55.2-59 Not getting fuel from Holley external pump, help gents!

[daveshilling]

Hey fellas,

I have a 59 GMC parked out on the street and I need to move it to the driveway today or else the city is going to move it elsewhere.

The 270 runs and ran when I got it. I cleaned up some of the patchwork wiring and replaced the gunked up gas tank. It was running on crappy, confusing wiring and bad gas.

After scrambling to reassemble the wiring, I get no fuel from the pump, even when i manually put the positive directly to the battery. It has pumped a small amount of fuel, then stopped. The previous owner installed a second tank with a 3 way valve, and I have it switched to the in-cab tank (no matter where i switch this valve... no fuel)

I've removed the inline fuel filter in the line leading to the carb, pointed the fuel line into a coffee can, and put the fuel pump line on positive battery. The pump runs, and it has spit out a bit of fuel, but it then sounds starved and no fuel comes out.

Dumping fuel down the carb gets me running briefly, so this is the last puzzle piece.


First stupid question.. how much gas needs to be in the tank? I put in a few gallons, but I don't know how much needs to be in there to reach the inlet tube.

Second question: Where should the positive line of the fuel pump be wired to? It was connected to the bottom of the resistor when I got the truck and it was running, but that doesn't seem right.

Any other insight is helpful! I have until 830am tomorrow to get this bad boy on the driveway. The driveway is inclined, there is no pushing this truck.

[MiraclePieCo]

One possibility is a leak in the fuel line upstream from the pump. The pump will suck air in the leak instead of gas from the tank.

Tighten all the fittings and hose clamps. Replace any cracked hoses.

.

[mr48chev]

If you fill the float bowl with gas (through the little tube in the throat) it will usually run for close to a minute. It might take a couple of tries but that might work to get you in the driveway.

I'd agree with the line sucking air between the pump and the tank. Ol hoses that are cracked or a loose fitting might be the cause there. If you have air available that you can reach the truck with you might try blowing air in the filler neck for that tank and see if you can push fuel through the line to the carb. It may be that the pump just won't prime on it's own because it has been dry for too long.

I've seen the pickup tube in a tank broken or rusted off before and I have seen plugged up pickup screen socks that go over the tube a lot of times and trash in the tank that would plug the pickup tube a couple of times.

[geezer#99]

Your 3 way valve could be sucking air in around it’s seal.
Simply bypass it with another hose or short piece of tubing.

[daveshilling]

Thanks for the suggestions gents! I rigged up a line from a gas can directly to the pump, eliminating the valye and any leaks in any of the associated lines, and it did not pump the gas up from the can towards the carb.

I switched to gravity feeding the hose leading to the carb with a water bottle instead and bypassed the pump entirely... this seemed to add too much gas and it wouldn't run for very long when started. Squirting a bit of gas into the carb did work better but not well enough to run (it didnt run well in the first place, but it would get going sometimes.. not this time.) Maybe I missed the bowl!

This is my first carburated engine, so it's definitely a learning opportunity!

We ended up pushing the truck onto the driveway with another vehicle as a last resort, and now I can troubleshoot in peace, and shade. The carb rebuild kit arrived in the mail today, so that will be an adventure I'm sure!

[1project2many]

Since the immediate issue is to get the truck into the driveway, I would try to follow Mr48's advise about filling the carburetor bowl.

Next I would take baby steps in diagnosing the pump. Using a short piece of hose I would connect the pump directly to a can with fuel. If the pump draws fuel out of the can then I would move on. If the pump doesn't draw fuel it's most likely bad.

Next I would check the conections between pump and tank. I would bypass the three way valve and add additional fuel to the tank, maybe 5 gallons max, and check to see if the pump draws fuel.

If the pump draws fuel I would reconnect the three way valve. Check again to see if the pump draws fuel.

If the pump draws fuel I might believe the fuel level was too low previously. If not then the valve is bad.

By breaking a system into small bits then testing each bit individually it's usually possible to rule out what works while pinpointing what is bad.

[geezer#99]

Why an electric pump?
It could be putting out too much pressure.

[daveshilling]

Originally Posted by geezer#99

Why an electric pump?
It could be putting out too much pressure.

That's just what was on the truck when I got it. Previous owner had a second tank out back and a 3 way valve to switch between them.

I contemplated switching back to the mechanical pump that is still attached to the engine. I don't know if that pump works or if it will need to replaced, but it would definitely simplify things. This truck will be for sale at some point so I don't want to invest too much into it if the next owner tosses the 270 and wants to put in a small block.