1970-74 Models and Canadian B21A Engine
See Figure 1
Volvo recommends that the breaker points be inspected and adjusted every six months or 6000 miles (9662 km). If, upon inspection, the points prove to be faulty, they must be replaced with the condenser as unit.
Remove the distributor cap and rotor from the top of the distributor, taking note of their placement. On fuel-injected six-cylinder models, remove the breaker point protective cover. Place a screwdriver against the breaker points and examine the condition of the contacts. Replace the points if the contacts are blackened, pitted, or worn excessively, if the breaker arm has lost its tension, or if the fiber rubbing block on the breaker has become worn or loose. Contact points that have become slightly burned (light gray) may be cleaned with a point file.
To replace the points and condenser, disconnect the electrical leads for both at the primary connection. Remove the lockscrew for the contact breakers and lift them straight up. Loosen the condenser bracket retaining screw and slide out the condenser. While the points are out, lubricate the breaker cam with a very light coating of silicone-based grease. Clean the distributor base plate with alcohol to free it of any oil film that might impede completion of the ground circuit. Also clean the contact point surfaces with the solvent. Install the new points and new condenser and tighten their retaining screws. Connect the electrical leads for both at the primary connection. Make sure that the point contacts are aligned horizontally and vertically. If the points are not aligned properly, bend the stationary arm as necessary.
The breaker points must be correctly gapped before proceeding any further. Turn the engine until the rubbing block on the point assembly is resting on the high point of the distributor cam. Loosen the hold-down screw lightly and insert a feeler gauge of the proper thickness between the point contacts. Fine adjustment is made by inserting a screwdriver into the adjusting recess and turning the screwdriver until the proper size feeler gauge passes between the point contacts with a slight drag. Without disturbing the setting, tighten the breaker point retaining screw.
If a dwell meter is available, proceed to Dwell Angle Adjustment. A dwell meter is considered a more accurate means of measuring point gap. If the meter is not available, except on fuel-injected six-cylinder models, proceed to replace the rotor on top of the distributor shaft, making sure that the tab inside the rotor aligns with the slot on the distributor. Before replacing the rotor on fuel-injected six-cylinder models, install the breaker point protective cover. Place the distributor cap on top of the distributor, make sure it is properly seated, and snap the cap clasps into the slots on the cap. Make sure that all the spark plug wires fit snugly into the cap. Proceed to the Ignition Timing Adjustment.
It is not possible to set the dwell on electronic ignition systems, although it is possible to measure it.Adjustment
1970-74 MODELS AND CANADIAN B21A ENGINES
The dwell angle is the number of degrees of distributor cam rotation through which the breaker points remain fully closed (conducting electricity). Increasing the point gap decreases dwell, while decreasing the point gap increases dwell.
Using a dwell meter, connect the red lead (positive) of the meter to the distributor primary wire connection on the positive (+) side of the coil, and the black lead (negative) wire of the meter to a good ground on the engine (such as a thermostat housing nut).
The dwell angle may be checked either with the distributor cap and rotor installed and the engine running, or with the cap and rotor removed and the engine cranking at starter speed. The meter gives a constant reading with the engine running. With the engine cranking, the reading will fluctuate between zero degrees dwell and the maximum figure for that angle. While cranking, the maximum figure is the correct one for that setting. Never attempt to change dwell angle while the ignition is ON ; touching the point contacts or wire connection with a metal screwdriver while the ignition is ON may result in a nasty shock.
To change the dwell angle, loosen the point retaining screw slightly and make the approximate correction. Tighten the retaining screw, then test the dwell with the engine cranking. If the dwell appears to be correct, install the breaker point protective cover, if so equipped, the rotor and distributor cap, and test the dwell with the engine running. Take the engine through its entire rpm range and observe the dwell meter. The dwell should remain within specifications at all times. Great fluctuation of dwell at different engine speeds indicates worn distributor parts.
Following the dwell angle adjustment, the ignition timing must be checked. A 1° increase in dwell results in the ignition timing being retarded 2° and vice versa.