Though increasingly less common since the start of the 21st century, mechanical distributors are a common feature in many older cars. Most distributors require relatively little maintenance outside of replacing the cap every so often, but when they do you need to know how to replace one.
First turn the engine to top dead center and disconnect all wires from the distributor. Disconnect the distributor by removing the holddown clamp and pulling it out. Install new distributor set to facing number 1 ignition wire and shaft lubricated.
Signs of a Bad Distributor
To be sure you’re distributor is bad, you’ll to get out some tools and check a few things. However, there are some signs you can look out for that will indicate you should check your distributor.
- Trouble starting: If your car has trouble starting, especially in cold weather, your distributor cap may be cracked. The heat produced when starting the engine in cold weather can crack the cold distributor cap.
- Shaking: A car that shakes while running could indicate the distributor is not spinning properly. If this happens, the timing and firing may be off.
- Squealing: Although squealing can have a number of causes, it may be caused by a dirty or broken distributor. You should clean the grease and grime under the distributor cap. Then, if the car still squeals, the distributor may need replaced.
What You Need to Replace Your Distributor
Gather Your Supplies
- A spark tester
- A ratchet
- A screwdriver
- A socket
Checking the Distributor
- Inspect the distributor cap. Check the distributor cap for signs of rust or corrosion. Also, check how to sporks are arcing. Then, look at the rotor for signs of burns or carbon.
- Inspect the contact points. Check the condenser. An open conditioner could mean you have a broken wire lead.
- Check the arc: The safest way to do this is to insert a spark tester into the end of one of the wires like you would a spark plug. Then clip it to a metal part of your engine. Have a friend crank your engine while you watch from a safe distance. If you see a spark that wire is working.
How to Replace a Distributor
Replacing a distributor isn’t that hard you will need basic hand tools and some motor oil. Follow these steps.
- Locate your distributor. They are located in many points of the engine, but you can find it by tracing the ignition wires from the spark plugs.
- Disconnect the negative battery terminal. This probably doesn’t need said but never cross both terminals.
- Set engine to top dead center. You can locate this by locating cylinder number one and removing spark plugs. Stick a pencil in and turn the engine until it reaches its highest point. Ensure your timing marks located on the crankshaft and engine block line up and then mark them with bright white paint, marker, or correction fluid.
- Remove all wiring from the distributor. Mark each wire starting with number 1 and the corresponding location on the distributor cap. If the distributor has any vacuum advance lines remove these and set aside as well.
- Remove the cap. If the engine has been running well and the distributor is only being replaced due to age mark where the distributor is facing on the side of the distributor and the engine so the new distributor can match it.
- Remove the holddown clamp. The location of this varies, but typically there will be a single bolt to remove.
- Slide the distributor out. This may be difficult but with a bit of musclework it should slip out.
- Prepare the new distributor. The distributor shaft should be lubricated and set to facing the position of the wire for cylinder number 1. This should be the same as the distributor that you just removed.
- Insert the new distributor. Avoid altering the position of the rotor. This may be difficult but make sure the position is right when it becomes fixed to the engine.
- Install the cap, wires, and any vacuum lines. Make sure the wires are all in the correct order. A firing order diagram will help if you do not remember the positions. Reattach the negative battery terminal as soon as all the wires are installed.
- Start the car if you are not changing the timing. Otherwise set the timing now. If the car is misfiring upon starting or won’t start at all most likely it is the timing or you have placed the wires in the wrong order.
Setting the Timing
Distributor timing is the most easily set part of your engines timing and the part you will probably be doing the most on an older car. Here is how.
- Set your timing marks. You should have already made your timing marks when you set the engine to top dead center earlier, but if you didn’t do it now.
- Attach a timing light. Attach the positive and negative clamps to your battery, and the timing clamp to the number 1 cylinder wire.
- Loosen the distributor hold down clamp. It is best to do this step before the engine is warmed otherwise, be careful not to get burned.
- Remove vacuum advance. Generally this will prevent the timing from being altered and making it difficult to achieve the proper setting.
- Start the engine. A partner to help keep start the engine if and when it stalls can be a big help.
- Rotate the distributor to set the timing. The proper setting depends on your car, but in a pinch between 0-10 degrees before top dead center will generally work.
- Retighten the hold down clamp. Also reattach the vacuum advance if present.
- Listen. If the engine seems to be running well your done.