Fuel delivery troubleshooting

[cadillacdevic]

Hello! New to the forum.
I have a 74’ C10 that I’m trying to figure out why I’m not getting fuel to the carb. I have a duel tank and I can hear it switch when engaged but no fuel when I turn the key and pump the gas.
Any suggestions?

 

[Chevy 88]

Empty tanks (incorrect fuel gauge)
Hole in fuel line
Bad fuel pump
Clogged fuel filter
Clocked carb inlet fuel screen
stuck float
Missing fuel pump push rod
Clogged fuel tank outlet tubes
Vapor lock (vacuum in the tanks)

That's all I can think of.

 

[Ricko1966]

Hello! New to the forum.
I have a 74’ C10 that I’m trying to figure out why I’m not getting fuel to the carb. I have a duel tank and I can hear it switch when engaged but no fuel when I turn the key and pump the gas.
Any suggestions?

Have you ever driven this vehicle before? Have you ever owned, and run a carbureated car with a mechanical pump out of gas before? Usually you will have to prime the carb,sometimes more than once to get them to start if the pump and lines have been run dry. Do you know methods to prime the carb,or you already tried that. From your description I can't tell if you are turning the key to run or cranking. These trucks are not like injected vehicles,turning the key to the run position does not run the pump.

 

[Grit dog]

Have you ever driven this vehicle before? Have you ever owned andvrun a carbureated car with a mechanical pump out of gas before? Usually you will have to prime the carb,sometimes more than once to get them to start if the pump and lines have been run dry. Do you know methods to prime the carb,or you alreadybtried that. From your description I can't tell if you are turning the key to run or cranking. These trucks are not like injected vehicles,turning the key to the run position does not run the pump.

Hopefully the OP will endeavor to provide some info to help us diagnose his issue. In the meantime @Edelbrock gave him a good top 10 list to work through since no info or descriptions by the OP to help us not have to be completely clairvoyant.

 

[fast 99]

Hopefully the OP will endeavor to provide some info to help us diagnose his issue. In the meantime @Edelbrock gave him a good top 10 list to work through since no info or descriptions by the OP to help us not have to be completely clairvoyant.

My crystal ball broke a long time ago.

 

[Ricko1966]

Empty tanks (incorrect fuel gauge)
Hole in fuel line
Bad fuel pump
Clogged fuel filter
Clocked carb inlet fuel screen
stuck float
Missing fuel pump push rod
Clogged fuel tank outlet tubes
Vapor lock (vacuum in the tanks)

That's all I can think of.

Vapor lock is not vacuum in the tank. But Vacuum in the tank is not good.

 

[cadillacdevic]

Have you ever driven this vehicle before? Have you ever owned andvrun a carbureated car with a mechanical pump out of gas before? Usually you will have to prime the carb,sometimes more than once to get them to start if the pump and lines have been run dry. Do you know methods to prime the carb,or you alreadybtried that. From your description I can't tell if you are turning the key to run or cranking. These trucks are not like injected vehicles,turning the key to the run position does not run the pump.

Yes, I have driven it. It was fine the last time I drove it. It sits more than drives these days. Usually pump the gas a few times and starts up. Filter is dry and I pull the lines with the key in and no fuel.
Thinking of bypassing the tank switch.

 

[Ricko1966]

Yes, I have driven it. It was fine the last time I drove it. It sits more than drives these days. Usually pump the gas a few times and starts up. Filter is dry and I pull the lines with the key in and no fuel.
Thinking of bypassing the tank switch.

Key in does not make the pump run,the pump is mechanical and operated by the camshaft which is only 1/2 crank speed. What carbureator do you have on it. I bet you need to prime the carb.then once the engine starts on prime the mechanical fuel pump is working fast enough to draw and move fuel.

 

[Grit dog]

Yes, I have driven it. It was fine the last time I drove it. It sits more than drives these days. Usually pump the gas a few times and starts up. Filter is dry and I pull the lines with the key in and no fuel.
Thinking of bypassing the tank switch.

This would be a lot easier if you responded more.
Do you have an electric fuel pump? Or are you confusing the term “key in/on” with cranking or turning the engine over.
And bypassing the tank switch is like starting at the back of the line and working your way forward.
Assuming mechanical fuel pump start there. Is it pumping gas or not? A hose connected to the pump stuck in a Gatorade bottle of gasoline will diagnose that before you start messing with the tank selector switch and valve. You haven’t narrowed it down to that yet and sounds like you may not understand how it works because I don’t understand what “bypassing the switch” means.

 

[75gmck25]

On a dual tank truck there are multiple short rubber fuel hoses. They are old, and may have cracks or holes in them. Modern fuel with ethanol makes them deteriorate even faster. The mechanical fuel pump pulls/draws fuel from the tanks, so any leaking hose can cause it to draw air instead of fuel.

Put the tank selector on main and make sure there is 5-10 gallons of gas in the main/passenger side tank. As explained above, disconnect the fuel line to the carburetor and replace it with a longer rubber line running to a large bottle or can. Use the key to crank the engine over for 15-20 seconds , then pauses and crank again. If you don’t get fuel into the can, then post back with the results.

Also- pull the air cleaner off, hold the choke open, and use the cap from a spray can to pour a cap full of gas directly into the carburetor primaries. Replace the air cleaner to catch any backfire. Then crank the engine with the key and it should start, or at least fire with the fuel you just poured in. If the fuel pump is working, it should also push fuel up to the carburetor.

 

[xm20k]

Mechanical fuel pumps take a few rotations to pick up and make fuel pressure especially if it has sat untouched for a while and fuel drains back and or evaporates from carb. Like others have said pull the line from the carb and run it into a bottle and crank it over a few times and see if the pump is moving fuel, it may take a few tries depending on how long it has been sitting.

Mine feeds from a fuel cell in the bed as it sits higher than a stock tank and keeps the line full to the pump, but the pump still takes a few rotations to fill the bowls and build pressure if it's sat for more than 2 days.