01 5.3 4x4 Ext cab.

swapped the engines with known good engine with 79k. Original list all oil pressure at 400k. Had it running but pretty rough. Had to swap alternators and forgot to disconnect the battery and let the wire ground out had some sparks. Checked all the fuses took care of the blown ones and now I’m at a loss. I’ll have power to my dash and lights and cluster i turn the key the rest of the way to start the truck and I lose power and everything dosent work and hazards light up but don’t flash. Head lights quit working but running light and tail lights will work. Any have anything constructive to chime in.

 

How about the mega fuse? Did you check that?

 

The alternator - it has an integrated (computer / voltage regulator) that could be shot. They are usually replaceable not too expensive. I'm unsure if that could cause your issue in this case or not - since alternator voltage being hi/lo isn't in play during CRANK.

during CRANK your car's electronics go in a special mode until CRANK is successful. your electronics aren't "connected the same way" until CRANK has finished. (this is why i think check battery, starter, alternator - the usual "no start" items first). you can find a diagram of what is wired how during CRANK. you might even find your starter is wired wrong and your alternator is not even the issue - after a motor swap. and after a motor swap i'd crank a few times by hand to insure the motor is rolling over normally before anything else.

hazard lights work off a "blinker" thing (the very same as turn signal) - they are like $7 - they do go bad but likely that's not the issue of course. if the hazard lights don't blink ? that means the lights are getting power but the "blinker" (under the dash) isn't flipping the power and maybe isn't even in the circuit (no ground power routed to it so it is not switching ground) currently. DURING CRANK: bet they don't get ground. so ignore the hazard lights.

really - letting a few sparks happen momentarily shouldn't blow anything major out. i've done it countless times on many vehicles. I've put the battery on backwards momentarily, let hot connect to ground doing an alternator or starter momentarily. i've arc welded without disconnecting battery. you name the fool i've done it. no problems.

The clue I see is that you turn the key to start and power is lost: in those conditions i would check the battery, battery connections, fuses, starter, fuse panel for possible loose or burned wires. I assume you already looked at all the alternator wires back to the fuse box for issues and no burned wires seen.

fuse panel: can and should be used to isolate an issue. disable "everything" except what you need. re-enable one at a time. you have 3 fuse / wiring panels in that thing. use them.

less likely: consider the BACK of the fuse panel isn't working or burned. it's a big job to check the backs of the 3 fuse or wiring panels in the truck. you'd probably find a way to "get around it" (test parts by connecting them without the fuse panel) to see if they work before doing a whole fuse panel investigation.

 

I would first double check all my engine install points. Your not starting if you forget to plug in the tranmission connector or oxygen sensor.

I would not rush into blaming the "spark" for the no-start. Check the simple things first.