For owners of 1973-1987 Chevy trucks, understanding the fuel line diagram is crucial for maintenance, repairs, or modifications, especially during engine swaps or upgrades. This guide provides a comprehensive overview of the fuel line routing for these classic vehicles, focusing on both single and dual tank setups.

Overview of Fuel Line Routing

The fuel system in the 73-87 Chevy trucks typically comprises a fuel tank, fuel pump, sending unit, and various lines connecting these components. The routing of these lines can vary depending on whether the truck has a single or dual tank setup.

Key Components

  • Fuel Tanks: These are available in various sizes and configurations. Ensure compatibility with your specific truck model.

  • Fuel Sending Units: These units monitor the fuel level and must match the tank's specifications.

  • Fuel Pumps: Depending on your engine type (e.g., LS swap), select a pump that meets the required pressure specifications (usually between 58-60 PSI for EFI systems).

Fuel Line Sizes

In general, the fuel lines are categorized by their diameter:

  • Supply Line: Typically 3/8 inch
  • Return Line: Usually 5/16 inch
  • Vent Line: Often 1/4 inch

Fuel Line Routing Instructions

Single Tank Setup

1. From Tank to Pump: The supply line (3/8 inch) runs from the tank to the fuel pump.

2. From Pump to Engine: The line continues from the pump directly to the engine's fuel rail.

3. Return Line: The return line (5/16 inch) goes from the engine back to the tank.

Dual Tank Setup

1. Tank Selection: Identify which tank is in use based on the fuel selector valve position.

2. Fuel Selector Valve: Connect both tanks to a fuel selector valve. The valve has multiple ports:

- Two ports for each tank’s supply lines (3/8 inch)

- Two ports for return lines (5/16 inch)

3. Routing Lines:

- Each tank's supply line connects to its respective port on the valve.

- The return lines from both tanks connect back to their respective ports on the valve.

4. Vent Lines: Ensure that vent lines are properly connected to prevent pressure build-up in the tanks.

ComponentLine Size
Supply Line3/8 inch
Return Line5/16 inch
Vent Line1/4 inch

Important Considerations

  • Compatibility: Always ensure that all components (tanks, pumps, sending units) are compatible with each other.

  • Pressure Requirements: For EFI conversions, ensure that your pump delivers adequate pressure and is installed correctly to avoid leaks.

  • Installation Tips: Secure all connections and consider using high-quality hoses to withstand increased pressure demands.

FAQs About Chevy Truck Fuel Lines

    • What size are the fuel lines on a 73-87 Chevy truck?
      The supply line is typically 3/8 inch, while the return line is usually 5/16 inch.

    • How do I know if my sending unit is compatible?
      Check that it matches your truck's tank specifications and has the correct ohm range.

    • Can I use a different fuel pump for an LS swap?
      Yes, but ensure it meets the required pressure specifications for your engine type.

Understanding these aspects of your Chevy truck's fuel system will aid in effective maintenance and upgrades. Whether performing routine checks or undertaking significant modifications, having a clear diagram and knowledge of your fuel lines is essential for success.