316 Auto Engine Repair Copyright by Goodheart-Willcox Co., Inc. 60% of emissions from engine exhaust 20% emissions from crankcase vapors 20% emissions from fuel evaporization Figure 15-16. These are the basic proportions of emissions produced by a vehicle. Note the high percentage from engine exhaust. Richer 14.7 to 1 Air-fuel ratio Leaner decrease NO x increasex HC and CO decrease HC and CO increase NO Figure 15-17. Generally, a rich mixture increases HC and CO emissions while decreasing NO X emissions. However, a lean mixture increases NO X emissions while decreasing HC and CO emissions. (General Motors) 2. Fit the correct noid light into the injector harness connector. 3. Start the engine and check the noid light. 4. If the noid light flashes, power is reaching the injector from the control module or control unit. If the noid light does not flash, something is preventing current from reaching the noid light, and thus the injector. There may be an open in the wiring, bad connection, open injector resistors, or control module troubles. 5. Repeat the noid light test on any injector that is not operating. Note: Refer to a wiring diagram when solving complex fuel injection electrical problems. The diagram shows all electrical connections and components that can upset the function of the injection system. Emission Control System Emission control systems are used to reduce the amount of harmful chemicals released into the atmosphere from a vehicle. This section of the chapter introduces the terminology, parts, and systems that control emissions. Emissions Emissions are chemicals emitted into the environment from various sources: • Volcanoes. • Decaying animal and vegetable matter. • Animal and human waste. • Other natural sources. • Vehicles. • Lawnmowers. • Power plants and factories. • Other man-made sources. Emissions from man-made sources must be controlled to maintain a balance in our environment. The four basic types of vehicle emissions are hydrocarbons, carbon monoxide, oxides of nitrogen, and particulates. Figure 15-16 shows the makeup of vehicle emissions: • Engine crankcase blowby fumes. • Fuel vapors. • Engine exhaust gases. Hydrocarbons (HC) Hydrocarbons (HC) result from the release of unburned fuel into the atmosphere. Hydrocarbon emis- sion can be caused by incomplete combustion or by fuel evaporation. For example, a rich mixture can result in increased HC levels because unburned fuel blows out of the combustion chamber and into the vehicle’s exhaust system. Look at Figure 15-17. HC levels in the atmosphere can also be increased by fuel vapors escaping from a vehicle’s fuel system. Hydrocarbon emissions can contribute to eye, throat, and lung irritation other illnesses and possibly cancer. Carbon Monoxide (CO) Carbon monoxide (CO) is an extremely toxic emission resulting from incomplete combustion. It is a colorless and odorless gas. CO poisoning can result in headaches, nausea, respiratory (breathing) problems, and death. CO prevents human blood cells from carrying oxygen to body tissues.