A short somewhere, insufficient wire thickness causing too much resistance... try upgrading it to a larger gauge wire.
The starter will crank the engine over but it won't run.
It is bolted in the passenger side of the engine block RIGHT BEHIND the starter. You can not see or get to it untill you remove the starter.
your crank sensor has absolutly nothing to do with the ability of the engine turning over. I would look at the wiring to the starter.
Assuming the starter does not crank over the engine, it could be, dirty or loose battery connections, a bad starter, a bad neutral safety switch, the engine is seized.
Sounds like a starter issue. Bad wire to the starter could cause it.
Test your battery. If that checks out, take off the starter, take it to Auto Zone, and they will bench test it for free.
starter going out or poor voltage
the truck will not crank or anything with the key it wont even starter when you ark the starter all it does is whizz
"Crank" meaning the starter doesn't crank the engine over to start it, changing the engine oil should have nothing to do with it not starting. If the battery was weak and something was left on, it may have run the battery down. Also check the engine oil level to be sure they put new oil back in or possibly left the drain plug loose and the oil drained out. If the engine was run with no oil in it, it could have seized the engine and it wouldn't crank over, in which case the engine is ruined.
Typically water in engine.
Need to know what year it is, engine size
Passanger side, lower part of the engine.