1. Bring the engine to operating temperature, with all glow plugs operating correctly.
2. With the engine running, do the following things:
• Disconnect the wire from each glow plug.
• Separate the electrical connector for the generator (at the regulator).
• Install a magnetic probe tachometer.
• Adjust the engine speed to the point of rough idle (do not exceed 900 rpm).
• Allow the engine operation to stabilize for one minute.
3. As the engine continues to run, test each cylinder in the following steps:
• Adjust a high-impedence digital multimeter to the 200-ohm scale.
• Connect the meter negative lead to the injection pump bracket that supports the fast idle solenoid.
• Connect the meter positive lead to the electrical terminal of the glow plug of the cylinder to be tested.
• Observe the resistance reading of the glow plug.
• Test each cylinder in the firing order, noting the resistance on a chart (see example in Figure 7-76).
• Stop the engine.
• Allow the engine to rest for several minutes.
• Re-test each cylinder in the firing order, noting the resistance on a chart (see Figure 7-76).
4. Analyze the glow plug resistance readings:
• Readings during engine operation should be between 1.9 and 3.9 ohms, with a maximum variation of 0.4 ohm between cylinders.
– For cylinders with readings that vary more than 0.4 ohm when compared to the other cylinders, go to
step 5.
– For cylinders with readings below 1.6 ohms, perform a compression test to confirm a mechanical fault.
– For cylinders with varying readings and extremely erratic idle roughness, install a timing meter luminosity probe in each suspect cylinder (J 33300-1) to confirm erratic combustion.
• Readings with the engine at rest should be between 0.5 and 1.6 ohms.
– For cylinders with readings not within specifications, check meter operation and test lead connections.
5. Remove the nozzles from the cylinders with glow plug resistance readings that vary more than 0.4 ohm and do the following things:
• Test each nozzle for opening pressure, leakage, chatter and spray pattern.
– If a nozzle fails testing, substitute it with a new nozzle.
• Note the opening pressure of each nozzle on a chart (see Figure 7-77), including any new nozzle.
6. Analyze the opening pressure readings of the nozzles tested (see Figure 7-78):
• To increase the glow plug resistance reading of a cylinder, switch to a nozzle with a lower opening pressure.
• To decrease the glow plug resistance reading of a cylinder, switch to a nozzle with a higher opening
pressure.
7. Install the switched nozzles into the appropriate cylinders, following this procedure:
• Use a new compression gasket with each nozzle.
• Apply anti-seize compound on the cylinder head threads.
• Use a nozzle tightening torque of 60 to 80 N-m (44 to 55 Ib-ft).
« Tighten the injection line fitting nut to 27 to 39 N-m (19 to 29 Ib-ft) torque.
8. Connect the generator and glow plug wiring, start the engine and bring it to operating temperature.
9. Evaluate idle quality at the same speed as previously checked:
• If idle quality is acceptable, end the test.
• If idle quality is still not acceptable, see step 10.
10. With the engine running, repeat the glow plug resistance test, following steps 2 and 3.
11. Analyze the glow plug resistance readings (see Figure 7-79):
• If cylinders with previously varying readings are still out of specification, repeat the process of nozzle testing and substitution (steps 5, 6 and 7).
• If the readings for cylinders with varying readings do not change, replace the injection pump.
• If different cylinders now have varying readings, replace the injection pump.
12. Connect the generator and glow plug wiring, start the engine and bring it to operating temperature.
13. Evaluate idle quality at the same speed as previously checked:
• If idle quality is acceptable, end the test.
• If idle quality is still not acceptable, proceed with other testing.
