2000 GMC Sierra 1500 SLE 8 Cyl 5.3L
i put a new fuel pump in but not the sending unit.at first it started great but now its back to hard starting
but if i turn the key on and off a couple times and then start it it fires right up.so i think that it could be the sending unit but i dont know.
The sending unit has no relationship to the fuel pump. It only operates the fuel gauge. You need to read the fuel pressure with a gauge. But before that, replace the fuel filter if you have not replaced it. A clogged fuel filter can give you a hard start.