Briggs & Stratton 272147 Repair Manual page 20

TM
Vanguard Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
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
test the ground wires. The following test will be made
with the meter in the "Diode Test Position".
is recommended to
#19464
DIODE FAILURE DIAGNOSTIC TABLE
Ground Wire Harness
Diode
Equipment
Switch
SWITCH ON SWITCH OFF
Engine runs on one
Shuts Off OK
cylinder.
Engine runs.
Only one cylinder shuts Off
(Both Cylinders)
Won't Run
(No Spark)
Engine runs.
Engine won't shut Off
(Both Cylinders)
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 test lead into receptacle in meter.
RED
2. Insert test lead into receptacle in meter.
BLACK
3. Rotate selector to
4. Insert test lead into ground wire terminal
RED
(brown wire) receptacle in engine harness,
Fig. 16. Leave attached for remainder of test.
5. Touch test lead probe to ground wire tab
BLACK
terminal on ignition coil for #2 cylinder.
Diode
OFF
ON
CAUSE
1 Closed Diode
1 Open Diode
2 Closed Diodes
2 Open Diodes
(Diode Test) position.
Page 15