* Wiring Issues: This is the most likely culprit. Look for:
* Broken or frayed wires: Carefully inspect the wiring harness leading to the fuel pump. This harness is often subject to wear and tear, especially near the tank. Look for chafing against the chassis or other components.
* Corrosion: Check the connectors at both ends of the wiring harness for corrosion. Clean them with a wire brush and electrical contact cleaner.
* Loose Connections: Ensure all connections are secure. A loose connection can interrupt the power flow.
* Short Circuit: A short circuit anywhere in the wiring can blow a fuse, even after replacement, or prevent power from reaching the pump. This requires careful tracing of the wiring.
* Inertia Switch: Some vehicles have an inertia switch that cuts power to the fuel pump in the event of a collision to prevent fire. Locate this switch (usually under the dash or in the engine compartment) and check if it's tripped. There's usually a reset button.
* Fuel Pump Control Module (if equipped): Some vehicles have a fuel pump control module that acts as an intermediary between the main system and the pump itself. A faulty module could prevent power from reaching the pump, even with a good relay and fuses. This is less common but possible.
* Wiring at the Fuel Pump itself: Check the wiring connections directly at the fuel pump. Corrosion or damage here could be the problem.
* Ignition Switch: While less likely, a failing ignition switch could prevent power from reaching the fuel pump.
Troubleshooting Steps:
1. Obtain a Wiring Diagram: A wiring diagram for your specific 1993 Chevy Suburban is crucial. This will show you the exact path of the power wire to the fuel pump and allow you to systematically check each connection. You can usually find these online through repair manuals or forums dedicated to your vehicle.
2. Use a Voltmeter: With the key in the "ON" position (but not cranking the engine), use a voltmeter to test for power at various points along the wire leading to the fuel pump. Start at the fuse box, then trace the wire toward the pump, checking voltage at each connection point. This will pinpoint the location of the break in the circuit.
3. Check for Power at the Fuel Pump Connector: Connect your voltmeter directly to the fuel pump's wiring connector. If you don't have power here, the problem is before the connector. If you *do* have power, the problem is with the fuel pump itself.
4. Professional Help: If you are not comfortable working with automotive electrical systems, it's best to take your Suburban to a qualified mechanic. Incorrectly diagnosing and repairing electrical problems can be dangerous.
Remember safety first! Disconnect the battery's negative terminal before working on the electrical system to avoid accidental shorts and shocks.
