Ignition System Troubleshooting - Cessna 177 SERIES Service Manual

11-56. TROUBLE SHOOTING.
TROUBLE
PROBABLE CAUSE
REMEDY
0
ENGINE FAILS TO START.
Defective ignition switch.
Check switch continuity.
Replace
if defective.
Spark plugs defective, improperly
Clean, regap and test plugs.
gapped or fouled by moisture or
Replace if defective.
deposits.
Defective ignition harness.
If no defects are found by a
visual inspection, check
with a harness tester.
Re-
place defective parts.
Magneto "P" lead grounded.
Check continuity.
"P" lead
should not be grounded in the
ON position, but should be
grounded in OFF position.
Repair or replace "P" lead.
Failure of impulse coupling.
Impulse coupling pawls should
engage at cranking speeds.
Listen for loud clicks as impulse
couplings operate.
Remove
magnetos and determine cause.
Replace defective magneto.
Defective magneto.
Refer to paragraph 11-63.
Broken drive gear.
Remove magneto and check mag-
neto and engine gears. Replace
defective parts.
Make sure no
pieces of damaged parts remain
in engine or engine disassembly
will be required.
ENGINE WILL NOT
Spark plugs defective, im-
Clean, regap and test plugs.
IDLE OR RUN PROPERLY.
properly gapped or fouled
Replace if defective.
by moisture or deposits.
Defective ignition harness.
If no defects are found by a
visual inspection, check with
a harness tester.
Replace
defective parts.
Defective magneto.
Refer to paragraph 11-63.
Impulse coupling pawls
Listen for loud clicks as impulse
remain engaged.
coupling operates. Remove
magneto and determine cause.
Replace defective magneto.
Spark plugs loose.
Check and install properly.
11-20 Change 2