3003, 3013, 3014 and 3024 Engines for Caterpillar Built Machines Caterpillar

Illustration 1	g00754851
Typical example (1) Start disable relay (2) Neutral start switch (3) Key start switch (4) Fuse for neutral start switch (5) Fuse for fuel shutoff solenoid (6) Start relay (7) Fuel shutoff solenoid (8) Main power relay (9) Starting motor solenoid (10) Electric starting motor (11) Fuse for key start switch (12) Alternator (13) Disconnect switch (14) Battery (15) Main breaker (16) Starting aid relay (17) Glow plugs (18) Alternator circuit breaker

Table 1 shows the maximum acceptable loss of voltage in the circuits. The battery circuit supplies high current to the starting motor.

Voltage drops that are greater than the amounts in Table 1 are caused most often by the following conditions:

• Loose connections

• Corroded connections

• Faulty switch contacts

Procedures For Diagnosis Of The Electric Starting Motor

The procedures for diagnosing electric starting motor (10) are intended to help the service person determine if the electric starting motor needs to be replaced or repaired. The procedures are not intended to cover all possible problems and conditions. The procedures serve only as a guide.

General Information

The electrical starting system has the following components:

• Ignition switch

• Transmission Electronic Control Circuit

• Start relay (6)

• Starting motor solenoid (9)

• Electric starting motor (10)

• Starting aid switch

• Starting aid relay (16)

• Glow plugs (17)

• Fuel shutoff solenoid (7)

The coil of start relay (6) draws about 1 A. Start relay (6) allows current to flow to the starting motor solenoid (9) .

Starting motor solenoid (9) is a switch with a capacity of about 600 A. Starting motor solenoid (9) has two functions:

• The pinion gear is engaged with the ring gear of the flywheel.

• Electric starting motor (10) is rotated.

Starting motor solenoid (9) has two coils. The pull-in coil draws about 54.5 A. The pull-in coil is between contact "MTR" and contact "S". The hold-in coil draws about 10.5 A. The hold-in coil is between contact "G" and "S".

When start relay (6) closes, the pull-in coil and the hold-in coil receive power. Battery voltage is applied to the terminal "S" of starting motor solenoid (9) . Terminal "G" of the coil is permanently grounded to the ground post or the housing of the starting motor. Grounding for the terminal "MTR" of the pull-in coil is momentary. This ground takes place through the DC resistance of the starting motor.

When the magnetic force increases in both coils, the pinion gear moves toward the ring gear of the flywheel. Then, the solenoid contacts close in order to provide power to electric starting motor (10) . When the solenoid contacts close, the ground is temporarily removed from the pull-in coil. Battery voltage is supplied on both ends of the pull-in coil while electric starting motor (10) cranks. During this period, the pull-in coil is out of the circuit.

Cranking of the engine continues until current to starting motor solenoid (9) is stopped by releasing the ignition switch.

The power that is available during cranking varies according to the temperature and condition of the batteries. The following chart shows the voltages which are expected from a battery at the various temperature ranges.

Diagnosis Procedure

If electric starting motor (10) does not crank or cranks slow, perform the following procedure:

1. Measure the voltage of battery (14) at the battery posts with the multimeter when you are cranking the engine or attempting to crank the engine. Measure the voltage across the battery posts. Do not measure the voltage across the cable post clamps.

2. Battery voltage

   1. Go to Step 3 if the voltage is equal to the voltage that is given in Table 2 or if the voltage is greater than the voltage that is given in Table 2.

   2. The battery voltage is less than the voltage in Table 2.

      Refer to Special Instruction, SEHS7633 in order to test battery (14) .

      A low charge in a battery can be caused by several conditions.

      • Deterioration of the battery

      • A shorted starting motor

      • A faulty alternator

      • Loose drive belts

      • Current leakage in another part of the electrical system

3. Measure the current from the positive "+" battery terminal to starting motor solenoid (9) . Use the 225-8266 Ammeter Tool Gp . The maximum current that is allowed for no load conditions is given in the Specifications module, "Electric Starting Motor" topic.

   Note: If the following conditions exist, do not perform the test in Step 3 because electric starting motor (10) has a problem.

   • The voltage at the battery post is within 2 V of the lowest value in the applicable temperature range of Table 2.

   • The large starting motor cables get hot.

   The current and the voltages that are specified in the Specifications Module, "Electric Starting Motor" are measured at a temperature of 27 °C (80 °F). When the temperature is below 27 °C (80 °F), the voltage will be less than the values that are specified. Also, the current through electric starting motor (10) will be higher. If the current is too great, a problem exists in electric starting motor (10) . Repair the problem or replace electric starting motor (10) .

4. Measure the voltage from point "MTR" to the ground connection of electric starting motor (10) . Use the multimeter when you are cranking or attempting to crank the engine. Refer to Illustration 2.

5. Voltage between electric starting motor (10) from "MTR" to the ground connection of electric starting motor (10)

   1. The voltage is equal to the voltage that is given in Table 2 or the voltage is greater than the voltage that is given in Table 2.

      The battery and the electric starting motor cables to electric starting motor (10) are within specifications. Go to Step 8.

   2. The electric starting motor voltage is less than the voltage specified in Table 2.

      The voltage drop between battery (14) and electric starting motor (10) is too great. Go to Step 6.

6. Measure the voltage drops in the cranking circuits with the multimeter. Compare the results with the voltage drops which are allowed in Table 2.

7. Voltage drops in the cranking circuits

   1. The voltage is equal to the voltage that is given in Table 2 or the voltage is greater than the voltage that is given in Table 2. Go to Step 8 in order to check the engine.

   2. The voltage drops are greater than the voltage drops that are given in Table 2. The faulty component should be repaired or replaced.

8. Rotate the crankshaft by hand in order to ensure that the crankshaft is not stuck. Check the oil viscosity and any external loads that could affect the engine rotation.

   1. If the crankshaft is stuck or difficult to turn, repair the engine.

   2. If the engine is not difficult to turn, go to Step 9.

9. Attempt to crank electric starting motor (10) .

   1. Electric starting motor (10) cranks slowly.

      Remove electric starting motor (10) for repair or replacement.

   2. Electric starting motor (10) does not crank.

      Check for the blocked engagement of the pinion gear and flywheel ring gear.

      Note: Blocked engagement and open solenoid contacts will give the same electrical symptoms.

Start Relay Tests

If the engine does not start, perform these tests in order to find any fault of the start relay.

Illustration 2	g00470370
Schematic of the start relay and the starting aid relay (1) The position of the relay contacts is shown with an energized relay coil. (2) The position of the relay contacts is shown with a de-energized relay coil. (3) Connector pins on the relays

The start relay and the starting aid relay have a time delay for current overload.

The following test is with battery current.

Note: Some starting aid switches may be incorporated in the ignition switch.

1. Put the multimeter on the 200 V scale. Turn the ignition switch to the START position in order to check the start relay. Turn the starting aid switch to the ON position in order to check the starting aid relay for the glow plugs.

2. Put the multimeter leads on the "30" and "87a" terminals. The voltage across the leads should be zero V. The maximum permissible voltage drop is 250 mV.

   If the voltage drop is greater than 250 mV, the relay must be replaced.

The following test is with no battery current.

1. Put the multimeter on the 200 ohm scale. Put the multimeter leads on the "85" and "86" terminals. Two types of relays may be used. The resistance of the 9X-4207 Relay across the leads should measure 85 ± 5 ohms. The resistance of 115-1615 Relay across the leads is 7.2 ± 0.7 ohms.

   If the resistance is not correct, replace the relay.

2. If the resistance is correct, connect the leads of the 8T-0500 Continuity Test Light between the "30" and "87a" terminals. The test light should not turn on. If the test light turns on, the relay must be replaced. Then, move the probe of the test light from the "87a" terminal to the "87" terminal. The test light should turn on. If the test light does not turn on, the relay must be replaced.

   If the test light does not turn on for either test, the relay must be replaced. If the test light turns on for both tests, the relay must be replaced.

3. If the relay is not faulty, refer to the Testing and Adjusting, "Troubleshooting" topic for other tests.