* Short Circuit in the Wiring Harness: This is the most common cause. A frayed wire, a wire chafing against metal, or corrosion in a connector anywhere in the fuel pump circuit can create a short, drawing excessive current and blowing the fuse. Inspect the wiring harness from the fuel pump all the way back to the fuse box, paying close attention to areas where the wires might rub against the chassis or other components.
* Faulty Fuel Pump Relay: The relay acts as a switch for the fuel pump. A bad relay can stick closed, causing a continuous draw of power and blowing the fuse. Testing the relay with a multimeter is essential to rule this out.
* Faulty Fuel Pump Motor: While less likely to *directly* blow the fuse, a failing fuel pump motor can draw significantly more current than normal as its windings wear down. This increased current draw can eventually overload the fuse. If the fuse keeps blowing even after checking the wiring and relay, the pump itself is suspect.
* Fuel Pump Wiring Connector: Corrosion or damage within the connector at the fuel pump itself can cause a short. Inspect this connector carefully for any signs of damage or corrosion. Clean the connector terminals with electrical contact cleaner if necessary.
* Incorrect Fuse Rating: Though less likely, make absolutely sure you are using the correct amperage fuse. Using a fuse with a lower rating than specified will cause it to blow. Check your owner's manual for the proper fuse rating.
* Something Stuck in the Fuel Pump: Less probable but possible. An object lodged within the pump could cause it to strain, drawing excess current.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine all wiring related to the fuel pump for any visible damage, fraying, or corrosion.
2. Relay Check: Test the fuel pump relay using a multimeter to ensure it's functioning correctly.
3. Fuse Check: Verify you're using the correct amperage fuse.
4. Wiring Continuity Test: Use a multimeter to check for continuity in the wiring harness to rule out any shorts.
5. Fuel Pump Current Draw Test: (Advanced) This requires more specialized tools but involves measuring the current draw of the fuel pump directly to see if it's excessively high.
If you're not comfortable working with car electrical systems, it's best to take your Pontiac Transport to a qualified mechanic for diagnosis and repair. Working with fuel system components can be dangerous.
