Truck has been sitting for about five months and I just rebuilt the carburetor. The truck will start and run on the gas I pour into the carburetor. The gas gauge sits on empty and it shuts off after 10-15 seconds. The fuel pump was replaced four years ago, could this be anything else besides the fuel pump or fuel lines that I’m not thinking off?

 

Welcome to FTZ! This is a complete way to check your fuel transfer system tank to carb. First put 5 gals of gas in the tank.
A suggestion, at any auto parts store you can buy a Fuel Pump/Vacuum tester, Very Reasonable and useful test tool to have at other times. Getting a Multi Step hose connector AND Tee will help make all test connections.

I would start at the fuel pump Inlet Fitting, attach to where the flex hose goes on. Crank the engine , vacuum should build and hold after cranking stops. If so, the pump is working AND the Inlet Check Valve is Good.

Next is to check Output Pressure of the pump. I'd hook tester to the steel line where it goes into the carb. Again, crank the engine, pressure output should be 5 to 7 #'s and hold after cranking stops. If so, the Output check valve is good and you can say the fuel pump is OK.

Next remove the rubber hose at the Fuel Tank. Attach the tester to the Hose. Crank the engine over till maximum vacuum shown on the tester. IF good and holding, consider all from the Carb to the Tank Outlet is OK.

IF, there is no vacuum, you have an Air Leak OR Obstruction between the hose at the tank and the hose at the fuel pump. Look for the steel line being rusted thru some where along the frame, possibly at a support clip.


To check and see if there is a problem within the tank, you need the plastic TEE and short piece of fuel hose. At The Tank, attach the Tee to the rubber hose, to the short rubber hose on tank outlet the lastly to the vacuum gauge. Crank engine over, IF you have vacuum, there is an obstruction, no vacuum, all is good with tank.

One more thing after, Cap

 

In My last post, the last paragraph, the last sentence. It needs more clarity, I wrote, "Crank engine over, IF you have vacuum, there is an obstruction, no vacuum, all is good" with tank".

I should add, Also if you have vacuum and it falls off after cranking, that may be fine,as the fuel in the tank is not an obstruction.

Kinda long and drawn out, I know, but that's me.

A quick test, no gauge, gas can on the ground, fuel hose to fuel pump inlet, prime carb and start, at least a couple times. If engine keeps running, problem is between the pump inlet hose and tank. If it keeps shutting off, check for the Float and Needle seat in Carb being hung up/ stuck not allowing fuel into the carb,

Let us know how you make out, Cap