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 MANUALSMERCURY1994COUGAR 3.8 4, 4R70WREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTING - V8FUEL SYSTEMFUEL PRESSUREMODELS WITH EEC-V
1994 Mercury Cougar 3.8 4, 4R70W
Models With EEC-V
1994 Mercury Cougar 3.8 4, 4R70WSECTION Models With EEC-V
- Visually inspect fuel system including fuel lines, connections, injectors and electrical connections. Ensure Inertia Fuel Shutoff (IFS) switch is not tripped. Check condition of battery and fuses. Ensure fuel level in tank is sufficient.
- Turn ignition off. Release fuel pressure. Install fuel pressure gauge. Start engine and increase engine speed to 2500 RPM. If engine will not start, cycle ignition switch several times. Record fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS
article. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, proceed to appropriate SYSTEM/COMPONENT TESTS
article. Refer to the following menu:
- SYSTEM/COMPONENT TESTS - EEC-IV (5.0L) (for Mustang)
- SYSTEM/COMPONENT TESTS - EEC-V (for Cougar & Thunderbird 4.6L)
- SYSTEM/COMPONENT TESTS - EEC-IV (4.6L) (all other 4.6L)
- With fuel pressure gauge still installed, cycle ignition switch on and off several times. Record fuel pressure. If fuel pressure is at least 25 psi (172 kPa) after one minute with key off, system is capable of maintaining fuel pressure. If fuel pressure is not at least 25 psi after one minute with key off, test fuel injectors for leakage. See FUEL INJECTORS .
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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.