How to Remove, Install, and Adjust Ignition Timing

ignition distributor in open engine

Ignition distributors are used in gasoline engines to provide a properly timed, high voltage to the spark plugs. A gasoline engine cannot run on gas and air alone. The engine must have a way to ignite the gas and air that enter the engine’s combustion chamber. To do this, a spark plug is threaded into an area of the combustion chamber and high voltage is sent to the plug from an ignition coil. This creates a spark which ignites the air and fuel creating an explosion which heats the air and forces the piston down, creating power.

The distributor is used to distribute the high voltage from the coil to the appropriate spark plug, at the correct time. A distributor may need to be removed from an engine as part of a repair procedure or require replacement due to a mechanical problem such as a worn distributor gear or broken distributor shaft. In this guide, we will cover the steps required to remove, replace and retime the ignition distributor.

Part 1 of 4: Taking apart the battery cable

Materials Needed

Step 1: Disconnect the negative battery cable. Before you remove a distributor you should disconnect the negative battery cable so that no one can crank the engine while you complete the procedure.

green arrow pointing to a distributor inside an open engine

Step 2: Locate the distributor. You will need to locate the distributor. It is commonly located on the top of the engine block in either the front, or rear of V-6 and V-8 engines, or on the side of the block on 4 and 6 cylinder engines.

distributor showing wires coming out of it

The distributor has a plastic cap with spark plug wires coming out of the top of the cap. Each of these wires goes to a corresponding cylinder spark plug and must be in the correct position for the engine to run.

numbered distributor cap terminals for reference

Step 3: Mark spark plug wire position. You can use popular service information repair manuals for the vehicle or the cylinder numbers printed on the spark plug wires.

Identify the engine cylinders and mark each wire on the distributor by using masking tape or a permanent marker. Label each wire’s corresponding cylinder number so that they can be installed in the correct order.

marking the rotor pointing direction

  • Tip: If there is an arrow indicating rotation on the cap, make sure you note which direction the numbered wires should be installed on the cap.

Step 4: Remove the distributor cap. Distributor caps are typically held in place by clips or screws.

Either disconnect the clips or turn the screws to release the cap from the distributor.

  • Note: The following steps are very important for starting the engine later. Once the cap is removed, you will need to make a mark on the engine, fender shield, radiator or some other clean area directly in-line with the direction that the rotor points.

showing distributor rotor lining up with a mark on the distributor

Step 5: Mark the housing. Make another mark on the distributor housing so you know where the rotor was pointing on the distributor.

Step 6: Disconnect wiring and/or vacuum lines. Disconnect any primary electrical wiring or vacuum lines the distributor may have.

On a points and condenser type, you may need to disconnect the primary electrical wire coming out of the distributor at the ignition coil. On an electronic ignition you may follow the small wire harness that comes out from the distributor and locate the connector.

Step 7: Disconnect the connector. Remove the connector from any brackets holding it in, and pull the locking tab to disconnect it.

using arrows to call out clamp and hold down bolt

Step 8: Remove hold down bolt and clamp. The distributor is held in place by a bolt typically called the hold down bolt.

Remove the bolt and the clamp that is under the bolt. When you have removed the bolt and clamp, you can lift the distributor body out of the engine block.

  • Note: On older vehicles it may take some force to remove the distributor.

  • Tip: If it appears the distributor is corroded to the engine block, use penetrating oil and let the penetrant soak for 15 minutes to aid in removal. Do not attempt to hit the distributor with a hammer as most distributors are made of cast aluminum and will be damaged.

Part 2 of 4: Inspecting the distributor

Step 1: Inspect the distributor. Once the distributor is removed, look at the drive gear on the bottom of the distributor shaft.

It should not be loose or appear to have any significant wear or chips missing in the gear. The distributor shaft should spin freely without significant play. If you find either of these problems when you inspect the distributor it should be replaced or possibly repaired by a YourMechanic technician.

Part 3 of 4: Installing the distributor

motor aligning with the mark above it

Step 1: Distributor installation. To install the distributor, you will need to line up the rotor with the mark you made on the engine or other clean area.

Attempt to align the rotor with that mark as you lower the distributor into the engine block.

Due to the distributor and camshaft gears being helically cut (cut at an angle), you will need to position the rotor approximately 30 degrees one way or the other as the gears will cause the distributor shaft to turn slightly as you engage the gears together.

  • Tip: You may need to insert and remove the distributor several times to get the correct alignment. Once you have achieved the correct alignment of the rotor to the mark you made previously, make sure the distributor is fully seated into the engine block. If the distributor is not seated fully, pull the distributor up slightly and reseat the distributor until it is fully seated.

Step 2: Install hold down bolt and clamp. Install the hold down clamp and, using just finger pressure, slightly snug the hold down bolt in place.

Leave enough play so that the distributor can be turned left or right by hand with moderate pressure. Make sure to keep the rotor lined up with your alignment mark after checking.

Step 3: Reconnect wiring and install rotor. Reconnect your wiring connector or primary wiring to your ignition coil.

If you have not done so, install the plastic rotor back on the top of the distributor shaft and install the cap in place.

Step 4: Install distributor cap. Install the cap and begin inserting the spark plug wires by locating in the correct order from the markings you made before removal.

Step 5: Connect battery. Reconnect the negative battery terminal and make sure you have picked up any tools that may be still in the engine compartment.

You will next need to adjust your ignition timing.

  • Tip: If you removed a vacuum line from the distributor you must plug the vacuum line coming from the engine to eliminate a vacuum leak by using a small bolt or even a golf tee.

Part 4 of 4: Check ignition timing

Material Needed

inductive timing light in use

Step 1: Check the ignition timing. You will need an inductive timing light to complete the base timing check.

This tool uses an inductive clamp that is placed around the number one cylinder’s spark plug wire. There will also be two electrical connections (positive and negative) from the timing light that need to be connected to your vehicle’s battery for the light to work.

Step 2: Locate the electronic base timing procedure. If the vehicle uses an electronic distributor, you will need to locate the electronic base timing procedure for your vehicle.

engine compartment with arrows in the areas shown to demonstrate typical label placement

Sometimes the procedure can be found labeled in the engine compartment of your vehicle. The procedure will outline how to get the vehicle’s engine computer into a base timing mode which will allow you to adjust the ignition timing correctly.

Step 3: Attempt to start the engine. If the engine does not start, you can move the distributor slightly with your hand either clockwise or counter clockwise and attempt to start the engine.

You may feel the engine try to start or not want to start at all. Continue to move the distributor slightly in the direction that feels as if the engine will want to start.

When the engine starts and runs you may begin the timing procedure after the car has warmed up to normal operating temperature.

Step 4: Check the operation of timing light. Make sure you have connected it to the vehicle and are squeezing the trigger while the engine is running.

You will notice the light flashes rapidly. This is normal operation and, if it does not flash, you should double check all of the connections for the timing light.

Step 5: Consult service information. You will need to consult service information to know what the timing adjustment should be for your vehicle.

Many times it can be found on the radiator support of underside of the hood. An example of a common base timing adjustment is 10 degrees BTDC (before top dead center).

timing marks etched on transmission to illustrate number notches

Step 6: Find the timing marks on your vehicle. They are typically located just behind the crankshaft pulley on the front of the engine or on on the top of the transmission housing at the back of the engine.

There should be a line or a pointer attached or cast into the engine block or transmission.On the engine side of the crankshaft pulley or on the transmission torque converter/flywheel there will be numbers in a range of -15 to 5 with a zero in the middle. These numbers indicate timing in degrees of retard (negative numbers) or advance (positive numbers).

Step 7: Use the timing light. Point the timing light at the timing marks and pull the trigger, as the flashing light makes the numbers appear as if they are stationary.

Make sure that the engine is idle and warmed up and that you have plugged the vacuum line to the distributor (points system) or set the vehicle into base timing mode (electronic distributor).

Step 8: Adjust the timing. While holding the timing light on those marks, slowly move the distributor so that the line or pointer corresponds to the number you want your timing to be.

An example would be to have the pointer on the -10 if the specifications were 10 degrees BTDC (before top dead center). The “before” means the spark will happen before the piston gets to top dead center and that is indicated by the negative number on the vehicle timing marks.

If the specifications were 5 degrees ATDC (after top dead center) you would move the distributor by hand until the pointer or line indicated 5. This means the spark occurs 5 degrees after the piston has reached top dead center.

Step 9: Tighten the hold down bolt. When you have set the timing in the desired position, shut off the engine and tighten the hold down bolt so that the distributor will not move.

Step 10: Set the vehicle back to normal. Depending on application, either reinstall the vacuum line to the distributor or place the vehicle back into computer controlled timing.

Step 11: Double check and finish up. Double check the engine compartment for tools, close the hood and check to make sure it is latched properly.

You have just removed and replaced your distributor and also set your ignition timing!

Now that the distributor is operating as it should and is properly timed, now may be a good time to inspect the condition of your spark plugs to ensure your engine is running as efficiently as possible. To complete your tune-up, take a look at your air filter as well. A dirty air filter can have a severe effect on fuel mileage, engine performance and engine wear over time.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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