D7E Track-Type Tractor Power Train Systems Caterpillar

Starting System - Test

Usage:

D7E MDB

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Illustration 1	g03861123
Schematic for Engine Starting System

The ECM activates the intermediate start relay when the key switch is in the START position and the direction switch is in the NEUTRAL position. If a 168 code is present, the diagnostic code must be corrected before performing the following procedure "Check the key start switch". See Troubleshooting, "Diagnostic Code List".

After the Machine ECM detects the system voltage at the START input, the ECM will activate the intermediate starter relay. All of the following conditions need to be true for the software to energize the start relay:

Ignition Key in Start position
Starter Disconnect Switch is in the ON
The transmission in NEUTRAL position
Battery voltage is between 18 VDC and 32 VDC before the Start Relay is energized
Battery voltage is less than 32 VDC when the Start Relay is energized
Engine Speed is less than 400 RPM

The starter relays have system battery voltage on one side of the relay contacts. When the starter relays are energized by the intermediate start relay, system battery voltage is directed through the closed relay contacts. Next, the starter solenoids for the starter will energize. The starter solenoid contacts will close and +battery voltage will be applied to the starter in order to crank the engine for starting.

Perform the following procedure if the engine will not crank with the key start switch in the START position.

Note: Refer to the engine service manual for your machine if the engine cranks but the engine is not starting.

Verify that there are no active diagnostic codes for the intermediate starter relay. If a diagnostic code for the relay is active, troubleshoot the diagnostic code before attempting to start the engine.

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Table 1
Troubleshooting Test Steps	Values	Results
1. Verify That The Machine Conditions Are Correct A. Verify that the disconnect switch is in the ON position. B. Verify that the parking brake is engaged. C. Verify that the transmission is in NEUTRAL.	One or more of the listed machine conditions was not correct.	YES - One or more of the listed machine conditions was not correct. Repair: Ensure that all the listed machine conditions are correct. Then attempt to start the engine again. STOP. NO - All of the listed machine conditions are correct. The engine will not crank and there are not any diagnostic codes for the intermediate starter relay. Proceed to Test Step 2.
2. Check The Relays A. The key switch is in the OFF position. B. Obtain the aid of another technician. The other technician can place the key start switch in the START position. Observe the starter relay. The relay should create an audible "click" when the key start switch is first moved to the START position.	The relay is being energized.	OK - The relay is being energized. Proceed to Test Step 3. NOT OK - The relay is not being energized. Repair: There is a problem in the circuit for the starter relay. Refer to the Troubleshooting section of this manual. Find the problem in the relay circuit and repair the circuit.
3. Check The Condition Of The Batteries A. The key start switch is in the OFF position. B. At the starter relays, measure the battery voltage from the contact that is connected to the red cables 101-RD and a good frame ground. Verify that the correct voltage is present at the relay contact. If no voltage is present, check the circuit back to the batteries to determine the reason that there is not any system voltage at one side of the relay contacts. C. Verify that the battery connections are clean and tight. Perform Load test on the batteries. Use a 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8, and 12 V Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure".	The batteries pass the load test and the connections are in good condition.	OK - The batteries and the connections are OK. Proceed to Test Step 4. NOT OK - The batteries do not pass the load test or the connections are not in good condition Repair: Charge or replace the batteries. Clean the battery connections. Repair the battery connections. STOP.
4. Check The Voltage At the Starters A. Turn the key start switch to the OFF position. B. At the starters, measure the system voltage between the +battery contact (cable RD(Red)) and a good frame ground. C. At the starter, fasten ONE clamp-on multimeter probe to the starter solenoid contact and fasten the other clamp-on probe to a good frame ground. D. Observe the multimeter for a voltage measurement while the key start switch is in the START position for a few seconds.	System voltage is present at the + battery contacts (cable RD(Red)) on the starters. System voltage is present at contact on the starter with the key start switch in the START position.	OK - The system voltage is present at the starter solenoid contacts at the right time and system voltage is present at the contacts for the starter. Repair: The starters should be cranking the engine when the key start switch is in the START position. The starter has failed. Replace the starter. STOP. NOT OK - There is a problem with the system voltage at the starter or at the solenoid for the starter. Repair: Investigate the circuit that is not providing the correct voltage at the starter or the solenoid for the starter. Repair the system voltage circuit. Verify the presence of voltage at the contact of the starter relay if the voltage is not present at the solenoid for the starter with the key start switch in the START position. Check the operation of the relay. Check the wire from the starter relay to the solenoid of the starter. STOP.