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Chapter 28

Chapter 28. Fuel and Emission Control Systems Electronics Service. Objectives. Recall the tasks involved in a preliminary inspection of the injection system. Test electrical/electronic components found on late-model fuel and emission control systems.

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Chapter 28

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  1. Chapter 28 Fuel and Emission Control Systems Electronics Service

  2. Objectives • Recall the tasks involved in a preliminary inspection of the injection system. • Test electrical/electronic components found on late-model fuel and emission control systems. • Use a fuel system wiring diagram to locate all the components in the circuit that could be causing problems.

  3. Objectives • Summarize OBD II monitoring features used on late-model fuel injection and emission control systems.

  4. Fuel Injection Electronics Service Fuel injection is controlled electronically Electric fuel pumps Sensors Electronic control units Fuel metering keeps each cylinder at maximum efficiency

  5. Injection System Inspection Check condition of all system components Look and smell for fuel leaks Listen for vacuum leaks Check terminals of wiring harness

  6. Fuel System On-Board Diagnostics • Self-diagnostic mode • Trouble codes in older systems • Compare to charts in service manual • Scan tool

  7. OBD II Fuel System Monitoring Feedback from primary oxygen sensor controls fuel mixture Adjustments Short term fuel trim Long term fuel trim

  8. Injector Noid LightTest Disconnect wiring harness Fit noid light into harness connector Start engine and check light Repeat on all nonworking injectors (OTC/SPX Corp.)

  9. Injector Balance Test Connect pressure gauge to test fitting Close fuel volume measurement valve Connect balance tester to injector Turn ignition key on to pressurize system Turn ignition key off Press tester button

  10. Injector Balance Test (Cont.) Watch pressure gauge drop Record pressure drop reading Repeat for other injectors Compare injector readings

  11. Injector Balance Test (Cont.) (Chevrolet)

  12. Fuel System Wiring Diagrams Show all components in circuit Consult if you have difficulty finding problem

  13. Review In general, how can you tell if a vacuum hose has a leak? Answer: Listen for the characteristic “hiss.”

  14. Review The temporary adjustment of injector pulse width to correct the fuel mixture is referred to as short term _____. Answer: fuel trim

  15. Injector Problems Bad injector Shorted or open coil windings Injector or engine misfire trouble code Leaking injector Worn or dirty injector Weak or broken return spring

  16. Injector Problems (Cont.) Dirty injector Lean air-fuel ratio Poor spray pattern Inadequate fuel delivery

  17. Servicing EFI Injectors Check with stethoscope Check coil condition (engine off) Measure resistance across injector coil Check wiring to injector Check supply voltage to injector

  18. Replacing Multi-Point Injectors Bleed off fuel system pressure Remove hose from injector and fuel rail Unplug electrical connection Remove injector Inspect rubber parts Replace injector and rubber parts, if necessary

  19. Replacing Multi-Point Injectors (Cont.) (Ford)

  20. Fuel Tank Sending Unit Service Test fuel gauge before sending unit Use ohmmeter to test sending unit For further testing, remove sending unit Measure resistance Check float for leakage

  21. Fuel Tank Sending Unit Service (Cont.) (Honda Motor Co.)

  22. Fuel Pump Service Low fuel pump pressure Worn pump bearings High resistance in pump circuit Leaking check valves High fuel pump pressure Inoperative pressure relief valve Faulty fuel pressure regulator

  23. Perform pressure and volume tests Measure voltage to pump motor Electric Fuel Pump Circuit Tests (Honda Motor Co.)

  24. Fuel Pressure Sensor Monitors fuel pressure Measures fuel temperature Read trouble code on scan tool

  25. Fuel Pump Shutoff Circuits Inertia switch Blocks fuel flow after impact Oil pressure switch Shuts off fuel pump if oil pressure is low

  26. Review While using a stethoscope to check an EFI injector, you hear a clicking sound. What does this mean? Answer: The injector is working (opening and closing).

  27. Review What type of switch is used to block current flow to the electric fuel pump after a collision? Answer: inertia switch

  28. Emission Control System Electronics Service Defects in computer-controlled parts EGR valve Evaporative emission purge valve Air injection Other components OBD II

  29. Emission Maintenance Reminder Dash light reminder for emission control service Must be deactivated after adjustments and repairs are done Numerous methods Refer to service manual

  30. OBD II Monitoring Evaporative emissions system EGR Air injection system Oxygen sensor Catalyst monitor

  31. Emission System Scanning Scan tool monitoring of various emission control systems Connect scan tool Check for stored trouble codes Think about what could cause codes

  32. Inspecting Emission Control Systems Inspect engine vacuum hoses and wires Listening devices Piece of vacuum hose Stethoscope without metal probe (Snap-on Tool Corp.)

  33. Inspecting Emission Control Systems (Cont.) Look for oil leaks onto oxygen sensor Check for dirty engine oil and blowby Inspect air cleaner Check adjustment of air pump belt

  34. Vacuum Solenoid Service Refer to vacuum hose diagram Check for Hard, brittle hoses Voltage to vacuum Check solenoid valve operation

  35. Evaporative Emissions Control System Service Evaporative emissions system purge test Evaporative emissions system pressure test Evaporative emissions control system maintenance Replace filter Inspect fuel tank filler cap and hoses

  36. Evaporative Emissions Control System Service (Cont.) (Honda Motor Co.)

  37. Review Another name for the secondary oxygen sensor is _____. A. elemental sensor B. catalyst monitor C. front sensor D. primary sensor Answer: B. catalyst monitor

  38. Review Which test measures the flow of fuel vapors into the engine? Answer: evaporative emissions system purge test

  39. EGR System Electronic Service EGR valve sticks open Engine stalling at idle Rough idle EGR valve fails to open Detonation Knocking

  40. Electronic EGR System Testing EGR valves trip trouble code Use scan tool or refer to shop manual Use oscilloscope to pinpoint trouble

  41. Electronic EGR System Testing (Cont.) (Fluke)

  42. Electric PCV Valve Service New versions are electric Older valves are spring loaded Use scan tool to locate problems

  43. Testing the MAP Sensor (Fluke)

  44. Testing the MAP Sensor (Cont.) Digital MAP Signal (Fluke)

  45. Testing the MAP Sensor (Cont.) Analog MAP Signal (Fluke)

  46. Oxygen Sensor Service Check during engine rev and deceleration Lazy O2 sensor Dead O2 sensor Replace sensor at periodic intervals

  47. Testing Oxygen Sensors (Fluke)

  48. Testing Wide Band Oxygen Sensors Also called air-fuel ratio sensor 3.3 volts is normal Other voltages result in trouble code Scan tool Oxygen sensor signal generator

  49. Emissions Testing Emissions testing program Inspection and maintenance programs Exact procedures vary from state to state

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