2017 GMC Terrain - Reman engine won't work

We replaced engine with a reman and now engine will not turn over, although all electrical works. If key is left in ignition, with ignition turned off, after several minutes, the engine cranks but does not start. We have checked fuses, wiring and all connections and all looks good.

You are saying the new motor has never started?

Description is a little ambiguous. OP, please clarify. Are you saying when key is in “start” position you don’t hear the normal rrr rrr rrr cranking sound?

Please clarify. Are you saying the engine cranks by itself, without turning the key at all? If so, suggest to disconnect battery except when someone is monitoring the vehicle. An engine that cranks and cranks but never starts can cause the starter to overheat & catch fire.

I’m assuming what you mean is that if you leave the key in the “off” position for a few minutes, then turn the key to “start”, it cranks ok, but engine doesn’t start.

No GMC experience, but I’m assuming your starter motor has two electrical connections, a thin wire, and a thick wire. Suggest to measure & report here the voltage at both starter motor terminals, measuring from terminal to starter case. Both should measure at least 10.5 volts with key in “start”.

I’d think installing a new motor would normally involve a competent mechanic. Who might know what to check on a no crank.