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 MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 5 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - EEC-IV)FUEL SYSTEMFUEL DELIVERYFUEL PRESSURE REGULATOR
1991 Mercury Tracer Base, 4D Sedan, Automatic
Fuel Pressure Regulator
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Fuel Pressure Regulator
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 1993 Mercury Tracer, 1993 Mercury Topaz, 1993 Mercury Sable, 1993 Mercury Grand Marquis, and 1993 Mercury Cougar. However, it is still accessible from the selected car via links, so may be relevant.
- Turn ignition off. Ensure vacuum hose is connected to fuel pressure regulator. Start and run engine for 10 seconds. Stop engine, and wait 10 seconds. Start and run engine for 10 seconds. Stop engine. Remove vacuum hose from pressure regulator. If fuel is present in vacuum port, replace fuel pressure regulator. If fuel is not present, go to step 2).CAUTION: Inspect fuel system for leaks and damage before testing fuel pump.
- Connect fuel pressure gauge to Schrader valve on fuel rail. Ground FP terminal at DLC. See Figure. Turn ignition on. Operate fuel pump for 30 seconds. Stop fuel pump, and check fuel pressure gauge. Ensure fuel pressure is within specification. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.Ensure pressure does not drop greater than 2 psi (.2 kg/cm2 ) in 3 minutes.
- If fuel pressure is within specification, fuel pressure regulator is okay and test is compete. If fuel pressure is not within specification, check fuel filter, and service as necessary. If fuel pressure is still not within specification, install vacuum gauge to intake manifold. Start engine, and observe vacuum and fuel pressure gauge while accelerating and decelerating engine.
- When engine is accelerating, vacuum reading should decrease and fuel system pressure should increase. When engine is decelerating, vacuum reading should increase and fuel system pressure should decrease. If readings are as indicated, fuel system is okay and test is compete.
- If gauge readings are not as indicated, turn ignition off. Disconnect and plug fuel pressure regulator hose. Attach vacuum pump to fuel pressure regulator. Start engine. Apply vacuum to pressure regulator while observing fuel pressure gauge. If fuel pressure changes as vacuum changes, repair restriction in vacuum supply hose. If fuel pressure does not change as vacuum changes, go to step 6).
- Ensure ignition is off. Relieve fuel pressure. Remove fuel pressure regulator. Check "O" ring, gasket and mounting surfaces for cracks, cuts and other damage. See Fig 1. Connect vacuum pump to fuel return tube. Apply 20 in. Hg. If maximum vacuum loss exceeds 10 in. Hg in 10 seconds, replace regulator. If maximum vacuum loss does not exceed 10 in. Hg in 10 seconds, recheck entire fuel delivery system for cause of fuel pressure loss.
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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.