Only runs while pouring gas in carb.but gas is coming through fuel pump why will it not run

The carb is not letting gas into the engine. Rebuild the carb.

Disconnect the fuel line from the carb and turn on. If no fuel comes out of the hose, the pump is bad.

Throttle body or carburetor ?

Well if the pump works then follow the pump fuel lines to the engine,you will find the fuel filter then replace it and will also see petrol if any in it ,if not pump isent working ,if dirty replace it and blow air back from carby to filter to clean out pipe
,turn on ign fuel should come to filter and then with new filter in turn on fuel and see if any comes to carby if ok it should start and run.
Have a goodday,

Which model is it? All fuel pumps are either run electrically or mechanically so you shouldn't have to prime it unless it's the carburettor you mean?

Sounds like the fuel pump is bad. The engine is just not getting fuel unless you pour it in the carb.

get a oil can the thumb operated type and squirt some oil down the petrol pipe and make sure pipe is upwards so the oil runs into the pump then leave for a while to wet the valves in the pump then crank engine to make sure petrol comes up or just refit the pipe and pour some petrol down the carb and watch it go

rebuild or replace the carb- it isn't working properly. You may just need to clean it good as there may be a partial blockage.

This truck is fuel injected, the problem sounds like a weak fuelpump, it runs when you pour gas into it until that gas runs out, the first thing is to test the fuel preasure, if the pump is weak it may run with gas poured into it but wont idle, also a common problem is the coolant temp sensor and the ground wires to thermostat housing bolt but i wont bet its the pump inside the fuel tank, if you put a fuel gauge on it there should be at least 55-61 psi if its a few pounds lower it can cause problems, you have everything else and it runs with gas poured so its a fuel problem check the preasure, theres a valve up top on the fuel line to connect a fuel gauge to it, start there hope this is helpful.

Fuel pump electric? Check the oil pressure sensor/switch