GM 6471599 FUEL PUMP

For carbureted engines, ensure sufficient fuel, inspect fuel lines for leaks or damage, and test for a strong gasoline spurt when cranking the engine. If weak, assess the fuel pump and its flow capacity; it should pump a pint in 30 seconds. For fuel-injected engines, listen for the pump's whirring noise on ignition. If silent, inspect the fuse, relay, and circuit. To test the pump, apply battery voltage to its gray wire terminal. To verify the relay, use a test light and jumper wire. If there's an issue with fuel pressure, connect a gauge and check when the ignition is on. Low pressure might indicate a defective regulator, and high pressure could signify a blockage or faulty regulator. On MPFI models, check the regulator's function by observing pressure changes when detaching its vacuum hose.

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.

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