Cessna 1969-1976 172 Series Service Manual page 155

11-9. TROUBLE SHOOTING (Cont).
~
TROUBLE
ENGINE STARTS BUT
DIES, OR WILL NOT
IDLE. (Cont. )
PROBABLE CAUSE
REMEDY
-~~
Vaporized fuel. (Most likely
to occur in hot weather with
a hot engine.
Refer to paragraph 11-79.
Induction air leaks. Check visually. Correct the
cause of leaks.
Manual primer leaking. Disconnect primer outlet line.
If fuel leaks through primer,
repair o r replace p r i m e r .
Leaking float valve or float
level s e t too high.
Perform an idle mixture check.
Attempt to remove any rich
indication with the idle mixture
adjustment. If the rich indica-
tion cannot be removed, the
float valve is leaking or the
float level is set too high. Re-
place defective parts, r e s e t
float level.
~ ~~~~~ ~~~
If engine will
start
when primed
but stops when priming is dis-
continued, with mixture control
in full RICH position, the carbu-
r e t o r is defective. Repair or
replace carburetor.
Defective carburetor.
Defective engine.
Check compression. Listen for
unusual engine noises. Engine
repair is required.
ENGINE RUNS ROUGHLY
OR WILL NOT ACCELERATE
PROPERLY.
Restriction in aircraft fuel
system.
Refer to Section 12.
Worn
or
improperly rigged
throttle
o r mixture control.
Check visually. Replace worn
Linkage. Rig properly.
Remove, clean and regap plugs.
Replace i f defective.
Spark plugs fouled or im-
properly gapped.
~~
Defective ignition system.
Refer to paragraph 11-58.
~~ ~ ~~~ ~~ ~
Defective
or
badly adjusted
accelerating pump in carbu-
retor.
Check setting of accelerating
pump linkage and adjust as
necessary.
Float level set too low. Check and r e s e t float level.
Defective carburetor.
If engine will
start
when primed
but stops when priming is dis-
continued, with mixture cont r ol
in full RICH position, the carbu-
r e t o r
is
defective. Repair
or
replace carburetor.
Defective engine. Check compression. Listen for
unusual engine noises. Engine
repair
is
required.
Change 3 11-5