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.
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HOMESERVICE MANUALSMERCURY1991COUGAR LS, 3.8 4REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTS - 3.8LFUEL SYSTEM TESTINGFUEL SYSTEM PRESSURE RELEASE
1991 Mercury Cougar LS, 3.8 4
Fuel System Pressure Release
1991 Mercury Cougar LS, 3.8 4SECTION Fuel System Pressure Release
- Remove fuel tank cap. Using Fuel Pressure Gauge (T80L-9974-B), release pressure from system at pressure relief valve (Schrader valve), located on fuel injection manifold rail.
- If fuel pressure gauge is not available, disconnect electrical connector to inertia switch located on left side of luggage compartment. Remove fuel cap to release fuel tank pressure. Crank engine for 15 seconds to reduce system pressure.
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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.