Hmmmm, That is weird.
Something in the T setup or whatever you did for your electric pickup that won't allow the stock pumps to prime?
Is there a check valve in the electric? Could the stock pumps be trying to pull a prime backwards through the electric?
Pinch the supply to the electric and see what happens.
Dono, Just guessin here.
I know the RX pumps wont allow fuel to pass through them unless they are pumping. All my two strokes will. I always prime the systems by blowing into the tank's vent line (fill cap on and tight) with lung pressure. Fills the carbs right up on the two strokes. On the RX I put a bypass tube in to go around the pumps. Do the vent line blow to fill the carbs. Hook up the pumps and I'm off to the races.
You've got a new one I haven't seen.
Good Luck, opsled