GM 25163468 Fuel Pump

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To check the fuel pump output and pressure, relieve the fuel pressure. Next, Install a fuel pressure gauge on the fuel rail, location varies depending on the system. Turn the ignition switch on without starting the engine and note the reading on the gauge as the fuel pump runs for about two seconds. The pressure should hold steady within the specified range. Start the engine and let it idle at normal operating temperature, with the pressure expected to be lower by 3 to 10 psi. If the pressure does not drop as expected, apply a vacuum to the pressure regulator and if it drops, repair the vacuum source or replace the regulator. If the pressure is not within specifications, check for a vacuum to the regulator or a pinched/clogged fuel return hose. If the pressure is still low, change the fuel filter and if it remains low, install a fuel line shut-off adapter to test the regulator. If the pressure is still low with the return line restricted, there may be a leaking injector or a faulty fuel pump. To check the fuel pump's electrical circuits, verify that the pump runs by listening for a whirring noise when the ignition switch is turned on and when the engine is started.

To conduct a fuel pressure test, you'll need a fuel pressure gauge and appropriate adapter. First, ensure fuel is present and inspect for leaks. Attach the gauge to the fuel rail's Schrader valve, turn on the ignition, and observe the reading. Start the engine and check if the pressure drops by 3-10 psi. If not, apply vacuum to the regulator. If the pressure isn't correct, examine the fuel components. Afterward, release the pressure and remove the gauge. For Throttle Body Injection models, install the gauge between the fuel hose and throttle body. Using a jumper, observe the reading. If the pressure is off, inspect for restrictions or malfunctioning components. Finally, listen for the fuel pump's noise when starting. If it's silent, check the fuse and relay. Apply 12 volts to the pump's terminal to verify functionality. If it's non-operational, inspect the relay and pump circuit.

Apply vacuum to the pressure regulator and if it drops, repair the vacuum source or replace the regulator.

The fuel pump should be reassembled to the sending unit bracket assembly and then inserted back into the fuel tank.

The assembly can be released by carefully tapping the locking cam until the tabs align with the recesses.