Engine will not crank or start
 

We have a 98 vortech 4.3 blazer we did a engine swap on with the same type of engine but we can’t get it to crank unless we jump the starter. We’ve replaced the ignition switch, positive battery cables, starter, it is getting fuel and spark but only starts when you jump the starter. The engine is not blown because we have had it running before but it doesn’t want to start with the keys. Only when it is jumped will it start. Can somebody help me with this, Thanks !

Where are you "jumping" the starter to get it to crank? At the starter itself between the large black power cable and the smaller purple wire/terminal?

If so we just walk through the circuit that applies power to the purple wire at the starter and find out where the fault is, Start by measuring the voltage at the crank fuse in the underhood fuse panel with the ignition in the temporary start position.


George