reading this over again pisses me off, I kept all the goings on behind the scenes until I gave your company every chance to make good. Do I piss and moan about it now? you're fukin right I do, and you step right up and show people how you treat some customers.
You have a dead short. The easiest thing to find. Unplug the motor, replace the fuse, turn on truck, and see if the fuse still pops? If so, you have a bad motor.
Fuel is a weak conductor. It may be loading when pumping, but that would be a bad bearing structure creating that issue.
That also wouldn't be instantaneous.
From my Not-So-Smart phone
Was it wet? How about a serial number? I'll check to make sure it's not an updated/current pump. And they were all 3 like that?