2002 malibu. changed engines . this one will start if you disconnect the neg wait 10 - 15 mins and bob,s your uncle it starts. Now if you shut it off and restart it 20 seconds later it won,t start until you disconnect and reconnect the neg. also the tach should be working but nothing.

Try checking your starter wire that runs off your negative battery cable. Follow it all the way may have a bad spot in the wire. Or the cylonoid may be bad. Both of those things would cause your issue.

Definitely a electrical issue.

Well peoples, my problem seems to have been fixed. I was looking at the 2 sensors that are on the front of the engine and unhooked the oil sensor tag first and tried starting the car, low and behold it started like it was suppose to. Changed the oil sensor from the engine i took out and everything seems to be good. keep you posted...