Check Ignition - Generac Power Systems GTV99O Service Manual

SECTION
.I: GENERAL INFORMATION
SYSTEMATIC CHECKi
lf the engine will not stad and the cause of malfuncrion is
not €adilyapparen! perform a systematic
check in the fo lowing
orderl
1. lgnition
2. Fuel
3. Compression
This check'up, performed in a systematic manneri cdn usu-
ally be done in a matter of minutes. lt isthe quickest and surest
method of determining the cause of fiilure. The basiccheckup
procedure isthe same for all engine modeh, while any varia-
tion, by model, wiilbe shown underthe subject heading.
CHECK IGNITION:
lf spark does not occur look for:
.
Shorted ignition,kill wlre
.
Two cosed diodes in ground wire harness
.
Incorrect a rmature air gap
FIECK lGNnoN {ENG NE RUNNING)I
ifengine runs but misses during operation. a quick check to
determine if ignition is or is not at fault can be made by
installing a spa* tesler (Generac p,t\l OC5969) between the
spark plug lead and each spark plug, Figure t-6. A spark mks
will be rcadily apparent when the engine is running. tf spark
i5 good but engine misses, check for a fouled spark plL'lg.
CHECK ]GNITION
(FOULED
PLUG OR OTHER CAUSES):
To check for a fouled spark plug or a nonjunctioning cylin-
der. attach the lpark tener (Generac P/N OC5969)between
the
spark plug lead and each spark plug. Stad and run engine at
top no lo.d speed. Now ground one spark plug, Fig! re t -7. The
engineshould
continue to run on the other cylinder Repeatthis
test with the other cylnder lf the engine will not continue to
run when making thistest, the cylinder that ls NOT grounded
is not functioning and/orthe spark plug is fouled. Installa new
spa* plug before prcceeding. f miss cont n!es, problem may
be carburetion orcompression.
See Check Calburction, Check
Compression. Also see Cy inder BalanceTest.
Figvre 1-7. Checking fot Fouled plugs
CYL NDER EAIANCE TEST
lf the enqine is hard stadinq, runs rough, misses or tacks
power, pertorm a cylinder balance test to determirre wnerner
boih cylirdes are ope.ai 19 rc trerr fL lporenlrat.
Tools Requircdi
1. Two gnition Teste6 (Cenerac P/N OC5969)
Attach an i9nition tester betwe€n the spark plug lead and
each spark plug, Fiqure 1'6.
Stadand run engine runnln9 attop no load speed and note
spark at ign lion teste6. lf the spa.k is equat at both jgniUon
testers, the problem is not igniton related. A spark miss will
be readily apparent. Now note RPM of engine. Ground out one
cylinder by contacting ignition tester and a good grcund on
engrne, Figufel 8. Note RPM loss. Then ground out the other
spark p ug and note ihe RPNI loss. lf the difference between
the two cylind€rs does not exceed 75 RPNI, the amount ofwork
the two qlinde|s are doing should be considered equal.
figwe 1-6. Running Check
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