If your older vehicle won't start, stalls, or backfires, you likely have a faulty distributor cap. A distributor cap passes the needed voltage from the ignition coil to the engine cylinder heads, but newer vehicles produced after the early 2000s employ a computerized ignition system. 

Replacing a distributer cap is often the first thing mechanics learned to replace before the computerized ignitions. Replace the distributor cap and rotor yourself by following these tips.

Prepare to Replace the Distributor Cap and Rotor

To replace the distributor cap, gather:

• work gloves
• marker
• masking tape
• flat-blade and magnetized screwdrivers
• wrenches
• socket set 
• spark plug wires 
• replacement distributor cap and rotor  

Park the vehicle in a lighted area, and let the motor cool. Raise the hood and locate the distributor cap, which is often black or gray with spark plug wires attached, or refer to your manual. Use pliers to disconnect both battery cables, and point them away from the terminals. 

Remove the Old Distributor Cap and Rotor

You may need to remove the engine cover and filter housing according to instructions in your manual. While you detach the cap, mark the location of the engine spark plug wires. 

Begin disconnecting them in the noon position, then wrap them in tape and label them working clockwise, so you get the correct firing order. If you prefer, you can remove the cap without removing wires, or find a firing order diagram for your vehicle.

Remove the wires from the cap using the same method. Inspect to see how the distributor cap attaches, which is commonly by clips, bolts, or screws. To remove clips, pop them using a flat-blade screwdriver, or press them in, then rotate them to the left. Remove bolts with the correct socket or wrench, or remove screws with a screwdriver.

You will also need to remove the rotor, the object in the distributor housing with a blunt end and pointed end. Lay a flat-blade screwdriver along the rotor edge to mark the position of the pointed end. 

Lift the rotor out, or use the magnetized screwdriver to unfasten the screw to avoid it falling into the distributor shaft. Don't reuse the old rotor screw.

Install the New Distributor Cap and Rotor

Set the new rotor in place, using the marked position indicated by the screwdriver for the pointed end. Secure the rotor with the screw provided in the replacement. 

Install the new cap, securing the clips or screws. Reconnect the two sets of spark plug wires following the marking order, reinstall the other parts, then reconnect the battery cables. Start the engine and test the repair.

For more information, talk to a company like Redford Auto Repair.