Caterpillar PRELUB® Diagnostics{1469} Caterpillar

Commercial and Truck Engines: All

Machine Engines: All

Earthmoving Compactor:

826G (S/N: 7LN1-UP)

836 (S/N: 7FR1-UP)

Wheel Loader:

980G (S/N: 2KR1-UP)

988F Series II (S/N: 2ZR1-UP)

990 Series II (S/N: 4FR1-UP)

Wheel Tractor:

834B (S/N: 7BR1-UP)

Introduction

This Special Instruction applies to all Caterpillar machines with engines that are equipped with the PRELUB^® Engine Prelubrication System.

The Caterpillar PRELUB System uses the starter motor to run an oil pump. This oil pump primes the engine oil system before starting the engine. This information applies to machines using the Caterpillar PRELUB system that is equipped with the 139-1585 140-3108 Timer Assemblies . There are other prelubrication systems that are installed on machines that are made by Caterpillar. This Special Instruction is not applicable to these other systems.

Important Safety Information

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs.

A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools in order to perform these functions properly.

Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard.

Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. If a tool, a procedure, a work method, or operating technique that is not specifically recommended by Caterpillar is used, ensure that it is safe for you and for other people to use.

Ensure that the product will not be damaged or the product will be made unsafe by the operation, lubrication, maintenance, or the repair procedures that are used.

Normal Operation

1. Turn the key switch to the CRANK position and hold the key switch in the CRANK position.

2. The starter motor runs in PRELUB Mode. The motor spins but the flywheel is not engaged. The starter motor runs for 3 to 45 seconds until oil pressure reaches between 27 kPa (4 psi) and 48 kPa (7 psi). The oil pressure is measured at the oil pressure switch.

3. The key switch is still held in the CRANK position. The starter is delayed for 3 seconds and the spinning stops.

4. The starter then engages the flywheel and the engine is cranked normally.

Basic Operation Of The PRELUB Timer

Illustration 1	g00557737
Basic PRELUB electrical schematic

Illustration 2	g00557729
Circuitry of the timer (1) Relay control. (2) Three-second delay control.

Power from the keyswitch is supplied to Contact 1 of the timer when the keyswitch is in the CRANK and RUN positions. Contact 1 supplies power to the electronic circuits that are inside the timer. Contact 2 connects through the wiring harness to the starter solenoids ground terminal. When the PRELUB oil pressure switch detects pressure less than 27 kPa (4 psi), Contact 4 is connected to ground. Power from Contact 3 (CRANK) then passes through the normally closed internal relay. The PRELUB magnetic switch is then energized. When the magnetic switch closes, current flows to the motor terminal on the starter solenoid. The starter motor is allowed to run without engaging the starter drive.

When the starter motor runs, the PRELUB pump will pressurize the oil system. The PRELUB pump draws oil from the engine oil pan. The oil is then pumped into the engine oil system through the oil hoses of the PRELUB system. The oil pressure is measured at the PRELUB oil pressure switch. When the oil pressure exceeds 27 kPa (4 psi) to 48 kPa (7 psi), the timer turns off the magnetic switch of the PRELUB system. The starter motor will stop turning. The timer will wait for 3 seconds. An internal relay in the timer will then allow power from the key switch (Contact 3) to pass through Contact 5 on the timer. The starter will now crank normally.

Note: After PRELUB has been activated, PRELUB will not activate again until the key switch has been in the OFF position for a minimum of 2 minutes.

The timer is located on the electric circuit between the key switch and the transmission ECM. The timer is also located on the electric circuit between the key switch and any other control that prevents cranking.

Initial Troubleshooting Procedure

Note: During PRELUB Mode, the starter motor runs but the drive is disengaged from the engine. The engine will not crank in this mode but the starter motor will spin. The battery disconnect switch must be ON for all testing unless otherwise stated. Batteries must be fully charged.

The key must be in the OFF position for more than 2 minutes between tests that involve the PRELUB Mode.

If you are testing alone, use the "Peak Hold" feature on your DMM in order to record the voltage readings from the tests below. Turn on the DMM. Turn on the DMM's "Peak Hold" or "Record" feature. Refer to the DMM instructions when performing the following tests. The "Peak Hold" mode on the DMM must be reset before each step. All connections must be made prior to entering "Peak Hold" mode.

Note: This Special Instruction can be used for the 4Q-5450 Timer Switch Assembly if the following changes are noted:

• The 4Q-5450 Timer Switch Assembly does not have a "113" circuit (Contact 1). A yellow wire is in Contact 1 of the connector but this wire is not used.

• The negative wire to the PRELUB magnetic switch is green. The PRELUB magnetic switch is mounted to the timer on this type.

• Contact 5 on both systems goes to the starting circuit. The wire color on the 4Q-5450 Timer Switch Assembly (Contact 5) is white and black rather than yellow on the other timers.

• The delay of 2 minutes (key OFF) to inhibit PRELUB Mode does not apply to the 4Q-5450 Timer Switch Assembly .

Test 1

1. Check PRELUB Magnetic Switch.

   1. Connect a DMM to the two small terminals on the PRELUB magnetic switch. Connect the negative lead of the DMM to the negative terminal on the PRELUB magnetic switch. Connect the positive lead of the DMM to the positive terminal on the PRELUB magnetic switch. On newer timers, the red/white wire is the negative side of the coil on the PRELUB magnetic switch. On all timers, the lead from the negative coil on the PRELUB magnetic switch comes out of the timer. The wire is next to the black wire (Contact 4).

   2. Turn on the DMM. Set the DMM to "DC volts". Hold the key in the CRANK position for at least 5 seconds.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read 10V for 12V systems.

      Results:

      • Yes - The PRELUB timer is attempting to enter PRELUB Mode. The oil pressure switch is properly grounded and power is available to the timer. Go to Step 4.

      • No - The PRELUB magnetic switch is not being energized. Go to Step 2.

2. Check Ground Circuit.

   1. Insert a multimeter probe into the back of Contact 2 (ground). Insert the probe on the side of the 6-pin connector that goes to the timer.

   2. Connect the multimeter probe to the positive terminal on the DMM. Connect the negative lead to a good ground.

   3. Turn on the DMM and set the DMM to "DC Volts". Hold the key in the CRANK position for at least 5 seconds.

      Expected Result: The DMM reads at least 1V while the key is in the CRANK position. The DMM should read .5V for 12V systems.

      Results:

      • Yes - Ground circuit (200) has high resistance. Check the following items for damage, corrosion, or poor connections: the ground wire from the PRELUB 6-pin connector (Contact 2), the ground terminal for the starter solenoid, the engine to frame grounds and the negative battery post to engine ground. Make sure that the main disconnect switch is turned ON. Make sure that the main disconnect switch is working properly by checking continuity. Repair the problems with the circuit and retest the system.

      • No - Go to Step 3

3. Check For Power From The Keyswitch.

   1. Insert a multimeter probe into the back of Contact 3 (CRANK). Insert the probe on the side of the 6-pin connector that goes to the timer.

   2. Connect the multimeter probe to the positive terminal on the DMM. Connect the negative lead to ground.

   3. Turn on the DMM. Set the DMM to "DC Volts". Hold the key in the CRANK position for at least 5 seconds.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read at least 10V for 12V systems.

      Results:

      • Yes - Go to Step 4.

      • No - There is no power from the key switch ON Circuit 337 of the machine wiring. Check the wiring from the key switch to the PRELUB 6-pin connector. Check for wires that are loose, corroded, or damaged. Check the key switch for proper operation. Check related fuses and breakers. Repair the problems with the circuit. Retest the system.

4. Check for Power to the PRELUB Magnetic Switch.

   1. Connect the negative lead of the DMM to ground.

   2. Set the DMM to "DC Volts". Touch the DMMs positive lead to one of the large terminals on the PRELUB magnetic switch.

   3. Read the DMM. Then touch the DMMs positive lead to the remaining large terminal on the PRELUB magnetic switch.

      Expected Result: One of the terminals has system voltage.

      Results:

      • Yes - Note the remaining large terminal as the battery terminal on the PRELUB magnetic switch. Continue to Step 6.

      • No - There is no power to the PRELUB magnetic switch. Go to Step 5.

5. Check Harness.

   1. Connect the negative lead of the DMM to ground. Touch the positive lead of the DMM to the starter solenoids B+ terminal.

   2. Turn on the DMM. Set the DMM to "DC Volts". Check for system voltage.

      Expected Result: The terminal has system voltage.

      Results:

      • Yes - There is an open circuit in the PRELUB wiring between the battery terminal of the starter solenoid and the PRELUB magnetic switch (Circuit 101). Repair the wiring from the starter solenoid to the PRELUB magnetic switch. Retest the system.

      • No - Repair the open circuit in the battery to starter wiring. The open circuit could be caused by one of the following problems: loose connections, broken wires, corroded wires and faulty disconnect switch. Ensure that the main disconnect switch is working properly. Ensure that the wiring from the battery to the frame and engine grounds is good. See Starting System Diagnostic Procedures to continue.

6. Check PRELUB Magnetic Switch.

   1. Connect the positive lead of the DMM to the motor terminal on the PRELUB magnetic switch. The motor terminal is the large terminal opposite the battery terminal that was found in Step 4.

   2. Turn on the DMM. Set the DMM to "DC Volts".

   3. Hold the key in the CRANK position for 5 seconds.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read at least 10V for 12V systems.

      Results:

      • Yes - There is an open circuit in the large wire from the PRELUB magnetic switch to the starter motor terminal (Circuit 301). Go to Step 7.

      • No - Replace the PRELUB magnetic switch and retest the system.

7. Check Harness.

   1. Connect the positive lead of the DMM to the motor terminal on the starter solenoid. The motor terminal is the large terminal toward the motor. Connect the ground lead of the DMM to ground.

   2. Turn on the DMM. Set the DMM to "DC Volts".

   3. Hold the key in the CRANK position for 5 seconds.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read at least 10V for 12V systems.

      Results:

      • Yes - If the starter motor does not run, replace the starter motor and retest the system.

      • No - Repair or replace the PRELUB wire (301) from the PRELUB magnetic switch to the motor terminal on the starter solenoid. Retest the system.

Test 2

1. Check Harness.

   1. Insert a multimeter probe into the back of Contact 4 (oil pressure switch). Insert the probe on the side of the 6-pin connector that goes to the timer.

   2. Connect the multimeter probe to the positive terminal on the DMM. Connect the negative lead to ground.

   3. Turn on the DMM. Set the DMM to "DC Volts".

   4. Hold the key in the CRANK position for at least 5 seconds.

      Expected Result: The DMM reads at least 1V while the key is in the CRANK position. The DMM should read at least .5V for 12V systems.

      Results:

      • Yes - The oil pressure switch circuit is not grounded with the engine OFF. This condition may be caused by one of the following problems: an open circuit in the wiring, poor wiring connections and a faulty PRELUB oil pressure switch. Go to Step 2.

      • No - Replace the timer and retest the system.

2. Check Oil Pressure Switch.

   Leave the DMM connected as in Step 1 above.

   1. Make sure that all of the electrical connections of the PRELUB system are properly connected.

   2. Disconnect the oil pressure switch. Connect a jumper wire between the two terminals in the connector for the oil pressure switch.

   3. Turn on the DMM. Set the DMM to "DC Volts".

   4. Hold the key in the CRANK position for at least 5 seconds.

      Note: If the starter motor now runs in PRELUB Mode, replace the oil pressure switch.

      Expected Result: The DMM reads at least 1V while the key is in the CRANK position. The DMM should read at least .5V for 12V systems.

      Results:

      • Yes - The oil pressure switch wiring has an open circuit. Go to Step 3.

      • No - Make sure the terminals in the PRELUB oil pressure switch connector are clean and in good condition. Replace the PRELUB oil pressure switch and retest the system.

3. Check Harness. Leave the DMM connected from the previous step.

   1. Connect a jumper wire from the pink wire (circuit A447) at the PRELUB oil pressure switch connector to ground.

   2. Turn on the DMM. Set the DMM to "DC Volts".

   3. Hold the key in the CRANK position for at least 5 seconds.

      Expected Result: The DMM reads at least 2V while the key is in the CRANK position. The DMM should read at least .5V for 12V systems.

      Results:

      • Yes - Repair the open circuit wire (A447) between the PRELUB timer and the PRELUB oil pressure switch connector. Check the connections for corrosion or damaged pins. Repair the problems with the circuit and retest the system.

      • No - An open circuit exists between the PRELUB oil pressure switch connector and the starter solenoid ground (Circuit 200). Repair the problems with the circuit and retest the system.

Test 3

1. Check for PRELUB Oil Pressure Switch Operation.

   1. Disconnect the connector for the PRELUB oil pressure switch.

   2. Turn the key to the CRANK position. Hold the key in the CRANK position for more than 10 seconds.

      Expected Result: The starter cranks the engine after a three-second delay.

      Results:

      • Yes - The PRELUB oil pressure switch is not working properly or the PRELUB oil pressure switch never exceeds between 27 kPa (4 psi) and 48 kPa (7 psi). Go to Step 2.

      • No - The wire from the PRELUB timer connector is shorted to ground or the timer is faulty. Go to Step 7.

2. Check Oil Pressure.

   1. Remove the oil pressure switch from the engine.

   2. Connect an oil pressure gauge to the engines oil pressure switch port.

   3. Connect a jumper wire between the terminals in the connector of the PRELUB oil pressure switch.

   4. Turn the key to the CRANK position and observe the oil pressure. Hold the key in the CRANK position until one of the following events occurs: the oil pressure is 48 kPa (7 psi), or 45 seconds pass.

      Expected Result: The oil pressure exceeds 48 kPa (7 psi).

      Results:

      • Yes - Replace the PRELUB oil pressure switch and retest the system.

      • No - Go to Step 3.

3. Check Oil In The Engine.

   Check that the engine oil pan is filled to the proper level with clean oil.

   Expected Result: The oil is good.

   Results:

   • Yes - Go to Step 4.

   • No - Fill to proper level with good oil or change oil as needed. Retest the system. If the oil is contaminated, determine the root cause in order to prevent a recurrence.

4. Check PRELUB Pump Output.

   1. Remove the pressure hose (outlet) from the pump.

   2. Connect a hose from the pressure port to a suitable container. Ensure that the hose remains in the container.

   3. Turn the key to the CRANK position until one of the following events occurs: the oil pressure is 48 kPa (7 psi), or 45 seconds pass.

      Expected Result: Oil flows from the hose.

      Results:

      • Yes - Go to Step 6.

      • No - Go to Step 5.

5. Check Oil Suction Tube.

   Check the suction hose for air leaks and restrictions. Make sure that the end of the suction tube is immersed in oil.

   Expected Result: There are air leaks or restrictions.

   Results:

   • Yes - Repair leaks or restrictions and retest the system.

   • No - Replace the PRELUB starter motor.

6. Check Pressure Hose and Check Valve.

   Check that the PRELUB oil check valve is properly installed. The arrow must be pointing in the direction of oil flow. Check the pressure hose for restrictions.

   Expected Result: The check valve was installed properly and the hoses are free of restrictions.

   Results:

   • Yes - The oil system in the engine has a large internal leak, blocked oil passages, or excessive engine bearing wear. Repair the system and retest the system.

   • No - Install the check valve properly and/or repair pressure hose restrictions as needed. Retest the system.

7. Check Harness To PRELUB Oil Pressure Switch.

   1. Remove Pin 4 (black wire) from the PRELUB 6-pin connector.

   2. Reconnect the connector and hold the key in the CRANK position for at least 10 seconds. If the engine cranks after a delay, release the key.

      Expected Result: The starter has a delay. After the delay, the starter cranks the engine.

      Results:

      • Yes - Repair the short to ground in the wire (circuit A447) from Contact 4 to the PRELUB oil pressure switch and retest the system. Remember to reinstall Pin 4 in the 6-pin connector.

      • No - Replace the PRELUB timer and retest the system. Remember to reinstall Pin 4 in the 6-pin connector.

Test 4

Note: Tapping on the PRELUB magnetic switch may temporarily break the weld that is causing the contact disk to stick in the PRELUB magnetic switch. Normal operation would be temporarily restored, then replace the PRELUB magnetic switch. Caterpillar does not recommend this action due to the possibility of breaking the component. Similarly, tapping on the starter solenoid may temporarily break the weld that is causing the contact disk to stick inside the starter solenoid. Normal operation would be temporarily restored, then replace the starter solenoid. Caterpillar does not recommend this action due to the possibility of breaking the component.

1. Check Harness.

   Make sure that the batteries are fully charged and make sure that the batteries are in good condition. Low cranking voltage may contribute to welding of the contact disk.

   1. Turn OFF the main disconnect switch.

   2. Disconnect one of the large wires from the PRELUB magnetic switch.

   3. Turn ON the disconnect switch.

      Expected Result: The starter motor still runs.

      Results:

      • Yes - Turn OFF the disconnect switch. The PRELUB magnetic switch or the PRELUB wiring is shorted. Go to Step 2.

      • No - Replace the PRELUB magnetic switch and retest the system.

2. Check Harness.

   1. Disconnect the PRELUB wire from the motor terminal on the starter solenoid.

   2. Turn ON the disconnect switch.

      Expected Result: The starter motor still runs.

      Results:

      • Yes - The contact disk inside the starter solenoid is stuck. Replace the starter solenoid and retest the system. If the starter motor shows signs of damage, also replace the starter motor.

      • No - The wiring from the PRELUB magnetic switch and the starter motor is shorted. Repair the problems with the circuit and retest the system.

Test 5

1. Check for Excessive Starter Current.

   1. Connect a current probe (DC) around either of the large wires that are connected to the PRELUB magnetic switch. Use a 155-5176 Current Probe .

   2. Turn the key to the CRANK position. Observe the current after the starter motor has run for more than 2 seconds in PRELUB Mode.

      Note: Do not use "Peak Hold" or "Record Mode" on the DMM for this test.

      Expected Result: The DMM reads at least 300A while the key is in the CRANK position. The DMM should read at least 400A for 12V systems.

      Results:

      • Yes - The starter current is excessive. Go to Step 2.

      • No - Service batteries and charge batteries as needed. Check PRELUB wiring connections from the starter solenoid to the PRELUB magnetic switch for looseness, corrosion, or hot spots. Make sure that the ground connections are good. Repair the problems with the circuit and retest the system.

2. Check for Oil Leakage.

   Check for oil inside the starter motor.

   Expected Result: Oil is present inside the starter motor.

   Results:

   • Yes - Oil is present could be accompanied by a PRELUB pump lid gasket failure, which is an indication of a PRELUB Check Valve failure, or excessive restrictions in the Pressure hose of the PRELUB system. Go to Step 3.

   • No - Replace the starter motor and retest the system.

3. Pinpoint Oil Leak.

   The oil could be entering from the starter nose housing or the oil could be entering from the PRELUB pump. Remove the starter and inspect the nose housing.

   Results:

   • Oil appears to be coming from the nose housing. Replace the starter and retest the system.

   • Oil appears to be coming from the PRELUB pump. Replace the starter. Replace the PRELUB check valve. Repair any restrictions in the pressure hose. Retest the system.

Test 6

Test 6 can be made much quicker and easier by making a PRELUB bypass connector. To make the PRELUB bypass connector, perform the following procedure.

Procedure to Build a PRELUB Bypass Connector

1. Using the proper crimp tool, install 9W-0852 Connector Pins on each end of the 14 AWG wire.

2. Insert one end of the 14 AWG wire (with 9W-0852 Connector Pin installed) into Location 3 of the 102-8805 Receptacle Kit . Insert the remaining end of the 14 AWG wire (with 9W-0852 Connector Pin installed) into Location 5 of the 102-8805 Receptacle Kit .

3. The PRELUB bypass connector can now be plugged into the PRELUB wiring harness in place of the timer. This will restore normal operation of the starter with no PRELUB function. If the starter now works normally (less the PRELUB mode and delay), replace the PRELUB timer. If the starter still chatters or does not engage, begin with Step 2 below.

The batteries must be fully charged and the battery cables must be clean and tight before continuing.

1. Test For PRELUB Timer Fault.

   Note: The PRELUB Mode and delay will not function during this test.

   1. Disconnect the PRELUB timer.

   2. Connect a jumper wire from Contact 3 to Contact 5. Be careful too not short to any other wires in the connector. Do not damage the PRELUB harness connector.

      Expected Result: The engine cranks normally.

      Results:

      • Yes - Replace the PRELUB timer. Retest the system.

      • No - The wiring, starter relay, or starter solenoid is at fault. Go to Step 2.

2. Check Current from Keyswitch.

   Leave the jumper wire or bypass connector (from above) in place for this test.

   1. Insert a connector probe into Contact 5 of the PRELUB harness connector (on the harness side).

   2. Turn on the DMM. Set the DMM to "DC Volts".

   3. Hold the key in the CRANK position for 3 seconds.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read at least 10V for 12V systems.

      Results:

      • Yes - The key switch and wiring to the PRELUB timer is OK. Go to Step 3.

      • No - There is insufficient current from the key switch. The key switch, related wiring, or connections need repair. Repair the problems with the circuit and retest the system.

3. Check Harness.

   Leave the jumper wire or bypass connector (from above) in place for this test.

   1. Connect the positive lead from the DMM to the positive terminal on the starter relay coil.

   2. Connect the negative lead to the ground terminal on the starter solenoid.

   3. Hold the key in the CRANK position for 3 seconds.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read at least 10V for 12V systems.

      Results:

      • Yes - The PRELUB system and wiring are good. The starter relay, starter solenoid, or related wiring/connections are at fault. Pinpoint the fault and repair as needed.

      • No - The circuit from the PRELUB timer has excessive voltage drop. The circuit (307) goes through the following components: Contact 5 in the PRELUB connector, the transmission control, any other starter lockout system and the starter relay coil. Check all related connections for corrosion and proper connection. Check the related wiring for damage. Verify the integrity of all starter lockout devices such as the transmission control. Repair the problems with the circuit and retest the system.

Test 7

1. Check Key ON Circuit from Keyswitch.

   1. Connect the positive DMM probe to the backside of Contact 1 (Circuit 113) in the PRELUB timer connector.

   2. Connect the negative DMM probe to ground.

   3. Turn on the DMM. Set the DM to "DC Volts".

   4. Turn the key to the RUN position.

      Expected Result: The DMM reads at least 20V while the key is in the CRANK position. The DMM should read at least 10V for 12V systems.

      Results:

      • Yes - Replace the PRELUB timer and retest the system.

      • No - The key ON circuit (113) from the key switch to the PRELUB timer has a fault (high resistance or open circuit). Repair the problems with the circuit and retest the system.