Dwell Variation Test - Sears 161.2161 Owner's Manual

DWEll VARIATION TEST
Check the owners manual or engine compartment
decal. Follow instructions regarding vacuum line
or advance-retard solenoid connections. Vacuum
line must be disconneded from distributor.
Increase the engine speed from idle to a minimum
of 1500 RPM and then reduce it back to idle.
Watch the dwell reading during this procedure.
If the dwell variation is more than 3 degrees, check
for wear in the breaker plate or wear in the distri-
butor shaft or bush ings •
IDLING SPEED AND CARBURETOR ADJUSTMENT
Start the engine and turn the idle speed screw
unti I specified idling speed is indicated.
x100
14
(See owners manua I).
On engines without exhaust emmission control sys-
tems, turn the idle mixture screw in (lean) unti I
the idling speed starts to decrease, then turn it
back out (rich) just until the idling speed reaches
a maximum. Further richening past this point will
only-wos-te
ftte~. lh-ts--s-heul~done
slewly to al
low eng i ne speed to stab iii ze •
NOTE: On multi-barrel carburetors, repeat this
procedure on each idle mixture screw until the
highest idling speed and smoothest operation is
obtained. If the engine idle speed is now higher
than the manufacturer's specification, turn the
throttle idling adjustment screw unti I the speci-
fied idling speed is indicated and readjust the
mixture screws with the above procedure.
TYPICAL CARBURETORS
10 12
B
o
RPM
x100
SOLIO
Connect the test leads as shown in FIGURE 1. Set
the slide switch knob to aT HER TESTS and the
Function Selector Knob to the RPM position that
corresponds to the number of cylinders in the
engine being tested.
.---0
serve-tne test readings onthe RPM x 100
scale.
The engine should be at normal operating temper-
ature for this test. Many cars built in 1970 and
later have idle mixture screw limiter caps that
restri ct adjustment. On these cars the carburetor
should be adjusted according to the procedure in
the manufacturer's service manual.
NOTE: On engines equipped
with exhaust emission control
systems, air injection pumps
and positive crankcase ventila-
tion, refer to the decal in
the engine compartment or the
owners manual for idle adjust-
ment specifications.
IDLE MIXTURE SCREWS
IDLE SPEED SCREW ... - ---------.....--------------------4