Tech.
..been fixing Televisions, Radio, Computer equipment for almost 35 years.

 

Well I changed the TPS on Saturday and it fixed up the stalling problem immediately. We will see now if the starter sticks again.

Why would they put the TPS in such a silly place?....or at least use a screw with a 1/4" head on it so one can undo it with a wrench. Had to make a very short screw driver out of a 1/4" wrench and a phillips screwdriver head I ground off.

 

I have found the solution to this problem. In 1990 ford change the design of the starting system on these trucks. The newer square style "solenoids" are actually designed as a relay and are not made to handle the current flow required to spin the starter over. The 1990- trucks actually have a solenoid on the starter and use the square style solenoid to send the start signal to the solenoid on the starter. The pre 1990 trucks use the solenoid to send the power to the starter to spin the engine over. The fix is to find the old style solenoid and use it for the pre 1990 trucks that don't have a solenoid on the starter. Motorcraft SW3 is the old style solenoid. Which is actually a ford tractor starter solenoid. We actually found this solenoid at a tractor parts house for $6. I really hope this helps because this drove me crazy at the shop this past week.

 

The truck is still working perfectly. TPS was definitely the problem.

 

Are the parts stores trying to sell the square style solenoid (relay) to people with the older barrel style relay?

 

Yes they are. This is all banking on the fact that you don't have another problem causing a high starter amperage draw. The truck I figured this out on was a 1988 F350 with a 460. Originally the truck came in with a square style relay that was melted. After I replaced it the starter was drawing 900-1000 amps. After replacing the starter it was drawing 180 amps. But I went through 6 different relays from 3 different brands. Each with the same result. I replaced the the square one with the barrel style one from a tractor parts supply store and no problems since.

 

Replace the relay for possible damage but it isn't fixed yet. The problem, if it isn't a sticking or damaged ignition switch,.. (you can determine this by disconnecting the small ignition wire off the solenoid, if it stops cranking, proceed with ignition switch diagnostics). If it still cranks with ignition wire off & a new solenoid, it is ABSOLUTELY a poor ground to the solenoid! They case ground. Bad ground is low voltage & creates issues. Shine up the metal where solenoid mounts & make sure the fasteners are tight.

 

I thought this was potty until today. I replaced starter, battery, cables and relay on an old F150 I just picked up. Turned the key this morning and the starter kept running. Pulled the ignition wire off the relay and it kept turning. I put a battery disconnect on all my older vehicles so I switch it off to protect the starter. Switched it back on and the starter started turning without the ignition wire even connected to the solenoid. Switched the power back off, beat on the solenoid with a lock I had handy and everything worked. This is bad if even the Ford solenoids are bad.

 

Okay, I know this is old but I found a permanent fix. Adjust the ignition switch on top of the steering column. Adjusted mine and the problem went away.