How to Check Points With a Dwell Meter
Ignition breaker points describes an older electronic component used in vehicles to send a timed spark from the distributor to the combustion chamber, for the purpose of firing the cylinder. The point contacts open and close, according to their position on the distributor cam as it spins. The gap between the points can be measured in thousandth's of an inch with the use of a feeler gauge, or degrees when checked and measured with a dwell meter. Although a feeler gauge can measure the point gap, a dwell meter is a much more precise method of checking and setting the points.
Other People Are Reading
Things You'll Need
- Screwdrivers
- Owner's service manual
- Allen wrenches (if applicable)
- Assistant
Instructions
-
-
1
Place the vehicle in park or neutral, according to your transmission type. Set the emergency brake. Raise the hood and locate the distributor on your engine. The distributor will be located at the front or rear (topside) of the engine, and will have wires attached to the top of the distributor cap. Use a screwdriver to to turn the two hold-down screws on the distributor cap and pull the cap off and wedge it away from the distributor. If the cap has spring clamps, use a flat-head screwdriver to pry both clamps loose.
-
2
Pull the coil wire from the coil and the middle of the distributor to prevent accidental sparking. Look at the set of points on the distributor plate. It will either have two screws holding the points base, with one of them an adjusting screw and the other as the pivot screw. The adjusting screw has a slot for a flat-head screwdriver; this will open and close the points, adjusting the dwell. The other type of points setup has an Allen screw for opening and closing the points. If it has the Allen adjustment, pre-fit an Allen head tool to it so that you know what size to use.
-
-
3
Set the Allen wrench aside nearby for quick access. Take the red wire lead on a dwell meter and attach it to the negative (-) pole on the ignition coil. The coil will be close to the distributor and look slightly smaller than a pop can. Take the black wire on the dwell meter and attach it to a good ground source on the engine, or clip it to the negative post on the battery.
-
4
Loosen the pivot and adjusting screws on the points with a screwdriver, but do not loosen them all the way -- only enough to allow the lever arm on the points to move with tension. For the Allen head adjustment, place the Allen head tool into the adjusting socket on the points; it should stay there. Turn the face of the dwell meter toward you so you can see the needle position when it moves across the dial and indicates the degrees.
-
5
Refer to your owner's service manual for the dwell specification on your engine. If reads 28 to 32 degrees, it means your optimum degree setting will be 30 degrees dwell. It might also be expressed as 30 degrees +/- 2 degrees. Place a slot screwdriver in the wedge slot on the points arm, or be ready to turn the Allen head too. Have an assistant turn the key to the start position and hold it there while you read the dwell meter. The needle might wobble slightly, but if you stabilize it, the needle will indicate the degrees on the scale.
-
6
Turn the slot screwdriver or Allen tool to advance or retard the degrees until it meets specifications. Let your assistant crank the engine over for only 10 to 12 seconds at a time. Because of this, you will have to make the adjustment rather quickly. After setting the correct dwell, tighten the pivot and adjustment screw on the points base with the screwdriver. Extract the Allen wrench, if you have this type. Place the distributor cap back on and turn the hold-down screws with a screwdriver, or snap the clips back into position. Reconnect both ends of the ignition coil wire to the coil and the distributor cap.
-
7
Instruct your assistant to start the engine. Check the dwell setting again. If the dwell has moved off specifications, perform the same procedure to adjust it. If the distributor cap has an adjustment window on the side, place the Allen tool through the window and adjust the dwell setting while the engine runs.
-
1
References
- Photo Credit Thinkstock Images/Comstock/Getty Images
