Fix It

Open the hood of your Liberty and locate the negative battery cable on the top of the battery. The battery sits on the drivers side of the engine compartment, right behind the drivers-side headlight assembly. Loosen the clamp bolt on the cable end with a wrench and remove the cable from the battery, isolating it from the terminals while you are working.

Locate the glow plug in question on the side of the cylinder head. The cylinder head is at the top of the engine assembly, running front to back along the engine block. Grasp the wire at the top of the glow plug at the boot and pull it straight off the plug. Lay the wire aside.

Place a socket over the glow plug, attach a ratchet, and turn the plug counterclockwise. Pull the plug out of the cylinder and discard it.

Caully insert the new glow plug in the cylinder head. Tighten the glow plug to 110 inch-pounds with a torque wrench. Snap the wiring harness connector onto the top of the glow plug. Repeat the process for the remaining glow plugs until you have replaced all that are defective.

Install the negative battery cable on the negative battery terminal. Tighten the clamp bolt with a wrench, making sure it is secure. Do not over-tighten it or you may damage the cable end or terminal. Close the hood of your Jeep.

Pop the hood, and find the ignition coils under the intake manifolds, located near the top of the engine. Remove the coils with the socket wrench set. Note where each coil came from, as you will need to put them back in place later. Under the coils, you will find the spark plugs.

Remove the spark plugs with a wrench. If they are slightly difficult to remove, spray them with WD-40 to loosen them.

Look up the gap size in the Owners Manual. Set the gap, using the spark plug gapper. Install the new spark plugs into the engine block with the spark plug wrench. Dont turn them too tightly.

Put the ignition coils back in place, and secure them. Lower the hood of the vehicle.

Remove the spark plugs from your engine. This procedure will vary greatly by engine and airframe, but most are designed with regular plug maintenance in mind. Removing plugs from an aircraft engine is very similar to removing them from a car engine; the primary difference is that many aircraft use thread-on plug wires instead of automotive-style plug-ins. To remove threaded plug wires, simply unscrew them from the plug ends.

Drop the spark plugs -- electrode-end down -- into your mason jars. Lower them carefully so as not to damage the slugs. You may need two or more jars to hold the plugs. Pour your naptha solvent onto the jars to a depth of about one inch, or enough to cover the plug threads. Try to avoid pouring the solvent over the tops of the plugs. Allow them to sit in the solvent for 30 minutes.

Remove the plugs from the solvent. You can allow them to air dry, but you can dry them in seconds using the air supply from your sandblasting setup. At this point, the carbon on the plugs should be soft enough to remove with the baking soda blasting media.

Fill your sandblaster hopper with baking soda and trigger the sandblaster to purge any residual sand from the system. Turn the sandblasting pressure up to between 150 and 200 psi.

Hold your plug tip about three to five inches from the electrode and spray it down with baking soda. Rotate the plug to clean all around the electrode tip and the ground strap. You can remove stubborn carbon deposits by lightly scraping them with the end of your gun or a copper wire brush. Continue blasting the plug until its free of all discoloration and carbon. Repeat with your remaining plugs.

Fill your soup pot with water and place it on an electric stove to boil. Drop the plugs one at a time into the water to dissolve the baking soda. This is where the whole process comes together. Mechanics have been sandblasting spark plugs for years, but the sand tends to get trapped inside the plug and lead to later fouling. Baking soda dissolves in water, but it isnt aggressive enough to remove really hard carbon deposits without prior softening with a solvent like naptha.

Dry the plugs with compressed air and reinstall them into the engine in the reverse order of removal.