1998 Ranger, 3.0 liter manual transmission.

The vehicle recently has had the engine replaced. Still a 3.0 Liter, but possibly is from a 1995 or 1996 Ranger. Replacement motor from a wrecking yard, appears to have been sitting for quite some time prior to purchasing.
I had a friend change the motor out after getting the vehicle a few weeks ago.

Ranger drove fine for a week, but this morning it wouldn't start. One click is all it would give when you turned the key. Thinking the culprit was the all in one starter/solenoid, I replaced it with a new one this morning. Now the solenoid will click continuously when the key is turned, starter still will not rotate then engine.

Battery tests good - 12.4 volts; connections appeared fairly corroded.

Here is what I have done:
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Clipped off the first half inch of corroded terminal leads, replaced both sides with new battery connectors and wire brushed connections off at battery and starter.

Replaced Starter

With "S" connector disconnected, attempted to bypass starter connections and short terminals to see if a faulty clutch position sensor was to blame; shorting did not produce anything other than turning the key did.

Paralleled an additional cable from battery to starter terminal to see if corroded wire connections were to blame; still just clicked repeatedly when attempting to start.

Crankshaft does rotate manually, does not appear to be seized up.

Unsure of what else to check for. Not confident in friend's engine installation abilities, he may have screwed up something I'm not thinking of.
On the other hand, I don't believe I would have been capable of swapping out the motor myself.

 

Welcome to FTE.

12.4 volts, unloaded, across the battery posts = less than 80% soc on the battery, so its not fully charged.

Those temporary battery cable post end clamps are for temporary use only & are prone to all sorts of contact problems.

Turn the head lights on, blower motor on high speed & test under load voltage across the battery posts & post the number.

That said, along with you reporting corrosion on the battery post clamp ends & wire strands, makes the battery to engine, body & B+ under hood power distributon box to battery connections in question.

Good idea to try the battery cable parallel connections.
So, one at a time, try using a really good quality heavy gauge jumper cable to parallel the engine to battery Ground cable & starter motor to battery B+ cable & see if it'll make any difference.

Do the dash lights dim badly when you try to crank the engine. If so, connect your multimeter arcoss the battery posts & position the meter so you can see it from the drivers seat when you try to crank the engine & note if you get a big voltage drop. If so suspect a bad battery cell or internal high resistance electrical connection to a cel causing under load voltage drop that didn't show up with just the head lights on, or a starter motor problem.

Review the how to do voltage drop testing with your multimeter, in the Battery Tutorial atop this forums index page for other testing & let us know how it goes.

 

Excellent insights -
I neglected to test the negative connections the same as I did with the positive. When I ran a jumper cable directly from the negative terminal to the engine block, the vehicle started up.

Upon further inspection, I found a dangling ground by the starter, and a corroded and loose braid going from the motor to the frame.

Under load, the battery reads 11.53. I'll keep an eye on it just in case.

All in all, I'm fairly confident this was the result of insufficient grounding from the engine to the battery. To be safe, I'm going to disconnect all connections I can get to, brush them clean and reattach them.

Thanks!

 

OK, good trouble shooting & feedback. Sounds like you have a good grip on your problem.