Airtex 40503 Mechanical Fuel Pump

Mechanical fuel pump for classic GM applications

Airtex 40503 is a mechanical fuel pump for specific carbureted and non-fuel-injected vehicles. It is built for external mounting and uses a hose connection inlet with a threaded outlet for the listed applications.

Key features

• Meets or exceeds OEM specifications for fit and performance.
• Precision castings and hardened rockers support long service life.
• Advanced polymer diaphragms help maintain consistent fuel delivery across multiple fuel blends.
• Factory tested throughout manufacturing for verified operation.
• Includes a gasket or seal for installation on the specified application.

Detailed description

This Airtex mechanical fuel pump is engineered for classic Chevrolet and GMC vehicles that use a 2 line pump setup. Compatible applications include Chevrolet C10 Pickup, Chevrolet Chevelle, GMC C15/C1500 Pickup, and Chevrolet Impala among many other listed models. The 40503 part number is associated with a specific-fit replacement, making it a practical choice when restoring fuel delivery on older GM platforms. This part cross-references Carter M4513 for the same application.

What it is used for

• Restoring fuel pressure in a mechanical fuel system.
• Replacing a worn pump that causes hard starting.
• Addressing fuel starvation under normal engine operation.
• Correcting inconsistent delivery in carbureted applications.
• Replacing a leaking pump on a classic GM vehicle.

Installation notes and tips

Verify the vehicle uses a 2 line pump before ordering. The pump has one inlet and one outlet, with a 5/16 inch inlet thread size and a 1/2-20 UNF outlet thread size. Airtex recommends replacing the fuel filter when servicing the pump. Mounting hardware is not included.

Quality assurance

Airtex states that this pump is 100% tested during the manufacturing process to support out-of-the-box operation. The 40503 is built to meet or exceed OEM specifications for fit and performance.