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Ignition System
2-04
Dwell Angle Check
1. Disconnect the distributor and plug the vacuum line. Connect
the tester.
2.
Turn the test control knob to the set position.
3.
Adjust the set control knob until the needle on the dwell meter
lines up with the set line.
4.
Start the engine and let it idle.
5.
Turn the cylinder selector to the figure corresponding
to the
number of lobes on the cam of the distributor.
6.
Read the dwell angle on the dwell meter and compare the
reading to specifications.
7.
Turn off the engine.
8. If the dwell angle was below the specified amount, the breaker
point gap is too wide. If the dwell angle was above the
specified amount, the breaker point gap is too close.
If the dwell is to specifications,
turn the test selector knob to the
OFF position and disconnect the tester leads and jumper wire, then
connect the distributor vacuum line.
Initial Timing Check
Manually turn engine to locate timing notch on crankshaft
pulley and, using a piece of chalk, highlight
notch (Figure 7).
Connect timing light to engine as per manufacturer' s
instructions,
start engine and allow to idle at specified idle speed. Disconnect
and plug vacuum hose and check ignition timing. Refer to specifi-
cations. Adjust as required.
Do not disconnect timing light or reconnect vacuum hose at this
stage.
Distributor Spark Advance Test
To carry out ignition advance checks, the timing light must be
of the type that includes an advance meter.
With timing light still connected,
restart engine and hold at
2000 rpm. Adjust timing light to bring crankshaft notch back to
initial timing mark and note mechanical
advance on timing light
meter. Reconnect vacuum advance hose and adjust timing light to
bring crankshaft notch back to initial timing mark. The meter will
measure total advance. To obtain a vacuum advance figure, sub-
tract mechanical advance figure from total.
When investigating
ignition problems a more detailed check of
the advance characteristic
may be required at varying engine rpm
and vacuums. This can be done with a tachometer
and vacuum
pump*
1. Connect pump directly to distributor
(Figure 8).
2.
Start engine and adjust idle to 1000 rpm.
3. Adjust timing light to bring crankshaft notch back to TDC and
note mechanical
advance.
4.
Pump vacuum to required figure (refer to specifications),
readjust timing light and note advance.
To calculate vacuum advance,
subtract mechanical
advance
obtained in step 3 from total advance obtained in step 4.
5. Repeat step 4 at varying vacuum figures.
6.
Remove vacuum pump and check mechanical
advance at
varying engine i-pm.
Figures quoted in the Specification
Section do not include the
initial static advance.
7.
Reconnect vacuum advance hose.
FIG.
7
Timing Marks
A -
T.D.C. Notch on Crankshaft
Pulley
B -
Timing Marks on Front Cover
FIG. 8
Vacuum Pump Connected
to Distributor
ADJUSTMENTS
Accurate ignition system adjustments are of great importance in
the proper operation and performance
of the engine.
After any adjustment
of ignition timing and distributor point
dwell,
check the distributor
automatic
advance
for proper
operation.
Breaker Point Alignment
The breaker points must be accurately
aligned
and stroke
squarely to assure normal breaker point life. Misalignment
of
these breaker point surfaces can cause premature wear, overheat-
ing and pitting.
1. Turn the cam so that the breaker points are closed, then check
the alignment of the points.
2.
Using a tool and exerting
very light pressure,
align the
stationary point bracket.
Do not bend the movable
arm.
3.
After the breaker points have been properly aligned, adjust the
breaker point gap.
Dwell Angle/Breaker Point Gap Adjustment
Check and adjust dwell angle (breaker point gap) as follows:
1. Connect a dwell meter to engine as per manufacturer' s
in-
structions and start engine.
2.
Record dwell angle at idle and at 2,000 rpm. Check dwell
angle and variation in the Specification
Section.
3. To adjust, stop engine, remove distributor cap and position to
one side, remove rotor.
4.
With ignition on, crank engine with starter. Loosen retaining
screw and adjust breaker points. Tighten retaining screw.
5.
Recheck dwell at idle and 2,000 rpm.
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