LOCKNUT 4D6432 - Caterpillar

The control board controls the activation of the fuel system and the engagement of the starting motor for the 3412 PEEC engines and the 3412/3500 MUI engines. The engine ECM controls the activation of the 3500 EUI engines.3412/3500 MUI Engine Control
The remote start switch is a normally open switch. This customer-provided switch is located in the customer connection box.
The remote start switch is closed between remote start terminal 57 and remote start terminal 30.
The start signal is passed to connector contact number 24 of the control board.
The control board will then attempt to activate the fuel control solenoid and the starting motor.3412 PEEC And 3412/3500 MUI Fuel System Activation
When the control board receives a start signal, the control board sends a fuel-on signal from connector contact number 9 to the coils of the fuel control relay.
The signal passes through the normally closed contacts of the emergency stop push button ("ESPB"). The signal then passes through the optional enclosure's emergency stop contacts.
When the FCR coils receive the fuel-on signal, the following contacts close: normally open connector contact number 30 (FCR1) and normally open connector contact number 87 (FCR2). These contacts close in order to energize the fuel control solenoid. Fuel is now provided to the engine during starting.
When the remote start signal is not present at connector contact 24 of the control board, the control board removes the fuel-on signal from the coils of FCR1 and FCR2. This de-energizes the fuel control solenoid and the engine shuts down.3412 PEEC And 3412/3500 MUI Starting Motor Control
When a start signal is received, the control board sends a start-motor signal from connector contact number 13 to the starting motor's magnetic switch ("SMMS1"). This signal is sent through the normally closed contacts of the emergency stop push button ("ESPB") and through the optional enclosure's emergency stop contacts.
The closed contacts of SMMS1 will energize the pinion solenoid and the starting motor will operate.
The starting motor will operate according to the cycle crank function. See Systems Operation, "Cycle Crank" for more information.
After the engine speed reaches crank terminate speed, the control board turns off the start motor signal. SMMS1 is then de-energized. Also when crank terminate speed is reached, the control board energizes the internal fault protection timer ("FPT"). See Systems Operation, "Fault Management" for additional information about faults.
The control board stops the cranking for two possible reasons.
During the normal cycle cranking, the magnetic pickup provides the signal that is used in order to determine the speed of the engine. During the normal cycle cranking, the engine speed reaches 25% of the crank termination speed.
When a generator running signal ("B+") is present, the control board stops the cranking. This is meant as a backup to the normal crank termination speed. The generator running signal is provided by the arming relay contact and the generator running signal is triggered by the generator output voltage.Note: Pressing the emergency stop push button (ESPB) opens the circuit to the starting motor magnetic switch which stops engine cranking.
Table 1
Crank Termination