Chapter 15 Fuel and Emission Control Systems 309 Copyright by Goodheart-Willcox Co., Inc. Fuel rail High-pressure line Fuel inlet line Piston Engine control module Direct injector Cam eccentric (lobe) Figure 15-4. The mechanical fuel pumps used in late-model direct injection systems are driven by an eccentric lobe on the engine camshaft. (Bosch) Air cleaner cap Air filter Air cleaner case Intake air connector pipe Air cleaner inlet Resonator Resonator Tuning hole Under Side View Figure 15-5. The air filter mounts inside a metal or plastic housing. (Honda) • Seal off the fuel lines when the pump is removed to prevent leakage and a potential fire. • Make sure you have correct replacement pump. Match up the new pump with the old one. • Tighten hose clamps, fittings, and fasteners properly. • Check for fuel leaks before releasing the vehicle to the customer. Air Supply System The air supply system removes dust and dirt from the air entering engine intake manifold. An air filter traps the particles. The air filter fits inside a metal or plastic housing, Figure 15-5. Most air filters have a paper element. A few vehicles use a polyurethane foam element. Fuel Metering System The fuel supply system provides fuel to the fuel meter- ing system. The fuel metering system controls amount of fuel that is mixed with the filtered air. The fuel metering system may be throttle body injection or multiport injection. The next section discusses the fuel metering system in detail. Fuel Metering System Modern gasoline injection systems use engine sensors, a computer, and solenoid-operated fuel injectors to meter the correct amount of fuel into the engine. Termed electronic fuel injection (EFI), these systems use electric and electronic devices to monitor and control engine operation. An electronic control module (ECM), or com- puter, receives electrical signals from the various sensors. The ECM processes this data and operates the injectors, ignition system, and other engine related devices. Throttle Body, Multiport, and Direct Injection The three types of electronic fuel injection are mul- tiport, throttle body, and direct injection. In throttle body injection, one or two injectors are mounted inside a throttle body assembly. Fuel is sprayed into one point or location at the center inlet of the engine intake mani- fold. In multiport injection, or port fuel injection, one injector is located just before each intake port. Fuel is injected into the engine in more than one location. Direct injection systems spray fuel directly into the combustion chambers, Figure 15- 6. Gasoline Injection Components The basic parts of a fuel injection system are: • Fuel rail. This is a metal tube or casting that feeds fuel to the fuel pressure regulator and injectors, Figure 15-7. It usually has a service fitting. • Fuel pressure regulator. A diaphragm-operated pres- sure-relief valve that maintains a constant pressure at the injectors, Figure 15-8.