Air Cooled VW Spark Plug Service

Spark Plugs Replace or Clean and Re-gap?

Your spark plugs will not need to be changed at every tune up, however they should be inspected and replaced if necessary. Most of the time you can clean up your spark plugs, check the gaps and reset if needed and get more mileage from your plugs. Some mechanics will replace the spark plugs at each tune up, but that is really a waste of both money and resources. “Experts” recommend that you replace your spark plugs every 12,000 miles.

When you take out your spark plugs be sure to arrange them in a way so that you know exactly which cylinder they came from. The condition of each spark plug when it is first removed from the cylinder head will give you insight into the internal conditions of your engine. For example, if all your plugs are relatively clean except for one that is burned or covered with oil or build up you know you have a problem in that particular cylinder.

Your spark plugs should be dry and have little or no deposits or build up. If the center electrode has become worn and rounded around the edges you will not be able to get a sufficient spark for good performance – replace the plug, and of course, don’t just replace one, get a complete new set.

If your spark plugs are dirty you can clean them, but the engine conditions that caused them to get that way will still be there.

Normal Spark Plug

Normal Spark Plug

In the photo you will see what a normal spark plug should look like. There are minimal deposits that are light in color and the edges of the electrodes are straight and intact.

Normally the deposits on your spark plugs will be carbon.

If you see a light colored deposit on the plugs it isn’t anything to worry about as it is normal and usually cleans very easily.

If the carbon deposits are black, but can still easily be removed your air/fuel mixture is too rich and so a carburetor adjustment will be necessary.

If the deposits are black and hardened, burned, or sticky looking you have oil entering the fuel chamber most likely caused by worn rings. If your spark plugs looked like this what was the compression reading?

Setting The Gap On Your Spark Plugs

  • Set of 4 spark plugs, either brand new or used
  • Spark plug gapping tool or flat feeler gauge set
  • Tool Box

First look at the electrode end at eye level. The side electrode must be directly above the center electrode. If you don’t have a spark plug tool use small needle nose pliers to adjust the side electrode. Once the electrodes are lined up adjust the gap, then recheck the alignment until both are correct.

The metal gaskets on the spark plugs are important, don’t let them get lost.

The gap setting for nearly all air cooled Volkswagen engines is 0.028 inches.

Before inserting the spark plugs back into the cylinder head wipe a very light coating of oil on the threads. Remember, light, you don’t need oil running down into your cylinders. Thread the spark plugs in as far as you can by hand. A good way to do this is to place a spark plug socket with an extension over the plug and turn it by hand. Once you get the plug hand tightened as far as you can turn it about half a turn further with a ratchet, be careful not to over tighten as that will alter the electrode gap and cause serious damage to the head.

I once owned a bug which the previous owner had nearly stripped the threads in one of the spark plug holes. If I accelerated too quickly it would actually blow that spark plug right out of the hole!

Proceed to StepĀ 5 of tune up procedure How To Set Ignition Timing On An Air Cooled VW

Written by David Slone, Copyright 2008 AirCooledVWLove.com

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2 Comments

  1. Morris says:

    I am having truble getting the spark plugs out of a 1600 vw eng. 1973 super can anone help

  2. Bugwisr says:

    For Morris on his spark plug removal issue: coat the plug with rusteater, WD-40 or the like and let penetrate. This will work with minimal effort.

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