Automotive Systems

Formerly Automotive Systems I

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Fuel Lines And Hoses

Fuel Lines and Hoses

Fuel lines and hoses carry fuel from the tank to the engine. The main fuel line allows the fuel pump to draw fuel out of the tank. The fuel is pulled through this line to the pump and then to the carburetor, or metering section of the injection system.

Fuel lines are normally made of double wall steel tubing. For fire safety, a fuel line must be able to withstand the constant and severe vibration produced by the engine and road surface. Lines are placed away from exhaust pipes, mufflers, and manifolds, so that excessive heat will not cause vapor lock. They are attached to the frame, the engine, and other units, so the effects of vibration will be minimized. Fuel hoses, made of synthetic rubber, are used where severe movement occurs between parts. A flexible hose can absorb movement without breaking. Hose clamps are required to secure fuel hoses to the fuel lines or to metal fittings.

Faulty fuel lines and hoses are a common source of fuel leaks. Fuel hoses can become hard and brittle after being exposed to the engine heat and the elements. Engine oil can soften and swell them. Always inspect hoses closely and replace any in poor condition. Metal fuel lines rarely cause problems; however, they should be replaced if they become smashed, kinked, rusted, or leaking. Remember these rules when working with fuel lines and hoses:

  1. Place a rag around the fuel line fitting during removal. This action will keep fuel from spraying on you or on a hot engine. Use a flare nut or tubing wrench on fuel line fittings.
  2. Use only approved double wall steel tubing for fuel lines. never use copper or plastic tubing.
  3. Make smooth bends when forming a new fuel line. Use a bending spring or bending tool.
  4. Form double lap flares on the ends of fuel lines. A single lap flare is not approved for fuel lines.
  5. Reinstall fuel line hold-down clamps and brackets. If not properly supported, the fuel line can vibrate and fail.
  6. Route all fuel lines and hoses away from hot or moving parts. Double-check the clearance after installation.
  7. Only use approved synthetic rubber hoses in a fuel system. Vacuum hose is NOT to be used as fuel hose.
  8. Make sure fuel hoses completely cover its fitting or line before installing clamps. Pressure in the fuel system could force the hose off if not installed properly.
  9. Double-check all fitting for leaks. Start the engine and inspect the connections closely.


Most fuel injection systems have very high fuel pressure. Follow recommended procedures for bleeding or releasing pressure before disconnecting a fuel line or fitting. This action will prevent fuel spray from possibly causing injury or a fire.

Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

Copyright 2001-2004 SweetHaven Publishing Services
All rights reserved