Correction to my post #16. It is the primer pump that can create a back or reverse suction force on the relief valve in operation. It actuallty does even when the relief valve is normal.It is the lift pump that cannot .

Unless perhaps if the output valve has failed in it. I think when that happens would have some effect. No way to determine the levels of leakages in this system to allow to remain once detected.

I must have been tired when I reversed the two last night. Important distinction.

If anyone runs across an identical situation in the future. Running the engine on wd 40 should get it self primed up and started fairly easy.