What does the inertia fuel shutoff switch do on the 4.9L Ford?

It is a safety device that shuts off (cuts) power to the electric fuel pump if a collision occurs; the switch opens on impact and must be reset manually.

What are the fuel gauge sender resistance values?

The sender is a variable resistor connected to a float in the fuel tank: 22.5 ohms when empty (low fuel) and 145 ohms when full (high fuel).

What wire feeds the Bronco fuel pump/fuel gauge sender?

Circuit 787, a PK/BK (pink/black) wire, runs from the inertia fuel shutoff through connector C441 to the fuel pump/fuel gauge sender. Ground is circuit 57 (BK) through splice S400 to G100.

How does the F-Series dual tank fuel pump wiring work?

Power from the inertia shutoff on circuit 670 (R/Y) goes to the fuel tank selector switch (page 49-2). The switch sends 12V on circuit 786 (R) via C440 to the front tank fuel pump/gauge sender, or circuit 789 (BR/W) via C205 and C441 to the rear tank sender.

What wire color and circuit feed the inertia fuel shutoff switch?

Circuit 238, a DG/Y (dark green/yellow) wire, carries 12V (relay energized) from C202 (page 23-1) through connector C271 to the inertia fuel shutoff.

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Ford 4.9L Fuel Pump & Sender Wiring Diagram - F-Series & Bronco (Page 23-7)

Engine Controls wiring diagram, 4.9L, page 23-7, inertia fuel shutoff and fuel pump circuits for F-Series and Bronco

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Ford 4.9L engine controls wiring diagram showing inertia fuel shutoff, fuel selector and fuel pump/gauge sender circuits for F-Series and Bronco.

AI caption August 2018 · Photo 364 of 386

This document is page 23-7 of a Ford engine controls wiring diagram set covering the 4.9L (300 cubic inch inline six) engine, showing the fuel pump and fuel gauge sender circuits for both F-Series trucks and the Bronco. Both circuits begin at connector C202 (referenced from page 23-1) with 12V on circuit 238 (DG/Y wire) feeding the Inertia Fuel Shutoff switch, a safety device that opens on impact to cut power to the electric fuel pump and must be reset manually. The F-Series side shows circuit 670 (R/Y) feeding a fuel tank selector switch (page 49-2), which routes power on circuit 786 (R) to the front tank fuel pump/gauge sender via C440, or circuit 789 (BR/W) to the rear tank sender via C441. The Bronco side uses circuit 787 (PK/BK) through C441 to a single fuel pump/fuel gauge sender, with circuit 29 (Y/W) tying in the instrument cluster (page 60-1). The sender is a variable resistor: 22.5 ohms empty, 145 ohms full. Both circuits ground on circuit 57 (BK) through splice S400 to ground G100 (grounds page 10-2 for F-Series, 10-5 for Bronco). Connector numbers, wire circuit numbers, and wire colors are given throughout.

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Frequently asked questions

What does the inertia fuel shutoff switch do on the 4.9L Ford?: It is a safety device that shuts off (cuts) power to the electric fuel pump if a collision occurs; the switch opens on impact and must be reset manually.
What are the fuel gauge sender resistance values?: The sender is a variable resistor connected to a float in the fuel tank: 22.5 ohms when empty (low fuel) and 145 ohms when full (high fuel).
What wire feeds the Bronco fuel pump/fuel gauge sender?: Circuit 787, a PK/BK (pink/black) wire, runs from the inertia fuel shutoff through connector C441 to the fuel pump/fuel gauge sender. Ground is circuit 57 (BK) through splice S400 to G100.
How does the F-Series dual tank fuel pump wiring work?: Power from the inertia shutoff on circuit 670 (R/Y) goes to the fuel tank selector switch (page 49-2). The switch sends 12V on circuit 786 (R) via C440 to the front tank fuel pump/gauge sender, or circuit 789 (BR/W) via C205 and C441 to the rear tank sender.
What wire color and circuit feed the inertia fuel shutoff switch?: Circuit 238, a DG/Y (dark green/yellow) wire, carries 12V (relay energized) from C202 (page 23-1) through connector C271 to the inertia fuel shutoff.