How to Find Out Which Spark Plug Wire Goes to Which Cylinderby Cayden Conor
If the spark plug wires on a vehicle are not marked before they are removed, you must know the firing order in order to know which spark plug wire goes to which cylinder. Because every vehicle is different, it is always a good idea -- even on four-cylinder engines -- to mark the spark plug wire location prior to removing it or to remove the wires one at a time if you are changing the plugs and wires.
Obtain the firing order for your vehicle. You can find the firing order in your vehicle's owner's manual or in a repair manual for your specific vehicle. If you have neither handy, an auto parts store employee might look it up for you. You also need to know if the rotor turns clockwise or counterclockwise.
Find the cylinder numbering. On most Chevy V8s, the driver's side is 1-3-5-7 and the passenger's side is 2-4-6-8. Cylinders 1 and 2 are always closest to the engine. On most four-cylinder engines -- no matter the make -- the firing order is 1-3-4-2 and the cylinders are numbered 1-2-3-4, with No. 1 being the closest to the front of the engine.
Number the terminals on the distributor. The No. 1 terminal is over the rotor when the rotor is facing the No. 1 cylinder when the engine is at top dead center. The No. 1 terminal on the distributor will be directly in line with the No. 1 cylinder if you were to draw a straight line from the terminal to the cylinder.
Route the No. 1 wire to the No. 1 terminal. The terminals are numbered either clockwise or counterclockwise, depending on which engine you are working on. For example, on a Chevy, the No. 1 terminal is at approximately 5 o'clock, and the No. 2 terminal is to its left, then the No. 3 terminal and so on. Route the No. 2 wire from the No. 2 cylinder to the No. 2 terminal on the cap. Repeat for all cylinders.