s-10 won't start.

i have a 91 s-10 that has a 4 cyl. in it. i have to dump gas in the carb. in the mornings to start it. it will start every time after that until the next morning or if it is cold out. i have put a new fuel injector in it and a new fuel relay in it and plugs and wires, but it still won't start. i have no problems with it running after i dump gas in it. any ideas?

Seems like gas is not staying in float bowl of carb. Needing engine started like you do that fills upper gas line and float bowl up. Question is why is it not staying up there maybe.

Or, could the electric sending unit at tank be failing ?

91 would be a throttle body, not a carb. Change the fuel filter?

Agreed, 91 is fuel injected (tbi) not carbed... That said, does it start normally if you simply turn it to the run position for a couple of seconds before engaging the starter? Your fuel pump may be weakening. I would also check the pressure regulator.

to see if it is the fuel pump turn on the key and listen for it. If you son't hear it shut off the key and take a hammer handle and hit the gas tank(firmly but not real hard) in the area of the pump. then turn the key and see if you can hear it. if you can know then your pump is almost dead, or prob is by now.