1989 Suzuki Sidekick 1.6/5-speed

This is driving me insane. Truck cranks and runs normally. I drive it, all works as expected. If I turn it off, sometimes it starts again, sometimes it doesn't.

Yesterday I drove it. Came home turned it off. Immediately started it again and it started normally. Turned it off, immediately tried to start again and nothing. It turns over, but never starts.

Luckily it finally did it in my driveway so I could troubleshoot the thing. Injector is pulsing gas, I have fire to the plug wires. Just spins with the starter doesn't even pretend to fire. I messed around with it not starting checking different things until it was cool, still not starting. I went inside, came out 2-3 hours later. Truck started normally again.

It has fuel, fire and compression (~135# on each cylinder). What am I missing with this thing that it randomly starts or doesn't?

Thanks.

shot in the dark here but maybe check your ignition switch ?

When you turn on the car, does your Check Engine Light always come on?  If it does not, then your main relay isn't working properly, probably due to a bad ground.

Otherwise this might be a computer problem.  The older Sidekicks have problems with the capacitors on the ECM leaking.  If you can find another 8 valve trying borrowing their computer and see if the issue goes away.

The injector might be pulsing but does it have fuel pressure?

Try start it bypassing the ignition switch! Look at the starter, there is small wiring connection remove it and put a separate wire (Around two meters) and another end of the wire to the battery. Does it start??