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Distributor Replacement and Ignition Timing Adjustment

Dan Ferrell writes about DIY car maintenance and repair. He has certifications in Automation and Control Technology and Technical Writing.

Replacing a distributor requires a special, but simple procedure.

Replacing a distributor requires a special, but simple procedure.

The average car owner can do a distributor replacement at home using a few tools:

  • Distributor wrench (if necessary)
  • Combination wrenches
  • Socket wrenches
  • New distributor, cap, and rotor
  • Timing light
  • Some common tools
  • Vehicle repair manual

Often, you can replace the ignition distributor without a distributor wrench, depending on your particular vehicle model. But you still need a timing light. If you don't have this light, you can loan one from your local auto parts store.

You may need screwdrivers, wrenches, and other common tools as well, if you need to remove one or more components to gain access to the distributor, depending on your particular model. And, if you are not familiar with the ignition system on your vehicle, you may also need your vehicle repair manual for your particular model.

If you don't have this manual yet, you can buy a relatively inexpensive copy from Amazon. Haynes manuals come with step-by-step procedures for many replacement, troubleshooting, and maintenance projects. So you can recoup your investment in a short time while keeping the manual on hand for many more car projects.

Index

1. Removing the Distributor

2. Installing the New Distributor

3. Ignition Timing Adjustment

4. Video: Setting Ignition Timing

5. Preventing Engine Performance Issues

Resources

Mark in which direction the rotor is pointing to initially, and then again after you remove the distributor.

Mark in which direction the rotor is pointing to initially, and then again after you remove the distributor.

A faulty distributor can seriously disrupt engine performance.

1. Removing the Distributor

Park your vehicle in a safe place and set the emergency brakes before you start removing the distributor.

Then, remove any components that block access to your distributor. Depending on your model, these could be the air cleaner assembly, electrical connectors, wires, or hoses.

Label wires, connectors or hoses, if necessary, so that you can reinstall them correctly.

Also, make sure to correctly establish the position of the distributor and rotor on the engine, as described in the next steps, before removing the distributor.

  1. Place aligning marks on the distributor cap and distributor body using a marker or liquid correction fluid. These marks will help you realign the cap to the distributor when reinstalling the cap.
  2. Unplug the electrical connector and, if your model has it, the vacuum advance hose from the distributor. Plug the hose with a small screw, and don't remove the plug until you have adjusted ignition timing. We’ll tell you how to set the ignition timing after installing the new distributor.
  3. Detach the distributor cap. On some models, you can detach the cap without disconnecting the spark plug wires. If you need to remove the wires at this point, label each wire position on the cap so that you attach the wires in their corresponding place on the cap.
  4. Unscrew the distributor cap or pop the metal clips holding the cap in place, using a screwdriver. Wiggle the cap off the distributor body and place it out of the way or remove it from the engine.
  5. Place a mark on the distributor so that you know which way the rotor is pointing. You'll use this mark when reinstalling the distributor. If possible, don’t remove the rotor from the distributor until you have removed the distributor off the engine.
  6. Make a note of the position of the vacuum advance, if your distributor has one.
  7. Place aligning marks on the distributor base and engine, so that you install the new distributor in the same position. Better yet, trace the base of the distributor on the engine, if possible, using a marker or liquid correction fluid. This outline will help you position the new distributor on the engine in the same position as the old one.
  8. Unscrew the distributor hold down bolt(s) and clamp. Depending on your particular model, you may use a ratchet, ratchet extension and socket wrench or crow foot socket. Or you may need to use a distributor timing wrench.
  9. Now, you are ready to remove the distributor from the engine. However, here's something you need to know as you remove the distributor.

    • If your distributor shaft has a helical drive gear, as you pull the distributor out, the shaft will rotate a few degrees clockwise or counterclockwise. You'll notice this by watching the rotor as you pull the distributor out.
    • Notice the direction and the amount of any rotation on the rotor. You'll need to install the new distributor following the same direction and amount of rotation of the shaft, but in reverse order.
    • For this purpose, make a second mark on the distributor indicating the final position the rotor points to, after you have removed the distributor. Just make sure you know which are the initial and final rotor marks.
  10. After removing the distributor from the engine, unscrew the rotor or pull the rotor off the distributor shaft, depending on your particular model.
  11. If you are installing a new distributor, transfer all the aligning marks you just made on the old distributor to the new one.
  12. If you are not installing the new distributor right away, block the distributor opening on the engine with a shop towel to keep dust or any other objects from falling into the engine.
Label each wire position on the distributor cap, if you plan to replace the cap.

Label each wire position on the distributor cap, if you plan to replace the cap.

2. Installing the New Distributor

Make sure your new distributor is the correct one for your application. Then follow the next steps.

  1. Install the new rotor by aligning the rotor inside tab with the groove or slot on the distributor shaft. If your rotor screws into place, you may need to align the round or square dowels with the holes in the distributor.
  2. Apply a light coat of engine oil to the O-ring on the distributor shaft.
  3. Align the mark on the distributor with the mark you made on the engine earlier. Also, if your distributor shaft has a helical drive gear, rotate the rotor so that it points to the second rotor mark made on the distributor as well.
  4. Install the distributor, allowing the rotor to rotate slightly (clockwise or counterclockwise, depending on your particular model) while it meshes with the drive gear, if the shaft has a helical gear.
    • You may need to rock the distributor a little to have the shaft gear properly mesh with the drive gear.
    • Some distributors come with drive lugs at the base that should align with the drive grooves in the camshaft.
  5. Once the distributor is in place, make sure it is fully seated against the engine block.
    • You may need to play a bit with the rotor position to allow the lugs and grooves to fit together If the rotor is off by one tooth of the drive gear, twist the distributor body to align the rotor; If that’s not possible, you probably didn’t align the rotor correctly before dropping the distributor into the engine, and you need to remove and start the procedure again.
  6. Double check that the aligning marks on the engine, distributor, and primary rotor mark, are all aligned. This will indicate you have installed the distributor correctly.
  7. Install the distributor hold down bolt finger tight and slightly loose. You may need to rotate the distributor by hand when setting the ignition time later on.
  8. Install the distributor cap. Align the notch or tab on the cap with the notch or tab on top of the distributor body. Wiggle the cap from side to side to make sure the cap is sitting correctly on the distributor. The cap shouldn't wobble. Then secure the cap to the distributor with the screws or spring clips. Properly installing the cap will prevent damage to the rotor and new distributor.
    • If you are installing a new cap, transfer the spark plug wires to the new cap, making sure the wires follow the same installation order on the old cap.
    • On some models, the ignition coil attaches to the underside of the distributor cap. If necessary, transfer the coil to the new cap. Also, some models attach the ignition module to the distributor body. Transfer any components to the new distributor as necessary.
  9. Plug any electrical connectors to the distributor. If your distributor has vacuum advance, leave the hose disconnected until you adjust ignition timing.
Use a timing light to adjust base timing.

Use a timing light to adjust base timing.

...spark plug gap and idle speed must be correct to properly adjust base ignition timing.

3. Ignition Timing Adjustment

The following procedure is a general guideline on setting base timing. This is important for the engine to operate correctly. Look up the timing specifications for your particular model. You may find this information printed on an emissions label under the hood, or your vehicle repair manual.

Your particular vehicle model may have its own specific procedure to adjust timing. But in general, the following steps still apply.

The emissions label may also give you the procedure to disable computer timing control, and the conditions to check or adjust ignition timing. However, make sure to check the vehicle repair manual for the proper procedure for your particular model.

For this procedure, you'll need a timing light and, if necessary, a distributor timing wrench.

  1. Make sure you know where the timing marks on your vehicle are located. In most cars, you'll find the marks on the crankshaft pulley (at the front of the engine and towards the bottom) or flywheel.
  2. Here, you'll also find a stationary notch, pointer or line that will indicate the current base timing as the engine operates. You'll see the timing using your timing light in the next steps. Basically, this indicates the position of piston number one relative to top dead center (TDC). Your emissions label or repair manual will indicate how many degrees before TDC (BTDC) you should set base timing.
  3. Keep in mind that spark plug gap and idle speed must be correct to properly adjust base ignition timing. If you need to check spark plug gap and idle speed, refer to your vehicle repair manual.
  4. Start the engine, engage the parking brake, and let the engine idle for about 15 minutes to bring it up to operating temperature.
  5. Shut off the engine and disable computer controlled advance. Disabling computer control advance varies by model. On some vehicles, for example, you need to disconnect a wire connector on the computer wiring harness, or jumping across the pins on the service connector, or removing the plug on the harness connector on the distributor. If necessary, check your vehicle emissions label or consult your vehicle repair manual.
  6. Connect the timing light. The timing light has three leads. Two of the leads connect to the battery and the third lead may connect directly to the metal connector of number one spark plug wire or clipped around the same wire without unplugging it from the spark plug. Consult the tool's operating manual, if necessary. During this procedure, keep the timing light leads away from engine spinning components like the fan and belts.
  7. If your distributor has a vacuum advance, make sure the hose is disconnected and plugged.
  8. Start and let the engine idle.
  9. Direct the timing light on the timing marks. As the light pulses, you'll see the timing marks stationary. The stationary line or notch will point to the current degree mark.

    • If timing specifications call for 10 degrees base timing BTDC, and the reference line is pointing to the 3rd degree mark, adjust timing.
    • Loosen the distributor hold-down bolt.
    • Rotate the distributor slowly clockwise or counterclockwise to make the reference line point to the 10 degree mark.
    • Tighten the distributor hold-down button.
    • Double check that the timing is correct.
  10. After adjusting base timing, shut off the engine:

    • Disconnect the timing light.
    • Connect the vacuum advance hose, if necessary.
    • Enable computer control advance

You can watch this procedure in the next video.

4. Video: Setting Ignition Timing

5. Preventing Engine Performance Issues

A faulty distributor can seriously disrupt engine performance. Fortunately, replacing a bad distributor is not that difficult, as long as you follow the proper procedure.

Also, when installing a new distributor, it’s recommended to replace the spark plugs and spark plug wires, especially if they are two years old or older.

A faulty ignition distributor can lead to:

  • Misfires
  • Erratic engine performance
  • Check engine light on
  • Engine failing to start

Some manufacturers recommend replacing these ignition components when installing a new distributor to ensure that high voltage reaches the cylinders without a problem, while replacing the distributor every five years or so.

Look up the recommendations for your particular model in your repair manual. Then, check the Resources section at the bottom, if you need more help replacing the spark plugs and wires.

This guide helps you install a new distributor, including adjusting ignition timing, as necessary. So you'll be able to get your car back on the road in about an hour or so.

Resources

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2019 Dan Ferrell