Page 261 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

However, there are many ways to effectively manage Ignition Coils and prolong their lifetime, some as simple as
paying extra attention when connecting the Ignition Coil to the Spark Plug, as misalignment can cause severe
Spark Plug damage.
For the Electronic Ignition Control, the Diagnostic Trouble Code (DTC) engine warning light will probably be
turned on, indicating an ignition error – however, this might be caused by another system problem.
Common indicators of a failed ignition system

While newer cars fitted with a ‘distributor’ engine ignition coil do see fewer issues. No car is immune to electrical
problems. These generally emanate from the coil packs and the plugs or are signs that related sensors have seen
better days. Typical indicators of a failed system include:

Loss of engine power: Any problems with the ignition system mean a loss of engine power, due to voltage that’s
not delivered to plugs to ignite the air and fuel mixture. This can be from worn or fouled spark plugs, fraying in
spark plug wires, or damage to coils and coil packs requiring you to buy a new engine ignition coil.
Stalling and hard starts: The role of the ignition is to provide the right voltage at the right time so combustion
occurs. Malfunctioning coils or faulty plugs mean this doesn’t happen, and results in difficulty turning the engine
over, or repeated stalling. Related issues are unburnt fuel that clogs the exhaust and catalytic converter.
Changes in engine noise: clicking sounds and the engine not starting point to a failed starter motor (or depleted
battery). In addition, misfires or failed combustion in any cylinder lead to the engine coughing or sputtering and
are accompanied by pronounced vibrations due to bad ignition timing. Backfiring or the fuel combustion outside
the cylinders (most often in the exhaust), is a loud and unnerving sound that also points to faults in either the
plugs or the coil.
Rough idling: this is a related issue of missed ignition timing that doesn’t correspond to engine speeds and
fueling. You’ll notice vibrations as RPMs repeatedly rise and fall. And when sudden jolts when pressing the gas
pedal.
Poor fuel economy: if all parts are working as they should, then sparks happen at the right time and ignite
the designated amount of fuel for the engine load. With faulty ignition components, drivers may notice a
substantial increase in fuel use, this is down to low voltage in the coils, soiled or damaged plugs, and the ECU
overcompensating by spurting more fuel from the injectors.
During any of the problems above, drivers will also see the ‘check engine’ light in the dash. When running a
diagnostics test with the car connected to an OBDII scanner or computer, most cases point to damaged coil packs
or plugs.
Issues can also arise due to bad sensors, most notably the oxygen sensor, and the camshaft and crankshaft
position sensors. Though rare, newer vehicles can experience problems with the ignition module, or the electronics
controlling the ignition, and separate from the ECU.
Coil Pack Issues
Most manufacturers today don’t consider an engine ignition coil as a regular replacement part. There are vehicles
with 200 thousand plus miles on the odometer, and no signs of ignition failure, or any of the symptoms stated
above. Not all coils are created equal though, and not all drivers are that lucky.

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CITS : Automotive - Mechanic Diesel - Lesson 76 - 79