When you are dealing with a faulty distributor cap, the best bet is generally to replace it, the rotor and possibly even the wires. The distributor cap sends electricity to the spark plugs so the engine will run, but if the cap leaks or another issue is occurring, you may have difficulty getting the car to start.
Fixing a leaky distributor cap
If you suspect a leak, this could lead to water seeping into the distributor cap. In turn, this can short the circuit and cause the engine to stall or not start at all. You can check this by removing the distributor cap and looking for signs of moisture. A silicone sealant can be used to reduce the likelihood of leakage. While you do this, you will also want to check the condition of the rotor and the wires. If they appear damaged, or if you plan to use a sealant to prevent further leakage, you may want to replace the parts. The sealant will make it difficult to remove the cap in the future.
Replacing the wires and rotor
If you notice at least one wire is damaged, you should replace all of them. It is best to do this one by one or label the wires so you know which wire connects to which spark plug. You will need a spark plug socket to do this.
When it comes to replacing the rotor, you should be able to pull the old one out easily, but there may be a screw holding it in place. Just make sure you take note of the direction the part is facing. Install the new one in the exact position. If the placement is off, it could impact the ignition timing.
This work can be easy, as long as you have patience and take the appropriate precautions. However, if you're not confident in handling any auto repair project bigger than adding more fluids to the vehicle, you may be better off taking the car to a professional. Disconnecting the battery before you begin work is always wise, especially when dealing with wires and other electrical components. When you're done with the replacement, fire up the engine and take your car for a test drive. If you've done the work correctly, the car should run smoothly.