i got something you could try,easy and dont cost nothing.
take a hose clamp tool(i use a needle nose set of vice grips)and clamp the return fuel line to tank at the fuel filter.
crank with a charged battery and see if the engine will start.
if it starts release the hose clamp to test, if fuel is bypassing thru the ip relief valve(if its bypassing then the engine will quit or run real bad.
let us know.
larry perkins lou ky