He may have 'tapped' his bellhousing and messed up the crank sensor reluctor ring on the flywheel.
Check oil pressure with an oil pump pressure gauge hooked up to where the oil pump gauge sender is screwed into the block.
He ran that eengine at a high back angle for some minutes. Maybee the engine did not 'like' that too much.
DID you crawl under this Jeep to look for physical damage?
"Taking care of our veterans is a cost of war. If you can spend six trillion dollars sending people to war, you can spend a few billion dollars taking care of them when they come home"
Sen. Bernie Sanders (I-Vt.)
If what doesn't kill you, makes you stronger, I should be able to bench press a Grand Cherokee by now!