Have you checked all your grounds? go over your ignition and fuel circuits.....have you tried bypassing the wires and put 12 volt and ground right to pump?

 

Make sure it has a good ground.

 

Can you check for power at the pump without dropping the tank? Swap the relays again...
H ave you checked your grounds.....? If it has been the pumps burning up then a bad ground could be the cause...

 

Chevrolet Fuel Pump Failures Explained on YouFixCars.com

 

Since the last time I posted, I've swapped the fuel pump assembly again and went back and soldered the splice connections on the new pigtail harness. I'm still on that same pump assembly, however, I leave the harness unplugged until I'm ready to move the van. Once I move it, I unplug it the harness again until the next time I need to move the van.
So, I would think this confirms my idea that there is an issue when the van is off and the pump is plugged in. I don't read any voltage at the plug when it is off though.
I have checked for a path to ground. I get 0 ohms from the plug to the chassis. Should I be checking for something else?
Thanks

 

fuel pump relay?

 

Replaced it twice. No luck