Thông tin tài liệu
OBJECTIVES After studying Chapter 26, the reader will be able to: Prepare for the ASE Engine Performance (A8) certification test content area “D” (Emission Control Systems) Describe the purpose and function of the evaporative emission control system Discuss how the evaporative emission control system is tested under OBD-II regulations Explain methods for diagnosing and testing faults in the evaporative emission control system Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 NEED FOR EVAPORATIVE EMISSION CONTROL • The purpose of the evaporative (EVAP) emission control system is to trap and hold gasoline vapors • The charcoal canister is part of an entire system of hoses and valves • Before the early 1970s, most gasoline fumes were simply vented to the atmosphere • The purpose of the EVAP system is to trap gasoline vapors —volatile organic compounds, or VOCs—that would otherwise escape into the atmosphere • These vapors are instead routed into a charcoal canister, from where they go to the intake airflow so they are burned in the engine Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 NEED FOR EVAPORATIVE EMISSION CONTROL Common Components • Most EVAP fuel tank filler caps have pressurevacuum relief built into them • When pressure or vacuum exceeds a calibrated value, the valve opens • Once the pressure or vacuum has been relieved, the valve closes FIGURE 26-1 A typical bayonet-type gas cap Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 VAPOR CANISTER STORAGE • The canister is located under the hood or underneath the vehicle, and is filled with activated charcoal granules that can hold up to one-third of their own weight in fuel vapors • A vent line connects the canister to the fuel tank FIGURE 26-2 Charcoal canister as mounted under the hood (Jeep) Not all charcoal canisters are this accessible; in fact, most are hidden under the hood or in other locations on the vehicle Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 VAPOR CANISTER STORAGE FIGURE 26-3 The evaporative emission control system includes all of the lines, hoses, and valves, plus the charcoal canister Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 VAPOR PURGING • During engine operation, stored vapors are drawn from the canister into the engine through a hose connected to the throttle body or the air cleaner • This “purging” process mixes HC vapors from the canister with the existing air-fuel charge Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 VAPOR PURGING Computer-Controlled Purge • Canister purging on engines with electronic fuel management systems is regulated by the powertrain control module (PCM) • Control of this function is particularly important because the additional fuel vapors sent through the purge line can upset the air–fuel ratio provided by a fuel-injection system • Since air–fuel ratio adjustments are made many times per second, it is critical that vapor purging is controlled just as precisely Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 VAPOR PURGING Computer-Controlled Purge FIGURE 26-4 A typical evaporative emission control system Note that when the computer turns on the canister purge solenoid valve, manifold vacuum draws any stored vapors from the canister into the engine Manifold vacuum also is applied to the pressure control valve When this valve opens, fumes from the fuel tank are drawn into the charcoal canister and eventually into the engine When the solenoid valve is turned off (or the engine stops and there is no manifold vacuum), the pressure control valve is spring-loaded shut to keep vapors inside the fuel tank from escaping to the atmosphere Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 EVAPORATIVE SYSTEM PRESSURE • Pressures can build inside the fuel system and are usually measured in units of inches of water, abbreviated in H2O (28 inches of water equals one PSI) • Pressure buildup is a function of: – – – – – – Fuel evaporation rates (volatility) Gas tank size (fuel surface area and volume) Fuel level (liquid versus vapor) Fuel slosh (driving conditions) Temperature (ambient, in-tank, close to the tank) Returned fuel from the rail Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ All of the following can increase the pressure in the evaporative emission control system except _ a) b) c) d) Fuel temperature Returned fuel from the fuel-injection system Inlet fuel to the fuel pump RVP of the fuel Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Evaporative emission control systems operate on low pressure measured in inches of water (in H2O) One PSI is equal to how many inches of water? a) b) c) d) 10 18 28 Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Evaporative emission control systems operate on low pressure measured in inches of water (in H2O) One PSI is equal to how many inches of water? a) b) c) d) 10 18 28 Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Inadequate purge flow rate will trigger which DTC? a) b) c) d) P0440 P0441 P0300 P0301 Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Inadequate purge flow rate will trigger which DTC? a) b) c) d) P0440 P0441 P0300 P0301 Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Two technicians are discussing a P0442 DTC Technician A says that it can be caused by a leaking EVAP line Technician B says that a leaking gas cap can cause a failure of the EVAP test Which technician is correct? a) b) c) d) Technician A only Technician B only Both Technicians A and B Neither Technician A nor B Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Two technicians are discussing a P0442 DTC Technician A says that it can be caused by a leaking EVAP line Technician B says that a leaking gas cap can cause a failure of the EVAP test Which technician is correct? a) b) c) d) Technician A only Technician B only Both Technicians A and B Neither Technician A nor B Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ A flow gauge is being used to check for proper canister pump flow rate What is the specification used by most emission test sites? a) b) c) d) 10 liters per minute liters per minute liter in minutes 0.5 liter per hour Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ A flow gauge is being used to check for proper canister pump flow rate What is the specification used by most emission test sites? a) b) c) d) 10 liters per minute liters per minute liter in minutes 0.5 liter per hour Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Before an evaporative emission monitor will run, the fuel level must be where? a) b) c) d) At least 75% full Over 25% Between 15% and 85% The level of the fuel in the tank is not needed to run the monitor test Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Before an evaporative emission monitor will run, the fuel level must be where? a) b) c) d) At least 75% full Over 25% Between 15% and 85% The level of the fuel in the tank is not needed to run the monitor test Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Technician A says that low pressure smoke installed in the fuel system can be used to check for leaks Technician B says that nitrogen under low pressure can be installed in the fuel system to check for leaks Which technician is correct? a) b) c) d) Technician A only Technician B only Both Technicians A and B Neither Technician A nor B Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Technician A says that low pressure smoke installed in the fuel system can be used to check for leaks Technician B says that nitrogen under low pressure can be installed in the fuel system to check for leaks Which technician is correct? a) b) c) d) Technician A only Technician B only Both Technicians A and B Neither Technician A nor B Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ 10 A large leak is detected by the evaporative emission control system monitor that could be caused by a loose gas cap Which DTC will likely be set? a) b) c) d) P0440 P0442 P0446 Either P0440 or P0442 Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ 10 A large leak is detected by the evaporative emission control system monitor that could be caused by a loose gas cap Which DTC will likely be set? a) b) c) d) P0440 P0442 P0446 Either P0440 or P0442 Automotive Fuel and Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 ... evaporative emission control system Discuss how the evaporative emission control system is tested under OBD-II regulations Explain methods for diagnosing and testing faults in the evaporative emission control. .. diagnose the evaporative emission control system? What are the parameters (enable criteria) that must be met for the evaporative system monitor to run? Automotive Fuel and Emissions Control Systems, ... Emissions Control Systems, 2/e By James D Halderman and Jim Linder © 2009 Pearson Higher Education, Inc Pearson Prentice Hall - Upper Saddle River, NJ 07458 CHAPTER QUIZ Evaporative emission control systems
Ngày đăng: 06/05/2018, 20:58
Xem thêm:
