Chapter 47
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CHAPTER 47. Ignition Systems Overview. Performing a Spark Test. 47-1. Remove the high-tension lead or coil from the end of the spark plug. Performing a Spark Test. 47-1. Connect a spark tester to the boot of the coil or high-tension lead, and attach the clamp to a good ground.

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CHAPTER 47

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Chapter 47

CHAPTER 47

Ignition Systems Overview


Performing a spark test

Performing a Spark Test

47-1

  • Remove the high-tension lead or coil from the end of the spark plug.


Performing a spark test1

Performing a Spark Test

47-1

  • Connect a spark tester to the boot of the coil or high-tension lead, and attach the clamp to a good ground.


Performing a spark test2

Performing a Spark Test

47-1

  • Crank the engine and watch for a spark across the tester electrodes. A properly functioning ignition system will produce a blue spark. If there is no spark present, test the spark plug wire or coil, distributor cap, and rotor on that plug. If there is still no spark present, continue on to the next Skill Drill.


Inspecting the primary and secondary circuits

Inspecting the Primary and Secondary Circuits

47-2

  • Remove the secondary wire from the center terminal of the distributor cap, install a spark tester, and crank the engine to see if there is any spark coming out of the ignition coil.


Inspecting the primary and secondary circuits1

Inspecting the Primary and Secondary Circuits

47-2

  • Use a test light or connect the red lead of a multimeter to the positive terminal at the coil and the black lead to a good ground with the key switched on. A typical reading is 10 to 12 volts. If using a test light, the light should illuminate brightly.


Inspecting the primary and secondary circuits2

Inspecting the Primary and Secondary Circuits

47-2

  • Place the red meter lead (or the test light probe) on the negative side of the coil and the black lead on a good ground. Crank the engine. The test light or meter should rapidly switch on and off, indicating the coil is being triggered.


Testing the ignition coil

Testing the Ignition Coil

47-3

  • Inspect and test ignition primary and secondary windings of the ignition coil(s). All the coil terminals should be clean, secure, and free of corrosion.


Testing the ignition coil1

Testing the Ignition Coil

47-3

  • To test the resistance of the primary windings, place the ohmmeter leads on each of the two primary winding terminals. If the reading is not within specifications, the coil is faulty and must be replaced.


Testing the ignition coil2

Testing the Ignition Coil

47-3

  • To test the secondary windings, place one ohmmeter lead on the secondary tower terminal and the other to one of the primary terminals, or the coil secondary ground, if equipped. If the reading is not within specifications, the coil is faulty and must be replaced.


Testing the ignition coil3

Testing the Ignition Coil

47-3

  • If the coil readings are OK, perform a spark test as in Skill Drill 47-1 to verify that the coil can produce a spark which will jump at least 1/2" (13 mm).


Testing a pickup coil

Testing a Pickup Coil

47-4

  • Disconnect the electrical connector from the pickup coil.


Testing a pickup coil1

Testing a Pickup Coil

47-4

  • Measure the resistance between the two terminals of the pickup coil by placing the leads of an ohmmeter to each terminal of the pickup coil. If the reading is not within specifications, the pickup coil is faulty and should be replaced. If the reading is within specifications, wiggle the pickup coil wires while watching the ohmmeter reading. It should not change.


Testing a pickup coil2

Testing a Pickup Coil

47-4

  • Connect a lab scope to the pickup coil windings. Crank the engine over and observe the AC pattern.


Testing a spark plug wire

Testing a Spark Plug Wire

47-5

  • Disconnect the spark plug wire at both ends by grasping the boots on the ends and twisting while pulling the wire off. Inspect each wire for cracks, brittleness, or burnt spots.


Testing a spark plug wire1

Testing a Spark Plug Wire

47-5

  • Place one lead of the ohmmeter on each end of the spark plug wire. Flex the wire while reading the ohmmeter.


Testing a spark plug wire2

Testing a Spark Plug Wire

47-5

  • Replace the spark plug wires, start the engine, and lightly mist water on the spark plug wires or run a grounded test lead along each wire. If the readings are not within specifications or if the wires arc, replace the spark plug wires, making sure to route them in their factory positions to prevent damage.


Inspecting a distributor cap and rotor

Inspecting a Distributor Cap and Rotor

47-6

  • Remove the distributor cap from the top of the distributor by unscrewing it or removing the clips.


Inspecting a distributor cap and rotor1

Inspecting a Distributor Cap and Rotor

47-6

  • Check for cracks, carbon tracks, and burned terminals, and also check the center terminal for wear.


Inspecting a distributor cap and rotor2

Inspecting a Distributor Cap and Rotor

47-6

  • Check the rotor for burned contacts and cracks in the plastic housing. If the rotor is held in place by a retaining screw, make sure it is tight.


Testing the crankshaft and camshaft position sensors

Testing the Crankshaft and Camshaft Position Sensors

47-7

  • Remove the connector from the sensor by removing any lock clips that may be present, and pull the connector off.


Testing the crankshaft and camshaft position sensors1

Testing the Crankshaft and Camshaft Position Sensors

47-7

  • If it is an inductive-type sensor, use an ohmmeter to read the resistance, and compare the readings to the specifications. Replace the sensor if its resistance is too high or too low, indicating that it is defective.


Testing the crankshaft and camshaft position sensors2

Testing the Crankshaft and Camshaft Position Sensors

47-7

  • If the sensor is a Hall-effect or optical sensor, or the previous reading is normal, use a lab scope to observe the sensor signal and compare to a known good pattern. If faulty, replace the sensor.


Testing an ignition module

Testing an Ignition Module

47-8

  • Test all the input wires leading to the ignition module for proper voltage and ground signals.


Testing an ignition module1

Testing an Ignition Module

47-8

  • Check for proper output signals from the ignition module with the key set to run and while cranking according to the manufacturer's specifications. If the specified inputs are present but the ignition module will not produce the proper output signals, the ignition module should be replaced.


Testing an ignition module2

Testing an Ignition Module

47-8

  • Check the voltage drop between the ignition module and ground on the engine with a multimeter set to read volts. If the voltage drop is more than 0.1 volt, check for corrosion or rust between the ignition module and the surface it is mounted to. Clean the corrosion or rust and reinstall the ignition module.


Finding vehicle specifications

Finding Vehicle Specifications

47-9

  • Obtain the website address for the service information system used by your repair shop. There may be a user name and password for the business as a whole or each technician may have individual login information.

  • If not using an online service, obtain the service manual for the vehicle you are servicing.

  • Using the year, make, and model of the vehicle, locate the section that covers the ignition system. This section is usually located within the "Engine Performance" or "Engine Electrical" section; it may also be within the "Engine Controls" section.


Finding vehicle specifications1

Finding Vehicle Specifications

47-9

  • Locate and record the specifications for the pickup sensors, spark plug wires, ignition coil (primary and secondary windings), or any other related component. The specifications will be in ohms or volts, or sometimes in frequency (Hz).

  • Print out or write down the specifications for use at the vehicle while you are testing.


Replacing the spark plugs

Replacing the Spark Plugs

47-10

  • Check the electrode gap of each spark plug by finding the correct-sized gauge on the gapping tool and attempt to place it between the center and the side electrode.


Replacing the spark plugs1

Replacing the Spark Plugs

47-10

  • To gain access to a spark plug, first remove the spark plug wire by gripping its boot by hand or with a high-tension wire puller and gently pulling it off of the spark plug.


Replacing the spark plugs2

Replacing the Spark Plugs

47-10

  • Clean out the spark plug pocket with compressed air.


Replacing the spark plugs3

Replacing the Spark Plugs

47-10

  • Remove the spark plug, using the correct-sized spark plug socket.


Replacing the spark plugs4

Replacing the Spark Plugs

47-10

  • If the new plugs are equipped with a gasket, ensure they are installed properly. Install the spark plugs by hand to avoid cross-threading. Use a torque wrench to properly tighten the spark plug.


Replacing the spark plugs5

Replacing the Spark Plugs

47-10

  • Once the spark plug is installed, reinstall the spark plug wire by pushing it on to the terminal of the spark plug until it snaps into place.


Replacing the spark plug wires

Replacing the Spark Plug Wires

47-11

  • Remove one end of the wire (or boot) from the distributor cap, coil pack, or COP coil. Remove the other end from the spark plug with a high-tension wire puller by twisting the boot on the spark plug while gently pulling it off.


Replacing the spark plug wires1

Replacing the Spark Plug Wires

47-11

  • If dielectric grease is specified for the spark plug boots, use a cotton swab to spread a small amount around the inside of the boot.


Replacing the spark plug wires2

Replacing the Spark Plug Wires

47-11

  • Install the new spark plug wire by pushing one end onto the spark plug and the other onto the distributor cap, coil pack, or COP coil. The spark plug wires should be routed in their factory positions to prevent damage.


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