1961 Chevy Truck universal external electric fuel pump

hmmm a ford engine in a chevy? you can have a couple of problems here. there should be a vent to the float bowl in the carb,and that could be plugged but idoubt that. Does this have a fuel filter on it? it could be plugged. Aslo you could have a pressure regulator before the carb and it may/could be set to low. Also you could have a needle and seat in teh carb sticking. Try tapping on the carb when the fuel pump is on and see if that helps. You would do this where the fuel enters the bowl. One other thing could be crap in the carb making this happen. Also it depends where the pump is mounted and if the gas tank vent is plugged as well. You could also try taking the gas cap off and seeing if it would help, then it would tell you the gas tank vent is plugged.

Ford motor in a Chevy... I know, I know ...[ it's actually a '49 body & frame] but the only way I could escape the constant ridicule of driving 'one of those sissie bowties' was to change everything over to Ford.

Thanks so much for the good suggestions. Because of this problem, I took my carb. to be professionally rebuilt, and instead traded mine for another already rebuilt unit. I previously installed an aux. gas tank in the rear in addition to the original behind the seat and have filters on each supply line before the tank selector valve. I also had another filter, regulator and gauge at the carb. but I replaced that group with clear line to see what was going on. [I was maintaing 4# pressure even without any gas ??]
But you might be on to something concerning the fuel pump placement.. it is mounted inside the frame under the passenger seat...I remember having problems getting it to work correctly when I first put it on [about 5 yrs. ago, but it finally mysteriously started working... maybe it needs to be moved one way or the other ??
Again, thanks for your help, & if you think of anything else, please pass it along.

the reason you have 4# of pressure is due to the regulator, I would take the fuel filter off the carb if you can as you have suffiecient filters in the tank lines. I'd also try withouot the regulator as you may not need it. Then make sure you have good lelectrical connectiions to the fuel pump itself. Like a good ground and power. AS being mounted on the frame you can get corrosion and stuff. Use star washers for the ground to poke into where ever they are mounted.

I'm beginning to think my truck is possessed... I now have a new filter at each tank discharge, a new fuel pump selector switch,[with gravity-fed fuel flow on discharge side of switch for each tank selection] and another new fuel pump.
With regulator and gage and filter at carb. all removed, and replaced with clear line, I can pump from my aux. tank but not the other. This is not a pressurized system so I don't understand what can be happening.... I don't want to disconnect this main tank but at least I can now drive on the aux. tank. Thanks

It really sounds like you don't have any or very poor venting to the main tank, especially if you can run off of one tank and not the other. Make sure this has a vented gas cap on this tank and not a non vented one. If it is a non vented cap it will suck the tank together if it's asheet metal tank. That would be the reason for no fuel as well. I think I hit on that previously, maybe not.

finally found the problem... of why I was running out of gas
when I installed the rebuilt carb..I relocated the fuel line slightly to keep away from the heater hose that almost touched it.. the new location at one point was about 1/2 " above the carb. fuel inlet. As the fuel pumped, the air bubbles in the gas in the non-pressurized system would collect at the highest point instead of venting when it got to the carb. This air bubble would grow in the line, causing the pump to quit sending more fuel. ... I lowered the fuel line on the firewall and the problem disappearedThanks again for all the imput and suggestions

at least you found it . good for you. Next time you'll know.