Replacement of Spark plugs and HT leads.

Whilst the spark plugs and high tension (HT) leads are designed for a reliable 5 year life, some including Roger Parker, advocate the more regular replacement of spark plugs for optimal performance, fuel efficiency and emissions. This is an easy job, so there is no reason why an eager DIYer shouldn't take on a spark plug replacement every 2 years/24000 miles. Here is how it is done.

Tools required.
  • 10 mm socket for removal of engine inspection cover.
  • Spark plug box spanner (pictured right, costs about 5 quid from Halfords, it is long enough to reach the spark plugs found deep in the cam cover of the engine and well worth the investment).
  • A large phillips screw driver.

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Time required:

Spark Plug removal:

Before starting work, make sure that the engine is cold enough to work on.

1. Remove the engine inspection cover, to expose the engine as seen in A.

2. Remove the spark plug cover from the engine cam cover as shown in B- it is held on by two philips-headed screws.

3. Remove the HT lead, one at a time for the individual spark plug you are about to replace. Whilst it is unlikely you could mix up the order of the HT leads with this ignition system design, this method reduces the likelihood of a cock-up even more! In C one can make out the spark plug deep in the recess of the head.

4. Use the spark plug spanner and remove the spark plug.

5. Make sure that the new spark plug is correctly gapped (0.9 mm or 32 thousandth of an inch), and using the spark plug spanner install new spark plug into the engine. Ensure that the plug is adequately torqued in and replace HT lead. The lead should attach with a palpable 'snap'.

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HT lead removal:

Replacement of HT leads follows the same procedures as the spark plug instructions as above. Here are shown the 8 mm Magnecor ignition leads as retailed by Brown and Gammons. They are numbered, and are a direct swap for the original leads.

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