Gasoline and Diesel Fuel Injection: Operation ... - Pearson Canada

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692 CHAPTER 29 Figure 29–39 Airflow through the positive crankcase ventilation (PCV) system. Note the closure hose at the front cam cover; blow-by gases may back-flow into the air intake under certain driving conditions, i.e., full-throttle, high RPM operation. (Courtesy Toyota Canada Inc.) (a) (b) Figure 29–40 (a) Dirty throttle plate. This throttle plate was so dirty that the technician removed the entire throttle body to be sure it was thoroughly cleaned. (b) Most throttle plates can be cleaned on the vehicle using a brush and throttle body cleaner. Be sure the cleaner is safe for oxygen sensors. Figure 29–41 Some vehicles, such as this Ford, have labels on the throttle body warning not to clean the throttle plates. A slippery coating is placed on the throttle plate and throttle bore that prevents deposits from sticking. Cleaning this type of housing can remove this protective coating.
Gasoline and Diesel Fuel Injection: Operation, Diagnosis, and Service 693 Figure 29–42 Schematic of a General Motors 2.8 litre gasoline fuel injection system with a mass airflow sensor. Many European and Asian vehicles use a cold-start fuel injector (as does this vehicle); however, cold-start injectors are not common in domestic vehicles, which typically use a major increase in injector pulse-width (“on” time) or a primer pulse (extra injector pulse) for cold engine starting. (Courtesy General Motors) this did not allow the precise control required to meet new standards. Electronic systems were introduced in the mid to late 1990s. We will start with conventional fuel injection. CONVENTIONAL (MECHANICAL) FUEL INJECTION Conventional fuel injection uses, for the most part, all mechanical components.There is limited electrical use. Other than glow-plug circuits, solenoids, block heaters, and fuel heaters, fuel delivery is governed by a mechanical injection pump. See Figure 29–44. Although here are variations between makes and engine types, the following is common with most systems. ■ Fuel tanks—Very similar to gasoline vehicles; multiple tanks are often used for long distance vehicles such as vans or pick-up trucks. The fuel supply line in the tank usually contains a prefilter to limit large contaminants from entering the system. ■ Lift pump—Transfers fuel from the fuel tank, through the fuel filter and on to the delivery system. This may be an electric pump or a mechanical pump driven by the engine. ■ Fuel filter—Very important with a diesel engine as any small particles or abrasives that get past the filter may cause damage to the injection pump or injectors. See Figure 29–45. Hand priming pumps are often found on the fuel filter; they are used to remove trapped air from the fuel system and to force fuel to the injection pump. Many late-model systems remove air automatically. ■ Water/fuel separators—Water in the fuel creates a number of driveability problems as well as system damage. Water is heavier than diesel fuel and will accumulate at the bottom of the separator, where it is drained as part of regular maintenance. Some separators have a sensor that illuminates a warning light on the instrument panel when the water reaches a given level. See Figure 29–46. Many late-model systems incorporate the fuel filter, water separator, and fuel heater in one unit.
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Gasoline and Diesel Fuel Injection: Operation ... - Pearson Canada

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