Time for a spark plug replacement
With a little luck, a lawnmower will start motoring after one or two tugs of the pull cord when first taken out after the winter. This, however, does not necessarily always transpire, with variety of start-up and operational problems often occurring. These can range from simple quick-fixes such as having to push the primer bulb a few times to ensure that the petrol is sufficiently distributed in the engine, to more invasive maintenance tasks like replacing a blocked air filter.
Indeed, one issue that is of utmost importance to the health of a lawnmower is its spark plug because when one is faulty, the lawnmower can suffer in a variety of ways. Just as in on-road vehicles, NGK SPARK PLUG offers a wide range of standard and precious metal Aftermarket replacements for all small engine applications, including lawnmowers. If a lawnmower’s spark plug has gone or is going bad, the key symptoms to be on the lookout for include:
- Difficulty starting the engine: If the lawnmower has been primed and yet still requires many tugs of the pull cord before it starts, there is a good chance the spark plug needs replacing. With an underperforming spark plug, the spark generated by the plug may not be strong enough to fully ignite the air-fuel mixture, which can result in flooding of the engine.
- Substandard engine performance: Once a lawnmower with a faulty spark plug is running, it is common for it to suddenly cut-out during operation. This means that it must be restarted which can prove to be even more difficult each time because the heat of the engine can cause the gap between the spark plug’s ground and centre electrodes to increase, resulting in an even weaker ignition spark.
- Poor fuel economy: A misfiring spark plug will lead to the petrol in the lawnmower’s engine failing to burn completely. The knock-on effect of inefficient combustion will lead to an increase in fuel consumption. Needing to refill a lawnmower more regularly than normal is a common symptom of one that needs a new spark plug.
- Worn appearance: Upon physical inspection of a lawnmower’s spark plug, it may become apparent that it’s time to install a new one. Cracks on the plugs ceramic casing or a centre electrode with a rounded top instead of a flat top are key indicators. If the spark plug is sooty, a thorough cleaning may be enough to restore full functionality. Particular attention should be paid to the threat of carbon fouling, however, because although it can destroy the spark plug, it is a symptom of a problem from another part of the engine such as an incorrect air-fuel mixture. Replacing the plug in this scenario will only postpone the problem.
How to choose the right plug
For optimum lawn mowing performance, spark plug quality is especially important. If a precious metal Aftermarket upgrade is available for a particular lawnmower, NGK SPARK PLUG recommends using it because their advanced design and durability reduce misfiring, prevent sooting and ensure a longer service life than standard types. Most importantly, however, is the avoidance of low-cost replacements. Three main reasons against fitting cheap replacement plugs into a lawnmower or in fact any internal combustion engine, are:
- Faster wear: Cheaper plugs often cause misfiring or wear more quickly, shortening their service life. This can mean poor running, unreliable start-ups and higher emissions and fuel consumption.
- Wrong heat range: Sometimes the heat range of low-cost plugs is incorrect. This can lead to overheating of the spark plug, resulting in engine damage in extreme cases.
- Interference issues: Lower quality spark plugs may not meet the ‘immunity requirements’ of radio networks, potentially causing interference problems.
Installing a new spark plug
NGK SPARK PLUG recommends the following steps when fitting a replacement spark plug:
- Disconnect the spark plug wire from the spark plug at the front of the engine. This is a safety procedure that prevents the engine from accidently catching fire.
- Using a socket wrench or better still, a spark plug wrench, loosen the spark plug that is installed. A certain amount of force may be required to unfix the plug. Once this has occurred, unthread it using a wrench or your hands in the same manner you remove a screw.
- Using a wrench or your hands, screw in the new spark plug. To guarantee easy installation, ensure that threads of the plug are in line with the socket threads. Never force it in!
- Check the torque specifications on the packaging and, using a wrench, adjust the new spark plug to the correct torque. Ensure that the plug is fitted neither too tightly nor too loosely.
- Reattach the spark plug wire to the spark plug and start mowing!
All new spark and glow plugs can be found in the NGK SPARK PLUG EMEA catalogue for small engine applications which is available here.