[Rich Biebel]

No relay.
Pump is run direct from the board.
Those pumps do not have very good suction
I've had problems after doing a repair getting fuel to the generator when the tank is a good distance away.
Had a semi type truck earlier this year with a side saddle tank and after having the generator out for repair I could not get fuel. I pressurized the tank and forced fuel over to the opposite side where the generator was. Once fuel was there it was ok.
I've had the same thing happen in toterhomes with rear mounted generators and tanks up front.
The pump would be better if it was mounted near the tank but that's not practical.

There can be NO air leaks in that fuel line......wherever there is rubber and clamps they need to be tight and the right size. I often see rubber fuel line to large for the steel portion they connect to.
A 1/4" fuel filter and a 5/16" rubber line.

I've also seen both older and nearly new Motorhomes with some kind of fuel tank pickup issue. Generator won't run off fuel tank but will run off a jug of fuel located near the generator.....

I have blown air into the fuel line back to the tank and used air and a rag to lightly pressurize the fuel tank to see if fuel comes out the generator supply end.....

If you changed the pump and the board, the tank and line are where you need to look.....

I have even resorted to adding a second pump on a couple vehicles.....ones that had a long run or a big lift....

I have seen some vehicles with pumps factory mounted near the gas tank....Those were gasoline units.....

An inline check valve might help but I never tried to make that work.....