* Ignition Switch: When the ignition is turned on, power flows to the fuel pump relay.
* Fuel Pump Relay: The relay acts as a switch, completing the circuit and sending power to the fuel pump. The ECM controls the relay's activation.
* ECM (Engine Control Module): The ECM monitors various engine parameters. It only activates the fuel pump relay when the engine needs fuel, typically after the engine crankshaft position sensor signals the engine is cranking. This prevents the pump from running unnecessarily when the engine is off.
* Inertia Switch: Many 1987 C10s also have an inertia switch (sometimes called a crash switch) which cuts power to the fuel pump in the event of a collision. This is a safety feature.
Troubleshooting No Power to the Fuel Pump:
To diagnose why your 1987 Chevy C10 fuel pump isn't getting power, you'll need to systematically check these components:
1. Check the Fuel Pump Relay: Locate the relay (usually in the underhood fuse box). You can swap it with another relay of the same amperage rating (to test if the relay is faulty) or check its continuity using a multimeter.
2. Check the Fuel Pump Fuse (if applicable): Some systems might have a separate fuse for the fuel pump circuit. Check your owner's manual or fuse box diagram.
3. Check the Inertia Switch: Locate the inertia switch (often under the dash or in the engine compartment). Reset it by pressing the button.
4. Check for Power at the Fuel Pump Relay: With the key ON, use a test light or multimeter to check for power at the relay's power input and output terminals. If power isn't getting to the input, trace the wiring back toward the ignition switch. If it's getting power to the input but not the output, the relay is likely faulty.
5. Check for power at the fuel pump itself: Connect a test light or multimeter to the fuel pump wiring. If there's no power at the pump with the ignition on, the problem lies between the relay and the pump (wiring, connections).
6. ECM Issues (Less Likely): Problems with the ECM are less likely to cause a complete lack of power to the fuel pump, but if other tests fail, it should be considered.
Important Note: Always disconnect the negative battery terminal before working on the electrical system to prevent accidental shorts. Consult a wiring diagram specific to your 1987 Chevy C10 model for the exact location of components and wiring routes.
