Does a carbureted engine need a fuel return line?

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asked Nov 18, 2022 in Repairs/Maintenance by JoeBonner (1,400 points)
Does a carbureted engine need a fuel return line?

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answered Feb 16, 2023 by 7maxwarren (12,510 points)
A carbureted engines does not need a fuel return line although fuel injected engines do.

The carbureted engine needs only a fuel pump to lift the fuel to the carburetor level, from the tanks that are below the level of the carburetor.

You can put gas directly into the carburetor although you should not put too much gas into the carburetor or it could cause a flashback and start a fire.

If the engine starts then you have an issue with the fuel system.

Things that causes a carburetor to not get fuel include clogged fuel filter, clogged fuel line, clogged carburetor needle or stuck carburetor float, bad fuel pump.

The fuel line that goes to the carburetor is the pressure hose on the pressure side of the carburetor.

If you have a return line then the return line also goes on the carburetors return line.

The suction line has the fuel filter on it and it goes all the way down to the gas tank to the bottom of the gas tank okay because that line is gonna be used to suck fuel into the carburetor.

Fuel lines don't usually need Teflon tape if you're using compression fittings.

However some fuel lines may need Teflon tape depending on the type of fuel line connector you're using.

You can Zip tie fuel lines to hang them or to also submerge the fuel hose in gasoline or diesel.

Plastic zip ties are fuel resistant and safe to be submerged in fuel.

Nylon fuel zip ties are also fuel resistant and also resistant to most chemicals.

The hose clamps for fuel line should be tight enough so that it's squeezes the fuel line somewhat and tight enough so the hose cannot be pulled off.

Tighten the hose clamp a little at a time and check the hose.

Just make sure the fuel hose clamp is not tight enough to cut into the hose.

You can use polyurethane tubing as fuel line as it has exceptional resistance to most gasoline, oils, kerosene, and other petroleum-based chemicals, making PU tubing and hose an ideal choice for fuel lines (although additives in today's gasoline and petroleum products warrant field testing).

The kind of hose you can use for fuel line is rubber fuel line hose that is rated for fuel.

SAE 30R7 hoses are designed for fuel.

Rubber hose that is rated for fuel can be used for return fuel line as well as pressure fuel line.

When using rubber hose for fuel line pressure make sure the rubber hose is rated for the fuel under pressure.

However any fuel hose that is rubber will be okay for fuel return line.

However just note that regular non fuel rated rubber vacuum or heater hose should never be used in fuel applications.

The hose will deteriorate from the inside out and can plug fuel filters and carburetors with rubber debris, long before it springs an external leak.

SAE 30R7 hoses are designed for fuel.

These can go under the hood and are typically used for low-pressure applications like carburetors or a fuel return line.

It can also be used for PCV connections and emissions devices.

SAE 30R9 hoses are designed for high-pressure applications like fuel injection systems.

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