A d v a n c e d   A u t o   M a i n t e n a n c e




 

Ignition system…


The ignition system is powered by the battery and comprises the electronic control unit (ECU), the distributor, the spark plug wires and the spark plugs.  It’s responsible for delivering the sparks to the engine cylinders at the precise times required to combust the fuel/air mixture in the cylinders to generate the explosive force that drives the engine.  Optimal engine performance is compromised if this precise timing is not achieved due to wear in any of the ignition components or if the ignition timing deteriorates during the normal course of driving over time.  The following points are important for ensuring that the ignition system in your vehicle operates as intended to deliver the best possible performance of your vehicle’s engine:


Obtain the tune-up specifications for the ignition system directly from the vehicle itself…

The label on the underside of the front of the bonnet of your vehicle titled, “Vehicle Emission Control Information”, records details about the ignition system in your vehicle and its tune-up specifications which can relied upon, such as spark plug gap, ignition timing and idle speed, provided that the engine in the vehicle is the original, factory-fitted engine or one identical to it (such as a reconditioned engine of the same type).

The specifications for the vehicle’s engine on this label under the bonnet will generally be consistent with the specifications for the engine in the owner’s manual for the vehicle.  However, due to the fact that some vehicle models are available with different types of engines, the specifications for the engine in the owner’s manual for the vehicle can sometimes differ from those on the Vehicle Emission Control Information label.  If they do differ, it is the specifications on the Vehicle Emission Control Information label that should be relied upon, because those specifications relate directly to the engine mounted in the vehicle, provided that the engine in the vehicle is the original factory-fitted engine or one identical to it (such as a reconditioned engine of the same type).


Check the ignition timing every 12 months or 20,000 kilometres, whichever comes first...

Check the ignition timing of the engine every 12 months or 20,000 kilometres (12,000 miles), whichever comes first, and set it correctly according to specifications if it is found to be out of adjustment.  Incorrectly set ignition timing causes excessively high fuel consumption, poor engine performance and can also lead to serious engine problems such as piston damage which are expensive to rectify.

The correct ignition timing setting for a vehicle’s engine can be found on the Vehicle Emission Control Information label on the underside of the front of the bonnet.  Refer to a workshop manual for your particular vehicle for the correct procedure and equipment required for setting the ignition timing of the engine.


Inspect the spark plugs every six months or 10,000 kilometres, whichever comes first…

Remove the spark plugs and inspect them for the correct spark plug gap and for excessive wear every 6 months or 10,000 kilometres (6,000 miles), whichever comes first, where normal spark plugs are fitted or every 12 months or 20,000 kilometres (12,000 miles), whichever comes first, where high-quality spark plugs are fitted.

Replace the spark plugs if they’re no longer in a serviceable condition.  Ensuring that the spark plugs are in the best possible condition helps to ensure efficient combustion of the fuel/air mixture and leads to better fuel economy.  It also has a dramatically positive effect on the performance of the vehicle, resulting in greater responsiveness and crisper acceleration.


Spark plug gap…

The spark plug gap is the distance between the end-tip of the inner electrode of the spark plug and the inside face of the outer, curved electrode of the spark plug (which is itself attached to the threaded part of the spark plug).  It can be measured using feeler gauges which are available from your local automotive parts shop.  The correct spark plug gap for a vehicle’s engine can be found on the Vehicle Emission Control Information label on the underside of the front of the bonnet.

What tends to happen over the course of the operation of the vehicle is that the spark plug gap changes from the gap that is specified your vehicle’s engine.  The high voltage surging through the spark plug from the ignition coil and the explosive heat inside the combustion chamber (into which the spark plug is fitted) result in the wearing away of the centre and outer electrodes of the spark plug which causes the gap to change.

Spark plugs that no longer have the gap specified for your vehicle’s engine cause a deterioration in fuel economy and engine performance.  When the gap has changed, you can adjust the gap manually back to the gap specified for your vehicle’s engine using needle-nosed pliers to bend the outer electrode towards or away from the inner electrode and feeler gauges to measure the gap.  The feeler gauge that matches the specified gap should be a snug, sliding fit between the two electrodes when the gap is set correctly.  (It normally takes a bit of patience to get the gap ‘just right’ on each spark plug.)  However if the spark plugs exhibit other signs of significant wear, such as considerable combustion deposits on the electrodes, it may be better to simply fit new spark plugs.

It’s best to purchase spark plugs pre-gapped to the specifications of your vehicle’s engine, to save you having to gap them manually.  For example, the product code of the high-quality, NGK iridium spark plugs that I use is BPR5EIX-11.  The ‘11’ on the end of that code refers to the spark plug gap on these plugs which is 1.1 millimetres (about 1/25 inch), as required by my vehicle’s engine and stated on the Vehicle Emission Control Information label under the front of my vehicle’s bonnet.  If you can’t find spark plugs that are pre-gapped to match the spark plug gap specified for your vehicle’s engine, then you’ll need to adjust the gap on each spark plug manually as outlined above before installing them onto your vehicle.


Getting the right spark plugs for your particular engine…

When purchasing spark plugs, it’s very important to obtain plugs that are exactly suited to the particular engine in your vehicle.  The owner’s manual for your vehicle will often recommend one or more specific brands and models of spark plug for your vehicle’s engine.  Be sure to check that the spark plug gap of these recommended spark plugs is consistent with the spark plug gap specified on the Vehicle Emission Control Information label under the front of the vehicle’s bonnet.

If the owner’s manual for your vehicle doesn’t recommend at least one brand and model of spark plug, you can go to your local automotive parts shop where they can advise which brands and types of spark plugs are suited to your particular vehicle based on the extensive product catalogues that they possess.  They simply look up your particular vehicle in a certain brand’s product catalogue and read off the product code for the spark plugs that are suited to that vehicle.

There are also a lot of aids for selecting the right types of spark plug on the spark plug manufacturers’ websites online.  You simply enter the details of your particular vehicle, such as manufacturer, model, year and engine type, and the website returns the product codes of the spark plugs that are suited for your vehicle.  There might be a selection of normal-quality through to high-quality spark plugs.  NGK is a manufacturer that makes a range of spark plugs suited to both normal use and high performance use.


It’s better to use higher-quality spark plugs...

It’s better to use higher-quality spark plugs for your vehicle, made by a reputable company such as NGK.  Generally the higher-quality spark plugs with iridium or platinum centre-electrodes last much longer and maintain the correct spark plug gap for longer than normal-quality plugs.  On normal-quality plugs, the spark plug gap tends to change from specifications relatively quickly due to the wearing away of the electrodes.

Because the higher-quality spark plugs last longer and maintain the correct gap for longer than the normal-quality spark plugs, they only have to be removed from the vehicle and checked every 12 months or 20,000 kilometres (12,000 miles), whichever comes first, as opposed to every 6 months or 10,000 kilometres (6,000 miles), whichever comes first, for the normal-quality plugs.  This results in a significant saving of time.  I personally use NGK Iridium IX spark plugs and I’ve found that these high-quality plugs are available much less expensively on eBay than from your local automotive parts shop.


Replace the spark plug wires every 24 months or 40,000 kilometres, whichever comes first…

Replace the spark plug wires every 24 months or 40,000 kilometres (24,000 miles), whichever comes first, to keep the ignition system functioning at its peak and maximise the performance of the engine.  Over the course of twenty-four months, the spark plug wires can degrade internally due to the frenetic and continuous high-voltage activity associated with the ignition system and the hostile, high-temperature environment of the engine bay.  At the end of a full twenty-four months of operation, it’s easier to simply renew the spark plug wires altogether rather than go through the tedious process of checking each wire for defects.

Because the spark plug wires are relatively passive ignition parts that simply carry the high voltages from the distributor to the spark plugs and because they remain in what is basically a fixed position between the distributor and the spark plugs over the course of their operation, I don’t believe that it’s necessary to inspect the spark plug wires during their service life.  If you want to, you can wipe them over with kerosene from time to time to get rid of any build-up of grime on them.

NGK is a manufacturer that makes high-quality spark plug wires that minimise the electrical interference between the high-voltage ignition system and other sensitive electrical components on the vehicle such as the microcomputer which controls engine systems like electronic fuel injection.  I use and recommend NGK spark plug wires.


Replace the distributor cap and rotor every 24 months or 40,000 kilometres, whichever comes first…

Replace the distributor cap and the distributor rotor every 24 months or 40,000 kilometres (24,000 miles), whichever comes first, to keep the ignition system functioning at its peak and maximise fuel economy.  Over the course of twenty-four months, the electrical terminals inside the distributor cap and on the distributor rotor become burnt and oxidised from the frenetic and continuous high-voltage activity associated with the ignition system.

Since it’s generally not easy to restore these points of electrical contact to an ‘as-new’ condition, particularly inside the distributor cap, it’s best to renew the distributor cap and rotor altogether.  Together with the spark plugs and spark plug wires, the distributor cap and rotor have a decisive effect on the performance of the ignition system which affects the performance of the engine and fuel economy.



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Copyright 2016 Andrew Mackinnon.  All rights reserved.