STARTING MOTOR GROUP 4N8118 - Caterpillar

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System Schematic For Starting Motor Relay (SMR)
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System Schematic For Electronic Governor (EG) Relay
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System Schematic For Air Shutdown Relay (ASR)To find the cause of an overcrank shutdown, perform this procedure.
Preliminary Step. Initial Check. Before proceeding with the troubleshooting procedures, do the following preliminary checks.
Check for active diagnostic codes (with the exception of the CID 566 FMI 7) and other flashing indicators on the GSC. If the fault is present, then correct the fault first. Go to the appropriate procedure for that fault.
Check the fuel level and quality. Refer to the Engine Service Manual.
Check for a plugged fuel filter. Refer to the Engine Service Manual.
Check for a plugged air filter. Refer to the Engine Service Manual.
Check the air shutoff solenoid (if equipped) for activation. The solenoid must be deactivated in order for the engine to start. See Testing And Adjusting, "Troubleshooting Diagnostic Codes".
Check fuse "F2" and "F4" on the relay module. If either fuse is blown, proceed to 10.
Check the engine starting system and the fuel system. (To check the fuel control solenoid, see Testing And Adjusting, "Troubleshooting Diagnostic Codes".) If there is a fault, refer to the Engine Service Manual. If there is no engine fault or fuel system fault, proceed to 2.
Check setpoints.This step checks setpoints P17 (total cycle crank time) and P18 (cycle crank time).
View and note setpoints P17 and P18. See Systems Operation, "Engine/Generator Setpoint Viewing OP2".
Compare the setpoints viewed with the specified setpoints of the particular generator set. The factory default values are 90 seconds for P17 and 10 seconds for P18.Expected Result: The viewed setpoint value and the specified setpoint value should agree.Results:
OK - Proceed to next step.
Not OK - The setpoints do not agree. Reprogram setpoints P17 and P18. See Systems Operation, "Engine/Generator Programming OP5". STOP.
Check the battery voltage.
Make sure that the engine is off. Measure the system voltage at the batteries.Expected Result:For 24 volt systems, the voltage should be from 24.8 to 29.5 DCV.For 32 volt systems, the voltage should be from 33.1 to 39.3 DCV.Results:
OK - Proceed to next step.
NOT OK - Further checking of the battery system is necessary. See Testing And Adjusting, "Troubleshooting Diagnostic Codes". STOP.
Check the engine starting function. Steps 4 through 9 require voltage measurements to be made during simulated engine cranking. The starting motor is disabled.Note: The GSC is attempting to crank whenever the K4 indicator is ON (on the lower display). Be aware of the 10 second crank cycle that is factory set. Ensure that the K4 indicator is ON while you are making the following measurements. Have a helper observe the GSC display, if necessary. More than one start may be required to complete this test.
Disconnect the B+ wire on the pinion solenoid of the starting motor. The B+ wire remains disconnected for all of the remaining steps of this procedure.
Prepare to measure the DC voltage from the disconnected "B+" pinion solenoid wire to "B-" (ground).
Turn the ECS to the OFF/RESET position and then turn the ECS to the START position.
Measure