Download Fuel Injection Electronics Service - Goodheart

© Goodheart-Willcox Co., Inc.
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Chapter 28
Fuel and Emission Control
Systems Electronics Service
© Goodheart-Willcox Co., Inc.
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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.
© Goodheart-Willcox Co., Inc.
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Objectives
Summarize OBD II monitoring features
used on late-model fuel injection and
emission control systems.
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Fuel Injection Electronics Service
Fuel injection is controlled electronically
Electric fuel pumps
Sensors
Electronic control units
Fuel metering keeps each cylinder at
maximum efficiency
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Injection System Inspection
Check condition of all system
components
Look and smell for fuel leaks
Listen for vacuum leaks
Check terminals of wiring harness
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Fuel System On-Board Diagnostics
Self-diagnostic mode
Trouble codes in older systems
Compare to charts in service manual
Scan tool
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OBD II Fuel System Monitoring
Feedback from primary oxygen sensor
controls fuel mixture
Adjustments
Short term fuel trim
Long term fuel trim
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Injector Noid Light Test
Disconnect wiring
harness
Fit noid light into
harness connector
Start engine and
check light
Repeat on all
nonworking injectors
(OTC/SPX Corp.)
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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
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Injector Balance Test (Cont.)
Watch pressure gauge drop
Record pressure drop reading
Repeat for other injectors
Compare injector readings
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Injector Balance Test (Cont.)
(Chevrolet)
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Fuel System Wiring Diagrams
Show all components in circuit
Consult if you have difficulty finding
problem
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Review
In general, how can you tell if a
vacuum hose has a leak?
Answer: Listen for the characteristic “hiss.”
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Review
The temporary adjustment of injector
pulse width to correct the fuel mixture is
referred to as short term _____.
Answer: fuel trim
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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
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Injector Problems (Cont.)
Dirty injector
Lean air-fuel ratio
Poor spray pattern
Inadequate fuel delivery
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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
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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
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Replacing Multi-Point Injectors
(Cont.)
(Ford)
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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
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Fuel Tank Sending Unit Service
(Cont.)
(Honda Motor Co.)
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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
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Electric Fuel Pump Circuit Tests
Perform pressure
and volume tests
Measure voltage
to pump motor
(Honda Motor Co.)
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Fuel Pressure Sensor
Monitors fuel pressure
Measures fuel temperature
Read trouble code on scan tool
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Fuel Pump Shutoff Circuits
Inertia switch
Blocks fuel flow after impact
Oil pressure switch
Shuts off fuel pump if oil pressure is low
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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).
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Review
What type of switch is used to block
current flow to the electric fuel pump
after a collision?
Answer: inertia switch
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Emission Control System
Electronics Service
Defects in computer-controlled parts
EGR valve
Evaporative emission purge valve
Air injection
Other components
OBD II
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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
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OBD II Monitoring
Evaporative emissions system
EGR
Air injection system
Oxygen sensor
Catalyst monitor
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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
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Inspecting Emission Control
Systems
Inspect engine
vacuum hoses and
wires
Listening devices
Piece of vacuum hose
Stethoscope without
metal probe
(Snap-on Tool Corp.)
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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
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Vacuum Solenoid Service
Refer to vacuum
hose diagram
Check for
Hard, brittle hoses
Voltage to vacuum
Check solenoid
valve operation
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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
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Evaporative Emissions Control
System Service (Cont.)
(Honda Motor Co.)
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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
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Review
Which test measures the flow of fuel
vapors into the engine?
Answer: evaporative emissions system purge
test
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EGR System Electronic Service
EGR valve sticks open
Engine stalling at idle
Rough idle
EGR valve fails to open
Detonation
Knocking
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Electronic EGR System Testing
EGR valves trip trouble code
Use scan tool or refer to shop manual
Use oscilloscope to pinpoint trouble
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Electronic EGR System Testing
(Cont.)
(Fluke)
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Electric PCV Valve Service
New versions are electric
Older valves are spring loaded
Use scan tool to locate problems
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Testing the MAP Sensor
(Fluke)
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Testing the MAP Sensor (Cont.)
Digital MAP Signal
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(Fluke)
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Testing the MAP Sensor (Cont.)
Analog MAP Signal
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(Fluke)
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Oxygen Sensor Service
Check during engine
rev and deceleration
Lazy O2 sensor
Dead O2 sensor
Replace sensor at
periodic intervals
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Testing Oxygen Sensors
(Fluke)
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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
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Emissions Testing
Emissions testing program
Inspection and maintenance programs
Exact procedures vary from state to
state
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Review
What symptoms might indicate that an
EGR valve is stuck shut?
Answer: detonating or knocking
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Review
A(n) _____ oxygen sensor is one that
does not alter its output signal fast
enough to maintain an efficient air-fuel
ratio.
Answer: lazy
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