operation, you must exercise care and follow correct
from the distributor connection of the coil to ground.
procedures.
With the ignition switch on and the points closed,
voltage drop should not exceed 6.9 volts. If the drop
DISTRIBUTOR.--You can replace breaker
exceeds 6.9 volts, a high resistance exists in the resistor,
points with the distributor installed. However, it is
ignition switch, or the wiring between the battery and
usually better to remove the distributor from the engine.
the coil. A drop of less than 4.5 volts indicates a shorted
This gives you easier access to the breaker points. It
resistor.
also enables you to inspect and repair other components
in the distributor.
Starting Ignition Circuit Test.--Connect the
voltmeter as shown in figure 6-48, view B. Remove the
With the distributor cap removed, scribe a line
secondary coil wire from the distributor cap and ground
across the junction of the distributor housing and the
the wire. With the ignition switch off, crank the engine
engine block. Scribe another line on the distributor
by placing a jumper wire from the battery positive post
housing in line with the center of the rotor contact strip.
to the S terminal of the starter solenoid or relay. The
These lines mark the relative positions of the parts,
voltage drop should not exceed 0.1 volt. If the drop
which will facilitate reassembly.
exceeds 0.1 volt, a high resistance exists in the starter
Disconnect the primary lead and the vacuum
advance vacuum line. Remove the distributor from the
engine. Clamp the distributor in a soft-jawed vise. Take
Coil-to-Ground Test.--Connect the voltmeter as
care not to damage the drive gear or housing.
shown in figure 6-48, view C. With the ignition switch
Before you attempt to remove the breaker points
on and the points closed, the voltage drop should not
(with the distributor on or off the engine), stuff small
exceed 0.1 volt. If the drop exceeds 0.1 volt, a high
rags in any hole or opening in the breaker plate through
resistance exists either in the coil-to-distributor
which small screws or nuts may fall. Note the location
wire, the engine-to-frame ground strap, the
and position of the primary lead-in and condenser wires
distributor-to-engine mounting, or in the breaker
before disconnecting them.
points. When you isolate the malfunction to one area,
continue testing that area.
Remove the used points. Thoroughly clean the
mounting area and the breaker cam, and install the
If you have not located the malfunction after you
replacement points.
make these tests, remove the coil, resistor, and
condenser and test them separately.
The condenser is generally replaced at the same
time the points are replaced. However, if the condenser
SECONDARY CIRCUIT TESTS.--If pre-
is to be reused, it should be tested for capacity,
liminary testing indicates that the malfunction is in the
resistance, and leakage. If a new condenser is used, it
secondary circuit, the defect can be located by making
should also be tested. Compare the results to the
the following tests.
manufacturer's specifications for the equipment at
Test 1.--Use a megger and follow the instructions
hand.
provided with it. Test the distributor cam, rotor, and
With the points and the condenser installed, rotate
spark plug leads for insulation breakdown, cracks, or
the breaker cam until the points close. Check the
opens.
alignment of the contacts. If both contacts are flat, the
Test 2.--Remove and thoroughly examine the
entire surface should contact at the same time. If both
spark plugs. A plug that exhibits any of the conditions
contacts are convex or if one is flat and the other
shown in figure 6-49 (except F, G, and H) may be
convex, contact should be in the center. If alignment is
reconditioned and reused. A plug exhibiting any of the
incorrect, bend the stationary contact bracket to provide
conditions in F, G, or H must be replaced. The cause for
correct alignment.
the damage must also be corrected.
NOTE: Never attempt to align the points by
bending the movable arm.
Repair and Adjustment
The point gap is the amount of opening between the
The repairs and adjustments required on a battery
contacts when the points are fully opened by the
ignition system are comparatively simple to perform.
breaker cam. This is a critical area and must be closely
To achieve good equipment performance and economic
set. If the gap is too small, the points arc and burn; if the
6-44
