Engine Will Not Crank; Starter Motor Spins But Does Not Crank Engine; Starter Motor Spins But Will Not Stop; Engine Cranks Slowly - Generac Power Systems GTH760 Service Manual

GeNerAl INForMATIoN
The starter motor utilizes a solenoid, similar to an automo-
bile starter, to assist in pinion gear engagement. When the
starter motor is activated, the pinion gear engages a ring gear
attached to the engine flywheel and cranks the engine.
Figure 6-1. Starter Motor
TroubleSHooTING
NOTE: If a starting problem is encountered, the engine
itself should be thoroughly checked to eliminate it as
the cause of starting difficulty. It is a good practice to
check the engine for freedom of rotation by removing
the spark plugs and flywheel guard and turning the
crankshaft with a socket and ratchet or breaker bar, to
be sure it rotates freely.
*
wArNING: do NoT roTATe eNGINe wITH eleCTrIC
STArTer wHIle SPArk PluGS Are reMoved uNleSS
uSING A CoMPreSSIoN GAuGe. ArCING AT THe
SPArk PluG eNdS MAY IGNITe THe GASolINe vAPor
eXITING THe SPArk PluG Hole.

ENGINE CRANKS SLOWLY:

a. Additional load affecting performance (see note above).
b. Discharged battery.
c. Faulty electrical connection (battery circuit).
d. Discharged battery (see alternators).
e. Dirty or worn starter motor commutator, bearing, weak
magnets, etc.
f. Worn brushes or weak brush spring.
g. Wrong oil viscosity for temperature expected.
h. Battery leads too long or wire too small.
i. Battery too small.

ENGINE WILL NOT CRANK:

a. Faulty safety interlocks.
b. Discharged or defective battery.
c. Faulty electrical connections.
d. Faulty starter motor switch (open circuit).
e. Open circuit in starter motor.
f. Brushes sticking, etc.
g. Faulty solenoid.

STARTER MOTOR SPINS BUT DOES NOT CRANK ENGINE:

a. Sticking pinion gear due to dirt.
b. Damaged pinion or ring gear.
c. Battery faulty or damaged.
d. Incorrect rotation due to reversed motor polarity – all motors
rotate counterclockwise viewed from pinion gear.
e. Damaged solenoid

STARTER MOTOR SPINS BUT WILL NOT STOP:

a. Defective starter switch.
b. Solenoid stuck engaged.
TeST equIPMeNT
DIGITAL MULTIMETER:
A digital multimeter (VOM) may be used to read volts, ohms,
amperes and test diodes (rectifiers), Figure 6-2.
NOTE: The Digital Multimeter is equipped with two
fuses to prevent damage to the meter in the event that
the input limits are exceeded. If the meter displays a
reading of 0.00 when testing DC output, check fuses in
meter. Refer to VOM operators manual for procedure
for checking fuses.
Figure 6-2. Digital Multimeter
6-1

SeCTIoN 6: eleCTrIC STArTer

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