Restoring a Mechanical Fuel Pump

Fuel pump repair/ restore is a serious matter but nothing too difficult for a beginner if a set of few important rules are followed. Mechanical fuel pumps are uncomplicated, generally stable and straightforward enough to overhaul.

How to restore a fuel pump?

• Removing a mechanical fuel pump starts with disconnecting the negative battery cable.
• The fuel tank hose at the fuel pump is detached, and the hose is plugged with a wooden dowel or bolt to keep the fuel from flowing out of wires.
• Then, check the hose and if it is cracked or ragged, replace it with a new fuel line.
• Disconnect the carburetor outlet line by using a wrench on the fuel pump and another over the line nut.
• The two attaching bolts are removed and the old fuel pump is pulled out. Clean away any material of the old gasket from the engine's mounting surface.
• Now, remove the top of the pump held by a central screw that holds the halves of the body together.
• Hold the halves together while removing the body screws. The pressure inside will force them apart.
• Make sure that you do not break open with a sharp metal object, which might scrape the mating surfaces and cause a leak.
• Freeing the diaphragm: As the lever is pulled out, a small spring will fall between the body and the lever. This keeps the lever resting against the cam when the pump is idling. The diaphragm stays down and the lever moves along up and down in the slot.

Cleaning and installation of the fuel pump

• Wash all the parts thoroughly with petrol and a fine brush. If possible replace the oil seal, diaphragm, valves, mounting gaskets and top gasket.
• Once the pump is apart and cleaned inside out, you will be able to inspect it for any damage as well as know how to detach the actuating links that operate the diaphragm.
• With the diaphragm taken out, check the seal under it and replace them if they show any signs of wear.
• Check the valve discs for any wear at the seat contact area and if there is any, turn over the disc to use the unworn side. Reassemble them with small springs and fiber washers.
• Now, check the seat where the sediment bowl fits by placing it in place with no gasket. Often the bowl seat will be distorted from the strain of the retaining device. If the distortion is much little, the use of a thicker gasket will correct the seal but if it is excess the seat must be flattened.
• Apply a coat of gasket sealer on either sides of the gasket. Put attaching bolts over the new pump and slip the gasket over the bolts.
• Install the new pump on the engine and make sure that the push rod is correctly equipped in both the fuel pump and the engine. If the push rod slides out, it can be packed with some grease to keep it in place while the pump is installed.
• Now, attach the fuel outlet line that runs into the carburetor. If it’s difficult to connect, detach the other end of the line from the carburetor. Connect the hose or line to the fuel pump, and then reattach the other end to the carburetor.
• Attach the fuel inlet hose and the vapor return hose. Tighten all the clamps well.
• Check the action of the pump and refit it to the vehicle and check for leaks.

This is a straight forward job and the only thing you should remember is that you are working with open fuel lines and need to be very careful.