Series Land Rover (U.S.A./Canada)
Serving the Series 1, Series 2, Series 3 and other Land Rover communities worldwide.

Light coloured, dry electrodes shows all is well.

Dry, sooty, black even coating on electrodes suggests an over-rich fuel mixture or blocked air filter.

Wet, black and shiny electrodes suggests oil entering the cylinder.

Plugs are easily removed for inspection but it is often forgotten how devastating a small piece of grit can be if it enters the cylinder bores. So be very careful to always wipe arund the spark plug base before completely removing it from the cylinder head.

Common visually diagnostic problems are illustarted in the above photos but there are other conditions that may lead to spark plug under performance:

Fuel additives: there are a variety of commercially available additives that can be added to fuel to treat engine ailments, increase performance or improve engine componet functionality. Whilst these substances may perform the task they were designed for very well, they are prone to leaving behind deposits when they burn - thus affecting spark plug appearance and functionality. So if you are using additives for treating a sticking valve, for example, check on the spark plugs and be prepared to replace them sooner than normal.

Oil additives: a number of oil additives are available for reducing friction, re-coating worn surfaces etc and some oil does inevitably get into the cylinder bores evn if compression is good. Again these additives are not designed primarly for their clean burning characteristics so spark plug condition can be affected.

When inspecting a spark plug don't forget to inspect the electrodes for corrosion and the insultor for cracking. Cracking can be caused by a loose plug terminal causing a spark inside the protective rubber sheath. Look for tell-tale flashes around the plugs whist the engine is running on a dark nght.

When replacing spark plugs remember that a standard Series Land Rover engine requires a specific spark plug type. Generally a 2.6litre engine can use Champion N5 or equivalent; 2.25litre engines can use N8 if 7:1 compression and N12Y if 8:1. For earlier, smaller engines, try either N5 or N8.

Spark plug gap is important for electrode health. Set to 0.030in for 2.6litre engines and 0.025in for all other standard Series Land Rover engines.

If oil on the plugs is a problem but engine overhaul is not possible in the short term, then you could try using a spark plug with a higher temperature rating than the standard one as this will run hotter and burn off the oil.

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