Vanguard
TM
Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
Page 15
Fig. 14
If miss continues:
The problem may be carburetion or compression related.
See Check Carburetion and/or Cylinder Balance Test
and Cylinder Leakdown Test.
Troubleshooting Ground Wire Harness
The ground wire harness contains two diodes. If a diode
fails “open,” the cylinder with the open diode will continue
to run when the equipment key switch is turned off. If a
diode fails “short,” the cylinder with the shorted diode will
not run (no spark).
Refer to Failure Diagnosis Table for symptoms.
Testing Ground Wire Harness
The Digital Multimeter, Tool
#19464 is recommended to
test the ground wires. The following test will be made
with the meter in the “Diode Test Position”.
Fig. 15
In the Diode Test position, the meter will display the
forward voltage drop across the diode(s). If the voltage
drop is less than 0.7 volts, the meter will “Beep” once as
well as display the voltage drop. A continuous tone
indicates continuity (shorted diode). An incomplete
circuit (open diode) will be displayed as “OL.”
1. Insert
RED test lead into receptacle in meter.
2. Insert
BLACK test lead into receptacle in meter.
3. Rotate selector to (Diode Test) position.
4. Insert
RED test lead into ground wire terminal
(brown wire) receptacle in engine harness,
Fig. 16. Leave attached for remainder of test.
5. Touch
BLACK test lead probe to ground wire tab
terminal on ignition coil for #2 cylinder.
DIODE FAILURE DIAGNOSTIC TABLE
Ground Wire Harness
DiodeDiode
OFF
ON
Equipment
Switch
SWITCH ON
SWITCH OFF CAUSE
Engine runs on one
cylinder.
Engine runs.
(Both Cylinders)
Won’t Run
(No Spark)
Engine runs.
(Both Cylinders)
Shuts Off OK
Only one cylinder shuts Off
Engine won’t shut Off
1 Closed Diode
1 Open Diode
2 Closed Diodes
2 Open Diodes
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