The fuel pump relay is typically located in the under-hood fuse/relay block on the driver’s side of the engine bay, and it is usually labeled “FUEL PUMP” or “PUMP” on the cover. If it isn’t in that block, some configurations place the relay in the interior fuse box behind the dash. Exact placement can vary by engine and options, so it’s worth checking both locations.
Where to look for the fuel pump relay
Understanding the most common spots helps you locate the relay quickly. The following locations are the ones you should inspect first.
- Under-hood fuse/relay center on the driver’s side of the engine bay, often mounted on the inner fender or near the firewall. Look for a relay labeled “FUEL PUMP” or something similar on the block cover.
- Interior fuse box behind the dash, typically on the passenger side kick panel or around the steering column. Check the cover labels for “FUEL PUMP” or “FUEL PUMP RELAY.”
- A smaller, secondary relay block that some early-model GM heavy trucks use, which may be mounted near the brake booster or along the inner fender. If you don’t find it in the main blocks, scan nearby mounting points in the engine bay and cab area.
If you can’t clearly identify the relay by label, you can trace the fuel pump wiring from the fuel tank. The relay will be in the circuit feeding power to the electric pump, often controlled by the ignition switch.
How to confirm you’ve found the right relay
Once you’ve located a candidate relay, confirm it is the fuel pump relay with these checks.
- Remove the relay and inspect the wiring diagram on the relay block cover or in the service manual to verify the FUEL PUMP designation.
- Use a multimeter or test light to verify there is power at the relay’s input terminal when the ignition is ON (and the engine may be cranking).
- With the ignition ON, but the engine not running, you should see voltage on the control circuit if the relay is being driven by the fuel pump relay coil (check coil resistance per service data).
- If permissible, temporarily jump the relay or power the pump directly (bypassing the relay) to see if the fuel pump runs, which helps confirm the relay’s function.
Note: Working around the fuel system can be dangerous. If you’re not confident with electrical diagnostics, consider consulting a qualified mechanic or the GM service manual for your exact VIN and engine configuration.
Additional tips for locating on different engine configurations
Because the 1997 GMC C6500 could be equipped with different engines (gasoline or diesel) and option packages, the relay’s exact placement can vary. Here’s how to approach variations safely.
- Gasoline-engined trucks commonly place the fuel pump relay in the under-hood fuse/relay center. Start your search there first.
- Some configurations route the fuel pump circuit through the interior fuse block. If you don’t find a match under the hood, inspect behind the dash area.
- Always consult the vehicle’s wiring diagram for your specific engine code and VIN to confirm the correct relay position.
If you’re still unable to locate the relay after checking these locations, acquiring the factory service manual or a reliable online wiring diagram for your exact chassis and engine will provide the definitive position.
Summary
For a 1997 GMC C6500, the fuel pump relay is most often found in the under-hood fuse/relay center on the driver’s side, labeled “FUEL PUMP.” If not there, check the interior fuse box behind the dash. Always verify with the vehicle’s wiring diagram for your exact engine and VIN, and exercise caution when testing electrical components around the fuel system. When in doubt, a professional mechanic can quickly identify and test the proper relay.