Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1991 Mercury Cougar LS, 3.8 4FACTORY OEM SERVICE PROCEDURE
Inertia Switch
- In event of a collision, electrical contacts in inertia switch open and fuel pump automatically shuts off. Fuel pump will shut off even if engine does not stop running. Engine will stop due to lack of fuel.
- Engine cannot be restarted until inertia switch is manually reset. To reset inertia switch, depress button on switch. Inertia switches may be found in the following locations:
- On Crown Victoria and Grand Marquis station wagon models, in the left rear side storage compartment.
- On RWD vehicles (except wagons), in trunk, on the left hinge support or behind trim panel.
- On Sable and Taurus, on left side of trunk (except station wagon).
- On Taurus and Sable station wagon models, behind access door in right rear cargo area.
- On all other vehicles, in trunk on left hinge support or behind trim panel.
CAUTION:
DO NOT reset inertia switch until fuel system has been inspected for leaks.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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