GM 6472020 Fuel Pump Assembly

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The process for replacing a mechanical pump on carbureted models involves disconnecting the battery cable, detaching the fuel inlet hose, outlet line, and vapor return hose, removing the mounting bolts, and retrieving the pushrod. After cleaning the block mounting surface and applying grease to the pushrod, the new gasket and pump are installed and the hoses and lines are reattached. For electric pumps on fuel-injected models, the fuel system pressure is relieved and the fuel tank is removed. The fuel pump/sending unit assembly is unlocked by turning the inner ring counterclockwise, and then lifted from the tank. The rubber gasket and strainer are inspected and replaced if necessary. If needed, the fuel pump can be separated from the sending unit. The assembly is then inserted back into the fuel tank and the inner lock ring is turned clockwise to engage the locking cams. Finally, the fuel tank is installed.

To test the fuel pump, start by disconnecting the fuel line into the carburetor and then crank the engine.

The next steps involve detaching the fuel inlet hose, outlet line, and vapor return hose, removing the mounting bolts, and retrieving the pushrod.

To test the fuel pump relay, disconnect it and connect a test light to the ignition wire. When the key is turned on, the test light should come on for a few seconds and then turn off. Use a jumper wire to connect the ignition wire to the fuel pump wire on the relay connector and check if the fuel pump activates. To check the fuel pump pressure, relieve the fuel system pressure and attach a fuel pressure gauge to the appropriate location. Turn the ignition key to on and check the fuel pressure on the gauge. If the pressure is low, the fuel pressure regulator may be defective. If the pressure is too high, check for a restricted fuel line or a defective regulator.

The rubber gasket and strainer should be inspected and replaced if necessary.

To test the fuel pump relay, disconnect it and connect a test light to the ignition wire. When the key is turned on, the test light should come on for a few seconds and then turn off. Use a jumper wire to connect the ignition wire to the fuel pump wire on the relay connector and check if the fuel pump activates. To check the fuel pump pressure, relieve the fuel system pressure and attach a fuel pressure gauge to the appropriate location. Turn the ignition key to on and check the fuel pressure on the gauge. If the pressure is low, the fuel pressure regulator may be defective. If the pressure is too high, check for a restricted fuel line or a defective regulator.