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TestNumberi6--initia]
ignition Timing
This test should be made following any dwell adjustments as the point
setting controls the basic ignition timing.
On electronic ignition
systems refer to the vehicle service manual for special instruction_.
Spark
timing controls are used to advance or retard timing.
Follow manufacturer's
service procedures to check & adjust timing properly.
I.
Connect a timing light to the battery and #i spark plug cable as_illustrated
below, in Fiqure 38.
2.
Rotate the Function Selector Switch to the RPM position and set the RPM
range selector to the Lo-1200 RPM position for idle speeds and the Hi-6000
RPM for the high speed tests.
3.
Locate the timing mark on the fly wheel and degree indicator plate.
Clean both surfaces and apply
a white chalkmark on the fly wheel mark
for good vlsibility.(Figure 35)
4.
Consult your vehicie service manual or tune-up decal under the hood
to determine which, if any vacuum hoses must be removed for proper
timing adjustment.
Make sure to follow all timing instructions
pertaining to your vehicle.
The above illustration shows the vacuum
advance hose disconnected and plugged.(Figure 37)
5.
Close starter shunt, start the engine and operate at specified engine
speed.
Refer to vehicle tune up specifications label under the hood
for proper RPM.
6.
Operate timing light and aim it at the timing mark.
Note the position of the
fly wheel mark in relation to the degree indicator.
Compare to specified
initial timing.
If not within specifications, readjust distributor as
required,
7.
TIMING ADJUSTMENT.
To change timing, loosen the d_stributor hold down
screw or bolt and rotate the distributor body as shown in Figures
36 and 37. until proper timing is indicated.
Test Number 17--TimingAdyanceSystems
NOTE:
The following centrifugal and vacuum advance tests are general
ones and may not apply to many of.the more modern vehicles.
Many of today's
vehicles have complex emission and ignition control systems which may alter
or prevent spark advance from taking place under various conditions.
It
is therefore very important to consult your vehicle service manual for
the proper procedures to check and/or repair advance systems.
Ao
Mechanical
CENTRIFUGAL ADVANCE.
With the distributor vacuum hose disconnected and
plugged, operate the engine at specified idle speed and note position
of timing mark.
INCREASE engine RPM slowly and observe movement of timing
mark.
The mark should move steadily and without jerking in the opposite
direction tO fly wheel rotation, up to approximately 1800 RPM.
Decrease
speed and mark should return smoothly to its original position.
VACUUM ADVANCE TEST.
Operate the engine at 1500 RPM and connect the vacuum
advance hose to the distributor vacuum control and observe movement of
the timing mark.
The mark should move opposite to fly wheel rotation
and may appear beyond the range of the degree indicator with a normal
operating
vacuum control.
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