Briggs & Stratton 272147 Repair Manual page 19

Check Ignition (With Engine Starter)
With spark plugs installed, attach a
to each spark plug lead and ground the other end of the
tester as shown in Fig.12. Activate the electric starter. If
spark jumps the tester gaps, you may assume the
ignition system is functioning satisfactorily.
Fig. 12
NOTE
: Engines equipped with Magnetron®
ignition system will still display spark at tester
with a partially or fully sheared flywheel key. A
partially sheared flywheel key will affect ignition
timing and engine performance.
If spark does not occur look for:
1. Improperly operating interlock system
2. Shorted equipment stop switch wire
3. Two closed diodes in ground wire harness (see:
Troubleshooting Ground Wire Harness)
4. Incorrect armature air gap
5. Armature failure
Page 14
Check Ignition (Engine Running)
ignition tester If engine runs but misses during operation, a quick check
#19368
to determine if ignition is or is not at fault can be made by
installing Tool
and each spark plug, Fig.13. A spark miss will be readily
apparent when the engine is running. If spark is good but
engine misses, check for a fouled spark plug.
Fig. 13
Check Ignition (Fouled Plug or Other Causes)
To check for a fouled spark plug or a non-functioning
cylinder, attach Tool
plug lead and each spark plug. With engine running at
top no load speed, ground one spark plug, Fig. 14. The
engine should continue to run on the other cylinder.
Repeat this test with the other cylinder. If the engine will
not continue to run when making this test, the cylinder
that is NOT grounded is not functioning and/or the spark
plug is fouled. Install a new spark plug before
proceeding. When replacing spark plugs always use
Briggs & Stratton
TM
Vanguard Twin-Cylinder OHV Liquid-Cooled Engine
tester between the spark plug lead
#19368
tester between the spark
#19368
#491055 or #496018
Section 2 - Troubleshooting
.