GMC 25117340 Fuel Pump

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If there is suspected insufficient fuel delivery, start by inspecting all fuel lines for leaks. Have an assistant turn the ignition switch to the ON position while listening for the fuel pump's "whirring" sound. If no sound is heard, check the fuel pump relay, fuses, and wiring. If power is present at the fuel pump connector and it still doesn't operate, replace the fuel pump. For the pressure check, use a fuel pressure gauge with the appropriate fittings. Relieve fuel pressure and install the gauge. Turn the ignition key On to observe the pressure reading, comparing it to the specified value. If the pressure is low, check for restrictions in fuel lines and filters, and inspect the fuel pump for issues. If the pressure is high, inspect the fuel return line for restrictions and replace the fuel pressure regulator if necessary. Start the engine and ensure the pressure is 3 to 10 psi below the previous reading. Monitor the pressure for five minutes after shutting off the engine; if it drops significantly, there might be a leak in the fuel line or injectors, or a defective fuel pump module check valve.

Insert the fuel pump/sending unit assembly into the fuel tank.

You can listen for the soft whirring sound of the fuel pump by sitting inside the vehicle with the windows closed and turning the ignition key to ON.

Start by inspecting all fuel lines for leaks.

To install the high-pressure fuel line, clean the fittings, apply oil to the threads, and install the new high-pressure fuel line.

Follow the reverse order of removal.

Before reinstalling the unit, you should inspect and clean the fuel pump inlet filter or strainer.

Inspect the condition of the seal around the mouth of the lockring mechanism. If it's dried out, cracked, or deteriorated, replace it. Also, inspect the strainer on the lower end of the fuel pump. If it's dirty, remove it, clean it with solvent, and blow it out with compressed air. If it's too dirty to be cleaned, it should be replaced. If the fuel pump and sending unit need to be separated, carefully pull the fuel pump into the rubber connector and slide the pump away from the bottom support. Take care not to damage the rubber insulator and fuel strainer during removal.