Checking Cummins ISF3.8 Starting System Elements

To inspect the engine starting system components, a digital tester and connecting leads are required.

Checking the ignition switch operation

  1. Disconnect the lead connecting the ignition switch to the starter intermediate relay (marked “S” or “Start”) from the ignition switch terminal.
  2. Connect the positive probe of the digital tester to the ignition switch and the negative probe to the chassis or engine earth.
    Connecting the tester to the ignition switch
    Fig. 1. Connecting the tester to the ignition switch.
  3. Set the tester to DC voltage measurement with the ignition key in the “OFF” position. There must be no voltage at the ignition switch. If there is, replace the ignition switch.
    Checking the voltage in the “OFF” position
    Fig. 2. Checking the voltage in the “OFF” position.
  4. Turn the ignition key to the “Start” position. The tester must then show the rated voltage. If there is no voltage, continue the check.
    Checking the voltage in the “Start” position
    Fig. 3. Checking the voltage in the “Start” position.
  5. Turn the ignition key to the “OFF” position.
  6. Check the voltage in the ignition switch supply circuit by connecting the positive probe of the tester to the ignition switch terminal on which the lead going to terminal “B” of the starter relay is fitted.
    Checking the voltage in the ignition switch supply circuit
    Fig. 4. Checking the voltage in the ignition switch supply circuit.
  7. Turn the ignition key to the “Start” position.

If the tester shows the rated voltage at the ignition switch input terminal, the ignition switch must be replaced.

Checking the voltage at the ignition switch input terminal
Fig. 5. Checking the voltage at the ignition switch input terminal.

If the tester shows no voltage, the ignition switch is not the cause of the fault. The wiring, starter relay and battery must be checked.

Checking the starter intermediate relay

  1. Disconnect the terminal connecting the intermediate relay to the starter solenoid.
  2. Connect the probes of the digital tester to the ignition switch terminals.
  3. Set the digital tester to resistance measurement.
    Connecting the tester to the intermediate relay terminals
    Fig. 6. Connecting the tester to the intermediate relay terminals.
  4. Connect the tester probes to the two terminals of the intermediate relay.
  5. With the ignition key in the “OFF” position, the tester must show a resistance above 100 kΩ. If the resistance is lower, replace the intermediate relay.
  6. Turn the ignition key to the “Start” position. The tester must show a resistance below 10 Ω. If the resistance is higher, continue the check.
    Checking the intermediate relay resistance
    Fig. 7. Checking the intermediate relay resistance.
  7. Turn the ignition key to the “OFF” position.
  8. Set the digital tester to voltage measurement.
  9. Connect one tester probe to terminal “S” of the intermediate relay and the other to “earth”.
  10. Turn the ignition key to the “START” position.

If the tester shows no voltage, the starter intermediate relay is not the cause of the fault. If voltage is present, the intermediate relay must be replaced.

Checking the voltage at terminal “S” of the intermediate relay
Fig. 8. Checking the voltage at terminal “S” of the intermediate relay.
  1. Turn the ignition key to the “OFF” position.
    Disconnecting the tester probes
    Fig. 9. Disconnecting the tester probes.
  2. Disconnect the tester probes and connect the terminal joining the intermediate relay to the starter solenoid.

Checking the starter solenoid

  1. Connect the positive probe of the tester to the positive terminal of the starter solenoid and the negative probe to the chassis or engine “earth”.

The tester must show voltage (12 V or 24 V DC, depending on the system) when the ignition switch is in the “OFF” position, and the starter must operate.

If the tester shows no voltage, check whether the lead connecting the starter relay to the battery is broken. Make sure there are no poorly secured or corroded terminal connections.

Checking the voltage at the starter solenoid
Fig. 10. Checking the voltage at the starter solenoid.

If the tester shows voltage but the starter does not operate, check whether the lead connecting the starter relay to the ignition switch is broken, the fuses and the engine stop systems, and make sure there is no corrosion on the terminals.

If the lead connecting the starter relay to the ignition switch is not damaged and the starter still does not operate, do the following:

  • a) disconnect the lead connecting the solenoid to the starter from the relay terminal;
  • b) connect the positive probe of the tester to terminal “S” of the starter relay or of the starter intermediate relay, and the negative probe to the chassis or engine “earth”;
  • c) turn the ignition key to the “START” position.

If the tester shows voltage and the starter does not operate, the starter relay must be replaced.

Checking the voltage at terminal “S” of the starter relay
Fig. 11. Checking the voltage at terminal “S” of the starter relay.

If the tester shows no voltage, check the lead connecting terminal “S” of the starter relay or the ignition switch terminal to the starter intermediate relay for breaks and poorly secured or corroded connections. If there is no damage, replace the starter.

Checking the starter operation

  1. Clean the starter connectors of dirt and make sure they are not damaged.
  2. If the solenoid is heard operating but the engine does not start, turn the ignition key to the “OFF” position and try to turn the crankshaft using special tool No. 3824591.
    Checking crankshaft rotation
    Fig. 12. Checking crankshaft rotation.
  3. If the crankshaft turns, try to start the engine.
  4. If the starter turns the crankshaft, make sure the starter pinion and the flywheel ring gear are not damaged. Replace them if damaged.
    Checking the starter pinion and the flywheel ring gear
    Fig. 13. Checking the starter pinion and the flywheel ring gear.
  5. If the crankshaft does not turn, or if excessive force is required to turn it, make sure there is no internal damage or failure of the drive and auxiliary equipment.
    Checking the drive and auxiliary equipment
    Fig. 14. Checking the drive and auxiliary equipment.
  6. Measure the distance from the starter mounting flange to the front face of the flywheel ring gear.

Distance:

  • maximum: 52.32 mm;
  • minimum: 49.28 mm.
Measuring the distance from the starter mounting flange to the flywheel ring gear
Fig. 15. Measuring the distance from the starter mounting flange to the flywheel ring gear.
  1. Check the voltage at the starter terminals during operation.

If it drops by more than 2.4 V at 12 V and by more than 4.8 V at 24 V, make sure all connectors are clean and securely fastened. If the wiring is in good order and the voltage drop exceeds the norm, replace the starter.

Removal and installation of the starter

  1. Disconnect the lead from the battery negative terminal.
  2. Mark all the starter leads and disconnect them.
  3. Clean the surfaces around the starter with steam and dry them with compressed air.
    Cleaning the surfaces around the starter
    Fig. 16. Cleaning the surfaces around the starter.
  4. Unscrew the three bolts and remove the starter.
    Removal of the starter
    Fig. 17. Removal of the starter.

Installation of the starter

  1. Install the starter and tighten the three bolts. Tightening torque: 43 N·m.
    Installation of the starter
    Fig. 18. Installation of the starter.
  2. Connect the wiring to the starter. Tightening torques:
    • M5 — 4 N·m;
    • M10 — 21 N·m.
    Connecting the wiring to the starter
    Fig. 19. Connecting the wiring to the starter.
  3. Connect the lead to the battery negative terminal.

Starting and charging system diagrams

Starting and charging system diagram GAZ Valdai ISF3.8 Euro-4
Fig. 20. Starting and charging system diagram GAZ Valdai ISF3.8 Euro-4.
Starting and charging system diagram PAZ 4234-05 from 2011
Fig. 21. Starting and charging system diagram PAZ 4234-05 from 2011.
Starting and charging system diagram PAZ 4234-05 from 2013
Fig. 22. Starting and charging system diagram PAZ 4234-05 from 2013.
Starting and charging system diagram PAZ 3204/3204-12 from 2013
Fig. 23. Starting and charging system diagram PAZ 3204/3204-12 from 2013.

The above materials cover the inspection of the Cummins ISF3.8 engine starting system components: checking the ignition switch, the starter intermediate relay, the starter solenoid, the starter operation, as well as removal and installation of the starter; the starting and charging system diagrams for GAZ Valdai and PAZ vehicles are given at the end. The material is intended for diagnostics, fault-finding and repair of the starting system.