John-deere stx38 User Manual download pdf (Page 114)

4 - 30

3/21/97

CIRCUIT OPERATION AND DIAGNOSIS

ELECTRICAL

CRANKING CIRCUIT OPERATION

STX38 (SN 210001— ) & STX46

Function:

The cranking system is used to energize the starting

motor.

Operating Conditions:

In order to crank the engine; the key switch must be in

the START position, the PTO switch must be OFF, and

the brake must be ENGAGED. The operator DOES

NOT have to be on the seat to crank the engine.

Theory of Operation:

The starting motor has a separate starter solenoid.

Current flows from the battery (G1) positive terminal to

the starter solenoid (K1), fusible link (F1), and key

switch (S1). With the key switch in the START position,

current flows to the PTO switch (S2) and the optional

fuel shut-off solenoid (Y2), causing the solenoid

plunger to unseat and allow fuel to flow into the venturi

of the carburetor.

The PTO switch (S2) is used in the neutral start circuit

to prevent the engine from cranking IF the PTO switch

is ENGAGED. When the PTO switch is OFF (PTO

disengaged), current flows to the brake switch (S3).

The brake switch (S3) is located under the right side of

the chassis and aligned with the brake pedal bell crank.

When the brake pedal is in the ENGAGED position, the

bell crank depresses the brake switch (S3) plunger and

the two unmarked terminals (normally opened) are

closed, providing a path for current to flow to the starter

solenoid (K1). With the small windings being

energized, the solenoid plunger closes the large main

terminals, supplying high battery current to the starter

motor (M1), engaging the bendix drive with the engine

flywheel, cranking the engine until the ignition circuit

fires (see Ignition Circuit Operation), igniting the fuel/air

mixture and starting the engine. Once the engine

starts, the operator releases the key and key switch

(S1) moves into RUN position. This breaks the current

flow to the starter solenoid (K1) plunger small windings,

opening the large main terminal and cutting off high

battery current to the starter motor.

The brake switch (S3) is also used to prevent the

engine from cranking if the drive train is engaged. This

is accomplished through the clutching linkage in the

gear models and the neutral return linkage in the hydro

models working in conjunction with the brake pedal

operation. With the brake pedal engaged, the brake

switch (S3) operation described above is repeated

1 ... 113 114 115 ... 314

Comments to this Manuals

No comments

John-deere stx38 User Manual Page 114

Comments to this Manuals

Related products and manuals for Special machinery John-deere stx38