Salutations.
Well I just spent an hour typing on this stupid phone, my trucks history for this question only to find out I got logged off, and lost all that. So I will try the truncated version and try to answer all the resultant questions that probably were answered in my "lost" previous missive. Blah.
I have a 1994 3/4 ton, straight cab, 2WD, Auto trans.
Two year old starter. New batteries. Jumper wire where starter relay should be. Occasionally something makes a single click each time switch is engaged. Starter does not spin. Mostly when engine is hot. Either I can wait a bit, or cycle the switch repeatedly until starter engages (much faster). Has done this for 4 years now, so I don't believe its the starter. But it has always been very sporadic and random, so have lived with it. Until last week, and again this morning, when after having set for a week, the truck did the "click" thing. Last week took several cycles of the switch to get it to start. The rest of the day was fine. Only had to to the cycle thing twice later, but it was hot out, and I had just gotten off the highway.
This morning I spent almost half an hour trying to get the thing to start. It tried once in the middle of my repeated cycling of the switch, but did not try again when I conscientiously turned the switch.
I tried using the horn relay as all the relays have the same number on top in the starter relay spot. It fit, but when I turned the key, nothing happened. No "click," no nothing. I put the jumper back in, and got the "click" back, but nothing else. I have zero experience with diesels, and am hoping someone here can help.
please? And thank you!

 

Which terminals are you jumping on the starter relay?

 

The jumper in question goes from the plug closest to the cab to the one closest to the driver side fender. I asked the previous owner about it, and he said it was there when he bought it used. Said he never had any problems with anything, so he left it alone. He didn't know why they replaced it, unless the relay failed while on the road, and the jumper was installed to get them home, and it never was replaced.

 

Hhhhmmm...... My problem with that is, jumping the starter relay will have the starter motor running constantly.... Are you sure it's the starter relay that got jumpered?

 

I'm pretty sure... ?

 

Yep, that's the starter relay......

That's just weird...... the way that is wired, it *should* have the starter motor running constantly, even with the key off...... Has the wiring for that circuit been modified???

 

I could not tell you if it has been modified. I'm not sure where to begin. Our Ford dealership is supposed to have the wiring diagrams so I will ask If I can borrow their book come monday afternoon. Then we'll see if I can correctly interpret it. Any suggestions?

 

Download the service manual for your truck from here. Wiring diagrams are in section 8W.

 

Thank you for the link. I will try to interpret what I can.

 

Well I looked over those sheets, and plate 187 is the one I needed.... I think... After much referencing, I could not make out enough information (without the proper education) to assist me. So being frustrated, I figure that if that jumper gets hot, and the starter no longer works. Perhaps the jumper is not stout enough to handle the 12 volt load. So I replaced the multi-strand 16 guage wire with a 12 guage solid strand with soldered on spade connector ends. It was a pain in the rear to get bent right, but I got it to fit, and the truck started. Still not "correct," but it is working. Perhaps when the temps cool down, and I get the master cyclinder replaced on my car, I can tear more deeply into this mess and figure out just what the heck is going on, and why.
Thank you for your help.