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Steve Q

Spark plugs guide and fitting

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Spark Plugs are a small, yet vital part for the running of your engine and they can also tell you what condition the engine is in. In addition, spark plugs are both cheap and easy to replace as well as being a regular serving item. The most seen types of spark plug conditions are seen below as well as what they could mean you’re your vehicle.




Fitting Spark Plugs


Step 1


Let the engine cool and make sure the ignition is OFF as you don’t want the vehicles electrical system to potentially run through you!

Then you can open the bonnet.



Step 2


Remove the engine cover from your vehicle. This step may not be applicable to certain vehicles, particularly classic vehicles.



Step 3


Locate the spark plugs. This will depend on the type of engine fitted to your vehicle. Four cylinder engines have four spark plugs on the top or side of the engine in a line. V6, V8, V10 and V12 engines have six, eight, 10 and 12 spark plugs respectively which will be evenly spaced on each side.


image.png.76991340ae152256e098ff81c6c62e81.pngspark plug layout on a four cylinder engine

Step 4


Remove the end of the HT lead attached to the spark plug which should just unclip from the spark plug. It’s worth doing one spark plug at a time so as not to get confused when you’re refitting the leads as incorrect fitment will affect the running of the engine. It’s also worth checking the condition of the HT leads because if they’re damaged then they too will need replacing.


Step 5


Remove the spark plug using the correct sized socket or spark plug removal tool. Once the spark plug is removed its worth checking its condition by using the above guide. Then use a feeler gauge to check the gap between the spark plug as you’ll need the same gap between the new plugs so in order to get a good spark. This will usually be between .028 - .060 inch. If you need a spark plug removal tool then you can buy it here




Step 6


Screw the new spark plug in by using your hand and then use the correct sized socket or spark plug removal tool to tighten the spark plug. Don’t over tighten the spark plug as it can cause damage to either plug or the head of the engine. Also I recommend to first screw the spark plug by hand as cross threading the spark plug could damage the head of the engine.



Step 7


Reattach the end of the HT lead and then repeat step 4 – 6 with each spark plug.



Step 8


Start the engine to make sure then engine is running properly. It the engine seems rough then I would advise to switch off the engine immediately and check that you have fitted the HT leads to the correct spark plugs.

If you need to buy spark plugs then you can get them Here

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