Distributor cap replacement instructions vary, so always follow the manufacturer's instructions.
General replacement procedures are as follows:
- For spring-loaded caps, unsnap the clips and remove the cap. When installing the new cap, make sure the clips are snapped back into place.
- For spring-loaded j-hook caps, push down and turn. It will unlock. Lift up to remove it. Position the new cap in place, then push down and turn to lock.
- For caps with screws, use a screwdriver to loosen the two screws. Install the new cap and use the screwdriver to tighten the screws. Don't overtighten.
It is a good idea when replacing the distributor cap to remove the cap with the ignition wires attached. After you have installed the new cap, transfer the wires one by one onto the cap in their correct position. This way the firing order is accurate. If, for some reason after you replace the distributor cap, your vehicle does not function normally, check your firing sequence.
The distributor cap is mounted on top of the distributor assembly and an alignment notch in the cap fits over a matching lug on the housing. Therefore the cap can only be installed in one position, which assures the correct firing sequence. There is a tab or notch somewhere on the distributor body that must align somewhere on the distributor body that must align with a corresponding tab or notch in the cap. Once again, do not force something.
The rotor should be inspected and/or replaced when the distributor cap is replaced.
Each cylinder of an engine must produce power once in every 720 degrees of crankshaft rotation. Each cylinder must have a power stroke at its own appropriate time during the rotation. To make this possible, the pistons and rods are arranged in a precise fashion. This is called the engine's firing order. The firing order is arranged to reduce rocking and imbalance problems. Because the potential for this rocking is determined by the design and construction of the engine, the firing order varies from engine to engine. Vehicle manufacturers simplify cylinder identification by numbering each cylinder.
Examples of typical firing order.
Regardless of the particular firing order used, the #1 cylinder always starts the firing order, with the rest of the cylinders following in a fixed sequence. The ignition system must be able to monitor the rotation of the crankshaft and the relative position of each piston to determine which piston is on its compression stroke. It must also be able to deliver a high-voltage surge to each cylinder at the proper time during its compression stroke. How the ignition system does these things depends on the design of the system.