© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 27 Ignition System Diagnosis and Service

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Always turn the ignition switch off before disconnecting any system wiring Do not touch any exposed connections while the engine is running or cranking Ignition System Service Precautions

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Misfires Something that prevents complete combustion

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Misfires (Cont.) Can cause lack of power, poor fuel mileage, excessive emissions, and rough running Ignition misfires can be caused by weak spark, fouled plug, faulty coil, primary or secondary faults, or incorrect plug gap

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Excessively advanced ignition timing Engine overheating Excessively lean mixtures Gasoline with too low octane rating Abnormal Combustion - Detonation

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Detonation

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Preignition Can cause pinging or spark knock Any hot spot within the combustion chamber can cause preignition Common causes include incandescent carbon deposits, faulty cooling system, too hot of a spark plug, poor lubrication, and cross firing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Preignition

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Common – Problems affect all cylinders – Components include parts of the primary circuit and secondary circuit up to the distributor rotor Uncommon – Problems affect one or more but not all cylinders – Components include plug wires and plugs Types of Ignition System Problems

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Visual Inspection No-start conditions mostly caused by primary circuit faults Common symptoms of ignition problems include: – Hard starting – Rough idle – Engine stalling

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Visual Inspection

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Common Symptoms (Cont.) Hesitation Stumble Poor acceleration Surge Bucking Knocking Backfire

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Scan Tools Check MIL, DTCs, and freeze frame data. Look for TSBs If no DTCs, look at serial data Check monitor status Monitor input data If no problems are present in on-board system, proceed with symptom diagnosis

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Mode 6 Data

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Primary Circuit Inspect wiring and connections Perform wiggle test Examine ignition switch Check charging system and battery Inspect for moisture affecting wiring

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Ground Circuits Misplaced or unconnected ground straps can force an alternate path to ground Voltage drop test ignition module ground Poor sensor grounds can cause the same symptoms as a faulty sensor

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electromagnetic Interference EMI can cause on-board computer problems Can alter signals Route sensor wiring away from EMI sources Ignition coil, plug wires, and AC generator can produce EMI

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Sensors Inspect magnetic pulse generators and Hall- effect sensors and wiring The non-magnetic reluctor can become magnetized and affect pulse generator signal

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Control Modules Use transistors as switches Modules can be mounted in distributor, remotely, or as part of PCM Check for clean and tight mounting May require heat-conductive silicone grease on mounting surface

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Secondary Circuit Inspect plug wires and boots for damage Ensure correct wire routing Check coil(s) for cracks Inspect cap and rotor

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Visual inspection: – Check for loose or corroded connections – Look for signs of moisture Check DTCs Check fuel system operation Check engine mechanical condition No-Start Diagnosis

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Basic No-Start Diagnosis Test spark at spark plug – If no spark, test at coil output terminal Check for voltage at coil negative terminal Crank engine and check for coil pulse – If no pulse, problem is with control module or pickup

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Checking Coil Pulse

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. No-Start Diagnosis of EI System Determine whether problem is ignition related by using a spark tester Check for voltage at each coil’s primary circuit Check crankshaft sensor output with a voltmeter or oscilloscope

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Technician A says a faulty ignition module can cause a no-start condition. Technician B says a faulty coil can cause a no-start condition. Who is correct?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cylinder performance test Battery, starting, and charging test Emission level analysis Engine computer system diagnosis Ignition performance test Diagnosis with an Engine Analyzer

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Also called a power balance or contribution test Each cylinder is tested Spark or fuel is stopped and the RPM drop is recorded A weak cylinder will have little RPM drop Cylinder Performance Test

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Power Balance Testing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Ignition Performance Tests Most analyzers include primary and secondary tests: – Kilovolt (KV) tests – Acceleration (snap) tests – Cylinder burn time – Display patterns

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Scope Patterns Oscilloscopes connect to: – Primary circuit at coil negative terminal – Ground – Secondary lead pick-up – Number one cylinder

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Understanding Single Cylinder Patterns

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Firing Line – Represents the voltage needed to overcome the resistance in the secondary circuit Spark Line – Represents the time the spark lasts Intermediate or Coil Section – Shows the remaining coil oscillations Dwell Section – Shows the length of time current is flowing through the primary circuit Ignition Pattern Components

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Typical Secondary Pattern

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Pattern Display Modes Display Pattern – All cylinders from left to right Raster Pattern – Stacks waveforms above each other Superimposed Pattern – Places all waveforms on top of each other

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Spark Plug Firing Voltage Firing line is affected by anything that adds resistance to the secondary circuit – Plugs, plug wires, engine temp, fuel mixture, and compression pressures Normal height between 7 – 13 kV with no more than 3 kV variation Snap throttle test should increase 3 – 4 kV

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Firing Line Examples

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Duration The amount of time the plug is firing Most engines have spark duration of about 1.5 ms Short duration cannot provide complete combustion A long spark line and short firing line may indicate a fouled plug, low compression, or narrow plug gap

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Duration

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Coil Condition The coil section shows voltage reserve Look at height of oscillations Should uniformly decrease to zero value Abnormal oscillations may indicate a short in the coil

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Primary Circuit Checks Firing section should show sharp oscillations Coil section should smoothly dissipate to zero Transistor on/off should be sharp

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Stress Testing Components Cold Testing – Cool components and watch patterns for malfunctions Heat Testing – Carefully heat with heat gun or hair dryer Moisture Testing – Lightly wet coil and plug wires

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Output Testing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Testing with a Scan Tool Many vehicles have onboard power balance testing May be automated test or allow individual cylinders to be disabled

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Diagnosing with a DSO or GMM Many have 2 – 4 channels for signal comparison May show DC volts, low amps, ignition secondary voltages, vacuum, and pressure Screens can be frozen, saved, and printed Can be connected and vehicle road tested

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using a DSO

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Which is most likely to cause a spark plug firing line to be significantly higher than the other cylinders of the same engine? A. Narrow spark plug gap B. Open plug wire C. Leaky fuel injector D. Incorrect ignition timing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Ignition Timing Controlled by the primary circuit Incorrect timing: – Incomplete combustion and excessive oxygen in the exhaust – Affect vacuum readings – Advanced timing can cause pinging or knock

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Follow the manufacturer’s procedures Make sure the spark plug gap and idle speed are correct before checking timing The engine must be at operating temperature Checking Ignition Timing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Supplies power to the ignition system Usually power is supplied to the ignition module and coil Ignition Switch

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Coil Resistance

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Crank/Cam Sensors Sensor air gap will affect system operation Measure with a non-magnetic feeler gauge Can be checked with DMM or scope

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Can be checked with DMM or scope Produces an AC voltage Pick-Up Coils

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Pickup Coil Waveform

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Hall-Effect Sensors May be tested by connecting 12 volts across positive and negative connection and a DMM across negative and signal wires Insert a steel feeler gauge between sensor and magnet and watch DMM voltage A logic probe can be used to check output

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Knock Sensors Watch ignition timing on scan tool and tap engine block with a hammer If knock is detected, timing will retard Check sensor electrical connectors and wiring

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Control Module Can be tested with a module tester Simulates operating conditions Usually very reliable May have to test indirectly – check module power and ground circuits, verify sensor input signals are present at module

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Distributor Service May need to be removed before service Inspect all wiring and connections Test advance mechanisms Check gear for wear or chipped teeth Inspect reluctor for damage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Lubricate O-ring Position rotor to align with marking Lower and fully seat distributor Install hold-down, cap, and wires Installing and Timing the Distributor

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Distributor Cap and Rotor Service Arcing between cap and rotor terminals deteriorates terminals Replace both cap and rotor together Make sure both are fully seated Arrange plug wires properly on cap

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. DIS Systems A problem on one cylinder may affect its companion cylinder Separate primary circuit for each coil Test each coil’s primary and secondary wiring Proper plug torque can affect ground circuit

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Coil-On-Plug Systems Individual coil problems affect only one cylinder Coils can be tested with ohmmeter Cylinder misfire codes can result from injector, plug, coil, or engine mechanical problems

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Plugs Carefully twist plug boot and pull wire from spark plug

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Plugs (Cont.) Use compressed air to blow any debris from the base of the plugs

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Plugs (Cont.) Remove the plug and inspect threads and cylinder head for damage Never remove plugs from a hot engine

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Inspecting Spark Plugs Note deposits and degree of electrode wear Normal color is grey or tan Gap should increase no more than 0.001” for every 10,000 miles of service Reading spark plugs can reveal a variety of engine conditions

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Cold fouling Wet fouling Splash fouling Gap bridging Glazing Overheating Turbulence burning Pre-ignition damage Common Types of Plug Problems

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Worn Spark Plug

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Cold- or Carbon-Fouled

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wet- or Oil-Fouling

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Splash-Fouling

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Gap Bridging

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Overheating

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Preignition Damage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Regapping Spark Plugs The gap of both new and used plugs should be checked Do not reduce gap by tapping plug, use needle-nose pliers or gapping tool Keep ground electrode in line with positive

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Spark Plug Installation Wipe dirt from plug seats Verify plugs are correct replacements Adjust the gap as needed Check whether anti-seize should be used Install and hand tighten Torque to specifications

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Secondary Ignition Wires Inspect for cracks and worn insulation Check boots for cracks and hard, brittle conditions Check resistance with an ohmmeter Replace as a set Properly route to avoid cross-firing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Plug Wire Routing and Looms

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Why is it important to follow the manufacturer’s service procedures when replacing spark plugs?