1. Check the fuses: The fuel pump is usually protected by a fuse in the underhood fuse box and possibly an additional fuse or relay inside the cab. Consult your owner's manual to locate the correct fuse(s) and relay(s) for the fuel pump. Check them visually for blown elements (a broken filament or melted metal). Replace any blown fuses with the correct amperage. If the fuse blows immediately upon replacement, you have a short circuit somewhere in the system and need to proceed cautiously.
2. Check the fuel pump relay: Locate the fuel pump relay (again, your owner's manual is crucial here). A simple test is to swap it with another relay of the same type (if possible, find one that controls a non-essential component). If the problem moves to the other component, you've found the faulty relay. Replace it with a new one.
3. Check the power at the fuel pump: This is the most important step. You'll need a test light or multimeter. With the ignition key ON (but not cranking the engine), disconnect the fuel pump wiring harness connector. Test for power at the connector's power wire (the owner's manual or a wiring diagram will help identify this wire). If there's no power, the problem lies before the fuel pump connector. If there *is* power, the problem is likely within the fuel pump itself or its wiring harness.
4. Check the inertia switch: Some vehicles have an inertia switch, a safety device that cuts power to the fuel pump in a collision. Locate this switch (usually under the dash or in the engine compartment) and check if it has tripped. Push the button to reset it (if applicable) and then test for power at the fuel pump again.
5. Check the wiring harness: Examine the wiring harness for any damage, chafing, or corrosion, especially near the fuel pump itself. Look for broken wires or loose connections. Repair or replace any damaged wiring.
6. Check the fuel pump's power wire: Trace the power wire from the fuel pump back to the fuse box. Look for any breaks, loose connections, or corrosion along its route.
7. Consider the PCM (Powertrain Control Module): In some cases, a faulty PCM can prevent power from reaching the fuel pump. This is less likely, but should be considered if all other checks are negative. Diagnosing a PCM problem generally requires specialized tools and knowledge.
Safety First: Work on the fuel system requires caution. Disconnect the negative battery terminal before beginning any work. Fuel is highly flammable, so keep sparks and open flames away.
If you're not comfortable performing these checks yourself, take your Blazer to a qualified mechanic. Incorrect diagnosis and repair can lead to further damage or even fire.
