I have seen this issue bejabbered to death on various forums, but seldom with any procedure to diagnose or any solution attached. So here is how I solved it:
As the title says, our 1993 Toyota with 22RE just wouldn't crank or start one day. It did for a little while after that but then a few days later it was as dead as a doornail. Just in case we wanted anything to be easy, the only FSM we could find didn't have details of the wiring for that circuit
To troubleshoot an electrical gremlin like this, it's really important to change one and only one thing at a time, carefully testing all your assumptions.
Step 1: We found the starter relay in the passenger side under-hood fuse box. Took it apart and applied 12V and verified that it works. Terminals were clean. Re-inserted and still no crank.
Step 2: I squeezed under the truck and probed the starter wire with a diagnostic light. 12V never arrived at that wire at any key position.
Step 3: When the ignition key was cranked, we thought we heard said starter relay click, which led us down the wrong path for a while, Turns out the click was coming from the EFI relay
Step 4: After realizing that the EFI relay was the only one clicking, we were back on track. Pulled the starter relay and jumped the normally open terminals with the ignition key at "ON". The starter motor spun; As a double check we put the relay back and turned the key to "START". No crank or anything.
Step 5: This pickup has a clutch interlock switch that prevents any starting if the clutich is not depressed. In the past I have been stranded by it failing, so we tested this switch and it is good. Just to be sure it was not the problem, we shorted between the two terminals and attempted to start the truck. Still nothing.
Step 6: Unfortunately, we didn't have a pinout of the ignition key switch. So we took a multimeter and figured out which terminal was 12V in. Then which terminal was connected to 12V in if, and only if, the key was at the START position.
Step 7: We then tested this wire for continuity to the control terminal of the underhood starter relay. Nothing. Reinserted the relay and no crank
Step 8. Staring at the dismantled dash, I saw a little black box attached to the wiring I was just testing. Turns out for whatever reason, there are
two starter relays daisy-chained together!
Step 9: Pulled the under-dash starter relay. Applied 12V to the control terminals and verified continuity between the NO terminals. Contacts were a little crusty but really not bad
Step 10: Re-inserted the under-dash starter relay and attempted to start. Nothing.
Step 11: Re-removed the under-dash starter relay and tested for continutity from its wire to the control terminal of the under-hood relay, and found continutity. Re-inserted the relay and attempted to start the truck. To everyone's great surprise and disappointment, it fired right up
Our electrical gremlin was gone without much apparent progress. We had checked everything we could think of at that point and found it good, but hadn't changed anything to make the truck work again. Except.... we had. Removing and re-inserting the relay and the position of the wires in the harness while fiddling with the relay there were the only things that had changed between no cranking and cranking.
Step 12: While putting the dash back together to await the re-appearance of our friendly local electrical gremlin, a crimp connector on the ground wire for the under-dash starter relay just fell apart. Well, the crimp connector is fine but the wire just fell out with gravity. A good solid crimp later all is well with the world.
We could have got out the parts cannon and replaced the starter motor, the two relevant relays, the ignition switch, and everything else in sight to the tune of many, many dollars. Instead all we had to do was crimp one connector. Do your diagnostic work right guys. It'll pay off in the end
