1991 1999 ford explorer chilton User Manual
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SPECIFICATION CHARTS IAT and ECT sensor specifications chartClick to enlarge Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. SPECIFICATION CHARTS 599
BASIC FUEL SYSTEM DIAGNOSIS When there is a problem starting or driving a vehicle, two of the most important checks involve the ignition and the fuel systems. The questions most mechanics attempt to answer first, is there spark? and is there fuel? will often lead to solving most basic problems. For ignition system diagnosis and testing, please refer to the information on engine electrical components and ignition systems found earlier in this manual. If the ignition system checks out (there is spark), then you must determine if the fuel system is operating properly (is there fuel?). Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. BASIC FUEL SYSTEM DIAGNOSIS 601
FUEL LINES AND FITTINGS General Information Quick-connect (push type) fuel line fittings must be disconnected using proper procedure or the fitting may be damaged. There are two types of retainers used on the push connect fittings. Line sizes of 3 /8 and 5 /16 in. diameter use a hairpin clip retainer. The 1 /4 in. diameter line connectors use a duck-bill clip retainer. In addition, some engines use spring-lock connections, secured by a garter spring, which require Ford Tool T81P-19623-G (or equivalent) for removal. Hairpin Clip Fitting REMOVAL & INSTALLATION Clean all dirt and grease from the fitting. Spread the two clip legs about 1 /8 in. (3mm) each to disengage from the fitting and pull the clip outward from the fitting. Use finger pressure only; do not use any tools. 1. Grasp the fitting and hose assembly and pull away from the steel line. Twist the fitting and hose assembly slightly while pulling, if the assembly sticks. 2. Inspect the hairpin clip for damage, replacing the clip if necessary. Reinstall the clip in position on the fitting. 3. Inspect the fitting and inside of the connector to ensure freedom from dirt or obstruction. Install the fitting into the connector and push together. A click will be heard when the hairpin snaps into the proper connection. Pull on the line to insure full engagement. 4. FUEL LINES AND FITTINGS 603
Hairpin clip fuel fitting installation Click to enlarge HOW TO USE THIS BOOK 604 REMOVAL & INSTALLATION
Exploded views of the hairpin and duckbill clip type fuel fittings Click to enlarge Duckbill Clip Fitting REMOVAL & INSTALLATION A special tool is available from Ford and other manufacturers for removing the retaining clips. Use Ford Tool T82L-9300-AH or equivalent. If the tool is not on hand, go onto step 2. Align the slot on the push connector disconnect tool with either tab on the retaining clip. Pull the line from the connector. 1. If the special clip tool is not available, use a pair of narrow 6-inch slip-jaw pliers with a jaw width of 0.2 in (3mm) or less. Align the jaws of the pliers with the openings of the fitting case and compress the part of the retaining clip that engages the case. Compressing the retaining clip will release the fitting, which may be pulled from the connector. Both sides of the clip must be compressed at the same time to disengage. 2. Inspect the retaining clip, fitting end and connector. Replace the clip if any damage is apparent. 3. Push the line into the steel connector until a click is heard, indicating the clip is in place. Pull on the line to check engagement. 4. HOW TO USE THIS BOOK Duckbill Clip Fitting 605
Duckbill clip fuel fitting installation Click to enlarge Spring Lock Coupling HOW TO USE THIS BOOK 606 REMOVAL & INSTALLATION
REMOVAL & INSTALLATION The spring lock coupling is held together by a garter spring inside a circular cage. When the coupling is connected together, the flared end of the female fitting slips behind the garter spring inside the cage of the male fitting. The garter spring and cage then prevent the flared end of the female fitting from pulling out of the cage. As an additional locking feature, most vehicles have a horseshoe-shaped retaining clip that improves the retaining reliability of the spring lock coupling. Spring lock fitting removal and installation proceduresClick to enlarge HOW TO USE THIS BOOK REMOVAL & INSTALLATION 607
Spring lock horseshoe-shaped retaining clip installation Click to enlarge Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. HOW TO USE THIS BOOK 608 REMOVAL & INSTALLATION
SEQUENTIAL FUEL INJECTION (SFI) SYSTEM General Information The Sequential Fuel Injection (SFI) system includes a high pressure, inline electric fuel pump mounted in the fuel tank, a fuel supply manifold, a throttle body (meters the incoming air charge for the correct mixture with the fuel), a pressure regulator, fuel filters and both solid and flexible fuel lines. The fuel supply manifold includes 4, 6 or 8 electronically-controlled fuel injectors, each mounted directly above an intake port in the lower intake manifold. Each injector fires once every other crankshaft revolution, in sequence with the engine firing order. The fuel pressure regulator maintains a constant pressure drop across the injector nozzles. The regulator is referenced to intake manifold vacuum and is connected in parallel to the fuel injectors; it is positioned on the far end of the fuel rail. Any excess fuel supplied by the fuel pump passes through the regulator and is returned to the fuel tank via a return line. The pressure regulator reduces fuel pressure to 39-40 psi under normal operating conditions. At idle or high manifold vacuum condition, fuel pressure is further reduced to approximately 30 psi. The fuel pressure regulator is a diaphragm-operated relief valve, in which the inside of the diaphragm senses fuel pressure and the other side senses manifold vacuum. Normal fuel pressure is established by a spring preload applied to the diaphragm. Control of the fuel system is maintained through the Powertrain Control Module (PCM), although electrical power is routed through the fuel pump relay and an inertia switch. The fuel pump relay is normally located in the power distribution box, under the hood, and the inertia switch is located on the toe-board, to the right of the transmission hump, in the passenger-side footwell. The inline fuel pump is usually mounted in the fuel tank. Tank-mounted pumps can be either high- or low-pressure, depending on the model. The inertia switch opens the power circuit to the fuel pump in the event of a collision. Once tripped, the switch must be reset manually by pushing the reset button on the assembly. Check that the inertia switch is reset before diagnosing power supply problems to the fuel pump. The fuel injectors used with SFI system are electro-mechanical (solenoid) type, designed to meter and atomize fuel delivered to the intake ports of the engine. The injectors are mounted in the lower intake manifold and positioned so that their spray nozzles direct the fuel charge in front of the intake valves. The injector body consists of a solenoid-actuated pintle and needle-valve assembly. The control unit sends an electrical impulse that activates the solenoid, causing the pintle to move inward off the seat and allow the fuel to flow. The amount of fuel delivered is controlled by the length of time the injector is energized (pulse width), since the fuel flow orifice is fixed and the fuel pressure drop across the injector tip is constant. Correct atomization is achieved by contouring the pintle at the point where the fuel enters the pintle chamber. Exercise care when handling fuel injectors during service. Be careful not to lose the pintle cap and always replace O-rings to assure a tight seal. Never apply direct battery voltage to test a fuel injector. The injectors receive high-pressure fuel from the fuel supply manifold (fuel rail) assembly. The complete assembly includes a single, pre-formed tube with four, six or eight connectors, the mounting flange for the pressure regulator, mounting attachments to locate the manifold and provide the fuel injector retainers and a Schrader® quick-disconnect fitting used to perform fuel pressure tests. The fuel manifold is normally removed with the fuel injectors and pressure regulator attached. Fuel injector electrical connectors are plastic and have locking tabs that must be released when disconnecting the wiring SEQUENTIAL FUEL INJECTION (SFI) SYSTEM 609
harness. FUEL SYSTEM SERVICE PRECAUTIONS Safety is the most important factor when performing not only fuel system maintenance, but any type of maintenance. Failure to conduct maintenance and repairs in a safe manner may result in serious personal injury or death. Work on a vehicles fuel system components can be accomplished safely and effectively by adhering to the following rules and guidelines. To avoid the possibility of fire and personal injury, always disconnect the negative battery cable unless the repair or test procedure requires that battery voltage by applied. · Always relieve the fuel system pressure prior to disconnecting any fuel system component (injector, fuel rail, pressure regulator, etc.) fitting or fuel line connection. Exercise extreme caution whenever relieving fuel system pressure to avoid exposing skin, face and eyes to fuel spray. Please be advised that fuel under pressure may penetrate the skin or any part of the body that it contacts. · Always place a shop towel or cloth around the fitting or connection prior to loosening to absorb any excess fuel due to spillage. Ensure that all fuel spillage is quickly remove from engine surfaces. Ensure that all fuel-soaked cloths or towels are deposited into a flame-proof waste container with a lid. · Always keep a dry chemical (Class B) fire extinguisher near the work area. · Do not allow fuel spray or fuel vapors to come into contact with a spark or open flame. · Always use a second wrench when loosening or tightening fuel line connections fittings. This will prevent unnecessary stress and torsion to fuel piping. Always follow the proper torque specifications. · Always replace worn fuel fitting O-rings with new ones. Do not substitute fuel hose where rigid pipe is installed. · Relieving Fuel System Pressure All SFI fuel injected engines are equipped with a pressure relief valve located on the fuel supply manifold. Remove the fuel tank cap and attach fuel pressure gauge T80L-9974-B, or equivalent, to the valve to release the fuel pressure. Be sure to drain the fuel into a suitable container and to avoid gasoline spillage. If a pressure gauge is not available, disconnect the vacuum hose from the fuel pressure regulator and attach a hand-held vacuum pump. Apply about 25 in. Hg (84 kPa) of vacuum to the regulator to vent the fuel system pressure into the fuel tank through the fuel return hose. Note that this procedure will remove the fuel pressure from the lines, but not the fuel. Take precautions to avoid the risk of fire and use clean rags to soak up any spilled fuel when the lines are disconnected. An alternate method of relieving the fuel system pressure involves disconnecting the inertia switch. Follow the procedures outlined later in this Section. HOW TO USE THIS BOOK 610 General Information