I removed blown engine and received rebuilt engine and installed all old parts to engine block. After putting rebuilt engine in unit I hooked up all connections from old wire harness and can not get the unit to fire. I removed the four wire plug from distributor module and unit cranked soso I set timing to 0 and replaced the module as the book recommendations were. Still when I plug the four wire into module it does not fire. Removed ecu from a running truck and put in this truck. Still no fire. Also with four wire plug disconnected from module the truck cranks and runs for 30 seconds and shuts off. Oil psi went to 109 on digital gauge. I jumped oil sending unit. Nothing changes. Swapped ecu nothing changes. I'm at a lost point. I traced wires from four wire plug to ecu and ohms match as same as running truck. Engine is a 3.0 GM