Our 1994 F150 extended cab has refused to start (consistently anyway) for over a week now. Won't crank, just clicks. Checked the battery - good. Starter - good. Replaced the solenoid, replaced both the positive and negative battery cable terminal ends (what ARE those things actually called, btw?) just in case there was an issue there, and checked the fuses. Only way my husband got it to start at all this past week was by crawling underneath the truck and using a wrench to jump/span the starter directly (and once he used my son-in-law's jump box when he happened to stopped by.) The last time he was under the truck he happened to notice a wire (encased in a plastic/rubber sheath) that felt like it might be broken, so he stripped the sheath off to get to the wire inside and sure enough it was broken. Evidently the sheath had held it in place just enough for it to make an occasional connection. Anyway, he spliced it back together, and the truck started just fine. It fired right up as soon as he turned the key in the ignition without any hesitation or hiccup. First time he was able to start it using the key in the ignition for over 8 days. Lol. He tested it to make sure it was starting fine by shutting the truck off, waiting a few minutes, and then starting it up again. He did this several times and it started right up each and every single time he tried/tested it. So he finally went ahead and taped up the spliced wires real good and..... you guessed it. Now it won't start again. Arrrgggghhhh!!! Please help!

I think I start with replacing that whole wire wherever it goes or comes from as you never said.

Sorry about that. I felt like I thoroughly "interrogated" my husband before posting my question so I could provide as much information as possible, but I obviously didn't ask quite enough questions. 🙃 I just now talked to my husband about this and he said it was the wire that provides power to the solenoid, but he said he replaced the whole wire after splicing it didn't work. Still won't start.

He wants to know if this problem could be caused if the starter is not firmly bolted/grounded to the transmission? Thanks for replying. 🙂

If you can successfully start it by shorting at the starter, then you know that battery power is at the starter on that side. Look for corrosion on the ignition circuit. Make certain the ends of the connectors are clean and tight.
Do you have a multi-meter capable of diagnosing a voltage drop test?

Check/replace the starter relay, located in the under hood fuse/relay box.