26404 Mercury CLAMP

Illustration 1 g01166547
Typical circuit with engine control
Test Step 1. Inspect Electrical Connectors and Wiring
Place the engine control in the OFF/RESET mode.
Turn the battery disconnect switch to the OFF position.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the ECM connector (allen head screw) for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the customer connector (allen head screw) for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The connectors and wiring are OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring are not OK.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOPTest Step 2. Check the Supply Voltage to the Speed Control
Turn the battery disconnect switch to the ON position.
Place the engine control in the STOP mode.
Connect one probe of a voltmeter to the +Battery terminal of the speed control. Connect one probe of the voltmeter to the −Battery terminal of the speed control. Expected Result:The voltage is 24 3 VDC.Results:
OK - The voltage is 24 3 VDC. The voltage supply to the speed control is correct. Proceed to Test Step 3.
Not OK - The voltage is not 24 3 VDC.Repair: Check wire 998-BK(Black) for continuity to the ECM connector P1-66. Check the wires for continuity to the "relay breaker". Check the breakers.STOPTest Step 3. Determine the Component that has Failed
Determine if the problem is with the input for the throttle or the droop.
Place the engine control in the STOP mode. Turn the battery disconnect switch to the ON position.
Observe the position of the throttle on the Caterpillar Electronic Technician (ET) as you turn the speed adjust potentiometer.
Observe the droop on Cat ET as you turn the droop adjust potentiometer. Expected Result:The throttle position on Cat ET varies with the turning of the speed adjust potentiometer. The droop on Cat ET varies with the turning of the droop adjust potentiometer.Results:
RATED SPEED - The throttle position on Cat ET does not vary with the turning of the speed adjust potentiometer. Proceed to Test Step 4.
DROOP SPEED - The droop on Cat ET does not vary with the turning of the droop adjust potentiometer. Proceed to Test Step 5.
Unsure - The problem is not apparent. Proceed to Test Step 4.Test Step 4. Check the Throttle Position
Place the engine control in the STOP mode. Turn the battery disconnect switch to the ON position.
Observe the position of the throttle on Cat ET.
Turn the speed adjust potentiometer to the lowest setting.
60 Hz equals 1369 rpm.
50 Hz equals 1141 rpm.
Start at the low idle position. Slowly turn the speed adjust potentiometer in the other direction. Monitor the position of the throttle on Cat ET. Expected Result:The throttle position on Cat ET reads 0 percent at the lowest setting and 0 to 100 percent as the speed adjust potentiometer is adjusted.Results:
OK - The speed control is operating correctly.Repair: The problem may be intermittent. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".STOP
Not OK - The throttle position on Cat ET does not vary as the speed adjust potentiometer is adjusted. Proceed to Test Step 6.Test Step 5. Check the Droop Signal on Cat ET
Place the engine control in the STOP mode. Turn the battery disconnect switch to the ON position.
Observe the droop on Cat ET.
Turn the droop adjust potentiometer in a counterclockwise direction.
Slowly turn the droop adjust potentiometer in a clockwise direction. Monitor the droop on Cat ET. Note: Do not overturn the droop adjust potentiometer in the clockwise direction. The signal will become erratic.Expected Result:The droop on Cat ET reads 0 percent at the lowest setting and 0 to 10 percent as the droop adjust potentiometer is adjusted.Results:
OK - The droop is operating correctly.Repair: The problem may be intermittent. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".STOP
Not OK - The droop on Cat ET does not vary as the droop adjust potentiometer is adjusted. Proceed to Test Step 7.Test Step 6. Check the Speed Control
Remove the wire from the S terminal at the speed control.
Set the multimeter to "VDC". Press the "Hz" button twice in order to display the "%" symbol.
Place one probe of the multimeter on the S terminal of the speed control. Place the other probe on the −Battery terminal of the speed control.
Monitor the output of the percent duty cycle from the speed control on the multimeter. Turn the speed adjust