Toyota Corolla 1970-1987 Repair Guide

Dwell Angle

Print

See Figure 1

The dwell angle is the number of degrees of distributor cam rotation through which the points remain closed (conducting electricity). Increasing the point gap decreases dwell, while decreasing the gap increases dwell.

The dwell angle may be checked 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 meter will fluctuate between 0 dwell and the maximum figure for that setting. Never attempt to adjust the points when the ignition is ON , or you may receive a shock.



Click image to see an enlarged view

Fig. Fig. 1: Dwell as a function of point gap

On cars with a fully transistorized electronic ignition (1978 and later vehicles without points), the dwell is pre-set at the factor and is not adjustable

ADJUSTMENT WITH A DWELL METER

See Figure 2

  1. Connect a dwell meter to the ignition system, according to the tool manufacturer's instructions but keeping in mind the following points:
    1. When checking the dwell on a conventional ignition system, connect one meter lead (usually black) to a metallic part of the car to ground the meter; the other lead (usually red) is connected to the coil primary post (the one with the small lead which runs to the distributor body);
    2.  
    3. When checking dwell on a model with transistorized ignition, ground one meter lead (usually black) to a metallic part of the car; hook up the other lead (usually red) to the negative (-) coil terminal. Under no circumstances should the meter be connected to the distributor or the positive (+) side of the coil. (Please refer to the preceding service precautions).

      Click image to see an enlarged view

      Fig. Fig. 2: Dwell meter connections with a transistorized point ignition

    4.  

  2.  
  3. If the dwell meter has a set line, adjust the needle until it rests on the line.
  4.  
  5. Start the engine. It should be warmed up and running at the specified idle speed.
  6.  

It is not necessary to check the dwell on the transistorized system for certain 1977 California models. It is set at the factory and requires no adjustment. If in doubt, check the Vehicle Emission Control Information (VECI) label located in the engine compartment


CAUTION
Be sure to keep fingers, tools, clothes, hair, and wires clear of the engine fan. The transmission should be in Neutral (or Park), parking brake set, the drive wheels blocked and the vehicle should be in a well ventilated area

  1. Check the reading on the dwell meter. If your meter doesn't have a 4-cylinder scale, multiply the 8-cylinder reading by two.
  2.  
  3. If the meter reading is within specification (refer to the Tune-Up Specifications chart), shut the engine OFF and disconnect the dwell meter.
  4.  
  5. If the dwell is not within specifications, shut the engine OFF and adjust the point gap as previously outlined. Increasing the point gap decreases the dwell angle and vice versa.
  6.  
  7. Adjust the points until dwell is within specifications, then disconnect the dwell meter. Adjust the timing as detailed in the following section.
  8.  

 
label.common.footer.alt.autozoneLogo