Basic ignition systems used to have a distributor and coil pack that would mechanically send the current to each spark plug. Today's ignition systems use individual coil packs that are computer controlled, making the engine work more efficiently and save on gas mileage. When it comes time to replace the spark plugs, you have to remove the coil packs first. In this case, the project vehicle is a 2005 Mercedes-Benz C230, but the process is similar for other vehicles as well.
Allow the engine to cool completely prior to working on it--at least five hours. Pop the hood. Lift off the engine cover using your hands and set it to the side. Unbolt the first coil pack from the top of the engine using the 3/8-inch ratchet and socket and pull it up with a twisting motion to expose the spark plug. You may have to disconnect an electrical harness at the coil as well.
Remove the stock spark plug using the 3/8-inch ratchet, extension and spark plug socket. Discard the old plug.
Gap the spark plug using the spark plug gapping tool set to .031-inch. Install the replacement spark plug using the 3/8-inch ratchet, extension and spark plug socket. Reinstall the coil pack onto the spark plug, pushing it onto the plug until it makes a popping noise. Then bolt it to the head using the ratchet.
Repeat Steps 1-3 for any remaining spark plugs in the system.
