JLG 660SJ ANSI Service Manual - Manual (Page 114)

SECTION 3 - CHASSIS & TURNTABLE
3-60 – JLG Lift – 3120718
If steps 1a. thru 1e. can be accomplished as described,
the Governor is probably OK. It recognizes underspeed,
overspeed, onspeed and is not binding internally.
If the above steps cannot be accomplished satisfactorily,
there is probably an actual Governor malfunction.
2. Installation and adjustment problems.
a. Governor is unable to move fuel system freely
(not enough Actuator force available). If Gover-
nor doesn’t move fuel system to on far enough
to provide sufficient fuel but Governor arm
moves far enough when disconnected look for:
1.Linkage binding or misadjusted.
2.Low voltage at Governor during operation.
*Measure the voltage as discussed previ-
ously and observe voltage during operation.
If Governor fails to move full on and voltage
dips over 1 volt, check for undersize wire
(should be #16 minimum).
3.Excessive forces at Governor during running,
particularly on carburetor engines.
*Carburetor butterfly valves are loaded by
engine vacuum during running, which can
add considerable force not present when
engine isn’t running.
*Springs in the system; carburetor return
springs, acceleration pump springs, etc., are
not usually needed and can cause governing
problems.
b. Governor is unstable at light-load or no-load.
See “Linkage” for carbureted engines.
c. Governor experiences sudden, momentary
spikes toward max. at random intervals, then
recovers.
1.Look for loose wiring or momentary shorts in
wiring.
2.Noise or occasionally missing speed signal.
d. Speed seems to slowly wander (5-15 second
periods) around at speed, particularly at higher
loads. See item 2a. 3 concerning excessive on
Governor.
3. Governor not tuned or adjusted for engine/applica-
tion.
The basic adjustment to set sensitivity/stability is the
Gain pot. A good starting point for many engines is
full CCW, then CW 1/3 turn. (See “Governor adjust-
ment” section). To increase stability, turn CCW. If sat-
isfactory governing cannot be achieved with this one
adjustment, the factory adjustment may be needed.
Normal starting point for this adjustment is fully
CCW, then CW 1/4 turn. (Before changing this pot,
mark the original position).
NOTE: If problems occurs with the Governor overshooting
when a large load is released from the engine, such
as driving up a hill and stopping. There is usually
one of two things:
a. Gain adjustment is to far CCW.
b. Mechanical preload between the carburetor and
actuator is to large, this should be no greater
than 1/2 to 1 ball dia. (Ref. to page 43 par. 1).