condenser and to ground. The meter should register slightly and then return to infinity (maximum resistance). Any continuous reading other than infinity indicates that the condenser is leaking and must be replaced.
Installing contact points is a relatively simple procedure but must be done with precision and care in order to achieve good engine performance and economy. Make sure the points are clean and free of any foreign material.
Proper alignment of the contact points is extremely important (fig. 2-52). If the faces of the contact points do not touch each other fully, heat generated by the primary current cannot be dissipated and rapid burning takes place. The contacts are aligned by bending the stationary contact bracket only. NEVER BEND THE MOVABLE CONTACT ARM. Ensure the contact arm-rubbing block rests flush against the distributor cam. A small amount of an approved lubricate should be placed on the distributor cam to reduce friction between the cam and rubbing block. Once the points are installed, they can be adjusted using either a feeler gauge or dwell meter.
To use a feeler gauge to set the contact points, turn the engine over until the points are FULLY OPEN. The rubbing block should be on top of a distributor cam lobe. With the points open, slide the specified thickness feeler gauge between them. Adjust the points so that there is a slight drag on the blade of the feeler gauge. Depending upon point design, use a screwdriver or Allen wrench to open and close the points. Tighten the hold-down screws and recheck the point gap. Typically point gap settings average around .015 inch for eight-cylinder engines and .025 inch for six- and four-cylinder engines. For the gap set of the engine you are working on, consult the manufacturer's service manual.
Figure 2-52. - Contact point alignment.
Ensure the feeler gauge is clean before inserting it between the points. Oil and grease will reduce the service life of the points.
To use a dwell meter for adjusting contact points, connect the red lead of the dwell meter to the distributor side of the ignition coil (wire going to the contact points). Connect the black lead to ground.
If the distributor cap has an adjustment window, the points should be set with the engine running. With the meter controls set properly, adjust the points through the window of the distributor cap using a Allen wrench or a special screwdriver. Turn the point adjustment screw until the dwell meter reads within manufacturer's specification. However, if the distributor cap does not have an adjustment window, remove the distributor cap and ground the ignition coil wire. Then crank the engine; this action will simulate engine operation and allow point adjustment with the dwell meter.
Dwell specifications vary with the number of cylinders. An eight-cylinder engine requires 30 degrees of dwell. An engine with few cylinders requires more dwell time. Always consult the manufacturer's service manual for exact dwell values.
Dwell should remain constant as engine speed increases or decreases. However, if the distributor is worn, you can have a change in the dwell meter reading. This is known as DWELL VARIATION. If dwell varies more than 3 degrees, the distributor should either be replaced or rebuilt. Also, a change in the point gap or dwell will change ignition timing. For this reason, the points should always be adjusted before ignition timing.
ELECTRONIC IGNITION DISTRIBUTOR SERVICE. - Most electronic ignition distributors use a pickup coil to sense trigger wheel rotation and speed. The pickup coil sends small electrical impulses to the ECU. If the distributor fails to produce these electrical impulses properly, the ignition system can quit functioning.
A faulty pickup coil will produce a wide range of engine troubles, such as stalling, loss of power, or not starting at all. If the small windings in the pickup coil break, they will cause problems only under certain conditions. It is important to know how to test a pickup coil for proper operation. 2-41Continue Reading