How to Set the Timing With a Dwell Meterby Chris Stevenson
Many vehicles come with breakerless ignition points systems. Ignition points have contact points that open and close, according to the position on the distributor shaft cam lobe. The high and low spots on the cam lobe govern the length of time the points are open and closed, which sends a voltage signal to the spark plugs for firing. The open and closing duration times the spark to each cylinder. A vehicle owner can use a dwell meter to set his ignition point timing, according to manufacture's specifications, then synchronize his basic timing. The following instructions should only be attempted by experienced home mechanics.
Place the vehicle transmission in "Park" for an automatic and "Neutral" for a manual version. Apply the emergency brake and raise the hood. Do not work on a hot engine -- let it cool somewhat before making the adjustment. Look at your distributor cap and determine if it has an adjusting window on the side of the cap. If it does, you will set the points with an Allen wrench. If not, remove the distributor cap by turning the two cap hold-down springs outward with a slot screwdriver, or unscrew the cap with a Phillips screwdriver.
Hook up the red lead to a dwell meter on the negative (-) terminal on the ignition coil or coil pack. Refer to your owner's service manual if you are unsure of the coil or coil pack location and terminal position. Hook up the other meter lead to a good engine ground source. For the adjustable window distributor, set the meter for the degree or "Dwell" scale. Place an Allen wrench through the adjustment window on the distributor cap, connecting it to the adjustment screw.
Instruct an assistant to start the engine. Read the dwell in degrees on the dwell meter screen. Refer to your owner's manual for the correct dwell angle setting (i.e. 30 or 32 degrees). Turn the adjustment screw in (clockwise) to increase the dwell, or out (counterclockwise) to decrease the dwell. Once the needle reads the correct number, withdraw the Allen wrench and shut the engine off.
Wedge the distributor cap away from the distributor body, with the bottom facing up. This procedure works for the non-window distributor cap. Remove the rotor with a screwdriver, or by hand. Loosen the two screws that hold the points in place on the distributor plate. Loosen them only enough so the adjustment arm on the points move. Place a slot screwdriver in the adjustment slot on the points and have your assistant turn the engine over. Read the needle on the dwell meter. Turn the screwdriver clockwise to increase the dwell, or counterclockwise to decrease the dwell.
Instruct your assistant to turn the key off. Tighten the ignition point plate screws. Replace the rotor by hand, or use a screwdriver to tighten in place. Set the distributor cap back onto the distributor and use the appropriate screwdriver to refasten the screws or the small hold-down clamps. Refer to your owner's manual for the proper ignition timing of your engine. For example, it could be 8 or 10 degrees BTD (before top dead center)
Disconnect the vacuum line that attaches to the distributor vacuum advance diaphragm on the side of the distributor. Locate the notch on the crankshaft pulley and the small metal timing tab on the front of the engine block. Use a rag to wipe the small lines and numbers clean on the tab and pulley. Use a socket, extension and ratchet wrench to loosen the distributor hold-down bolt, but only enough so you can move the distributor with mild pressure.
Hook up the red lead of a timing light to the positive terminal on the battery. Hook up the negative lead of the timing light to the negative battery terminal. Place the timing light wire clip on the number 1 spark plug wire (check your repair manual for its location). Have your assistant start the engine. Point the timing light nozzle down at the metal timing tab. Turn the distributor so that the notch in the crankshaft pulley aligns with your correct degree number on the tab, according to your service manual.
Shut the engine off. Tighten the distributor hold-down bolt with the socket, extension and ratchet wrench. Reconnect the vacuum advance line to the distributor. Unhook the timing light leads. You have now set the timing after you have adjusted the points for the proper dwell angle.
- Anytime you change the points setting, you will have to reset the ignition timing with a timing light. If you re-set the timing first, you will not have to adjust the dwell angle on the points.
Things You'll Need
- Allen wrenches
- Dwell meter
- Owner's service manual
- Socket set
- Socket extension (8 to 12 inches)
- Ratchet wrench
- Timing light
Chris Stevenson has been writing since 1988. His automotive vocation has spanned more than 35 years and he authored the auto repair manual "Auto Repair Shams and Scams" in 1990. Stevenson holds a P.D.S Toyota certificate, ASE brake certification, Clean Air Act certification and a California smog license.