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What is a Fuel Line?
A fuel line is a hose or pipe that transfers fuel from the storage tank to the rest of the vehicle, generally just transfers fuel.
Usually reinforced rubber to allow flexibility, but also can be made of plastic.
The term fuel line applies to anything that contains liquid or vapor fuel, which makes it more of an umbrella term.
What Do Fuel Lines Do?
Connect all parts of the fuel system
Allow for fuel to get and/or return to various places
Lines are placed in areas that avoid overheating to avoid heightened evaporation
Normally runs from fuel pump to fuel filter to fuel tank
Has a vapor-return line that brings vapor back to the fuel tank
Vapor-Return Line
Line that connects to specialized port on fuel tank to return vapor
Also collects excess fuel to return to tank
Circulation of fuel keeps the fuel pump cool
Some have an in-line check valve, which prevents fuel from going back to the carburetor
Possible Issues Within Fuel Lines
Low pressure or partial vacuums cause fuel to vaporize
Produces Vapor Lock, where carburetor only receives vapor
Vapor goes out bowl vent* and engine doesn't receive gas
Types of Fuel Lines
Rigid Lines
Mostly attached to body frame or engine
Made of seamless steal tubing with steel springs around areas that protect from damage
Should only be made of steel
Copper and aluminum tubing cannot handle vehicle vibrations and they chemically react with gasoline
Some cars secure rigid lines along the frame of the car until it is close to the pump, then a short flexible line bridges the gap and absorbs the vibration
Most cars have a rigid line from the tank to the pump
Flexible Lines
Synthetic hoses are used in systems that require flexibility
Delivery hoses are larger than return hoses (8/10 mm to 6 mm)
Material of lines must be able to resist the possible harm from the fuel vapors
Restricters (either metal or plastic) are mainly on lines for ventilation and are located either on ends of lines or within the hose
If it’s in the hose, then the restricter has to be kept when replacing the hose
Fuel Line Materials
Steel
Cheap and strong, but can cause leaks
Found it mainly front-wheel-drive and rear-wheel-drive vehicles
Rubber
Flexible and can be cut at needed length
Wear over time and can rub
Copper
Easy to fit and repair
Expensive and bulky
Found in mainly older vehicles
Plastic
Usually nylon
Don’t rust and are lighter
Melt at low temps and are harder to repair
Check Valve:
A valve with a check ball that covers the fuel line between the carburetor and the fuel tank.
When the system is working, the pressure of the vapor will move the ball and allow for vapor to flow to the tank.
If the vapor were to try to go back, the pressure would put the ball back in place and block the line to the carburetor.
Path Between Fuel Tank and Carburetor
The passage between the fuel tank and the carburetor has a separator between. It consists of a sealed can, a filter screen, an inlet fitting, an outlet fitting, and a metering outlet/orifice connecting to the tank.
The sealed can contains the filter screen that collects anything other than the vapor that travels.
The inlet fitting and outlet fittings both allow for the passage of vapor, but one goes to the tank and the other goes to the carburetor.
The metering orifice is connected to the tank and controls the amount that is released into the tank.
Vapor bubbles rise within the separator and is forced through the outlet pipe due to the pressure, which turns it into liquid.
Mounting and Fitting
Mounting
Fuel lines from tank to carburetor follow the frame of the underbody of the vehicle
Vapor and return lines are normally on the opposite frame rail, but sometimes are routed with the fuel lines
All rigid lines are fastened to the frame or underbody with screws and clamps or clips
Clamps are typically for fastening the hose to steel fuel lines
Fitting
Brass fittings are either flared or compression type
Flared is more common
Double flare is used while replacing a tube to prevent cracking and to ensure a good seal
Compression fittings have separate sleeves, tapered sleeve, or a half nut sleeve to make a good connection.
Various clamps are used to secure fuel hoses
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