Cummins NT Diesel Engines Maintenance Checks

by Starlight Generator dieselgeneratortech

In this article, we mainly talk about how to adjust injector and valve of Cummins diesel engines in a correct way. In addition, the engine temperature of the generator set is also required when adjusting the injector and valve.

Note: At each “C” Maintenance Check, first perform all “A”, and “B” Checks in addition to those following:

Adjust Injectors and Valves

It is essential that the injectors and valves be in correct adjustment at all times for the engine to operate properly. One controls engine breathing; the other controls fuel delivery to the cylinders.

Final operating adjustments must be made using correct values as stated.

Cautions: Be sure the injector and valve set markings, wherever located, are in proper alignment with the indicator mark.

Engine Temperatures

The following temperature conditions provide the necessary stabilization of engine components to allow for an accurate valve and injector adjustment.

Cummins Engine Company, Inc, recommends that valve and injector plunger adjustments be made when the engine is cold. The engine must be at any stabilized temperature of 140°F [60°C] or below.

A second setting or resetting after the engine is warm is not recommended.

Non Top-Set Injector and Valve Adjustment (Dial Indicator Method)

Before adjusting the injectors, torque the cylindrical injector, hold-down capscrews in alternate steps to 10 to 12 ft-lbs [14 to 16 N*m]. With flange injectors torque the hold-down capscrews in alternate steps to 12 to 14 ft-lbs [16 to 18 N*m]. Tighten the fuel inlet and drain connections to 20 to 25 ft-lbs [27 to 34 N*m] in the flange injectors.

Maintenance Adjustment

1. Bar the engine until “A” or 1-6 “VS” mark on the pulley, fig. 2-15 and 2-16, is aligned with the pointer on the gear case cover. In this position, both valve rocker levers for cylinder No.5 must be free (valves closed). The injector plunger for cylinder No.3 must be at top of its travel; if not, bar the engine 360 degrees, realign the mark with the pointer.

2. Set up ST-1170 Indicator Support with the indicator extension on the injector plunger top at No. 3 cylinder, Fig. 2-17. Make sure the indicator extension is secure in the indicator stem and not against the rocker lever.

Note: Cylinder No.3 for injector setting and cylinder No.5 for valve setting are selected for illustration purposes only. Any cylinder combination may be used as a starting point. See Table 2-3.

Table 2-3: Injector and Valve Set Position N-855 Engines

Bar in Direction	Pulley Position	Set Cylinder Injector	Valves
Start	A or 1-6VS	3	5
Adv.To	B or 2-5VS	6	3
Adv.To	C or 3-4VS	2	6
Adv. To	A or 1-6VS	4	2
Adv.To	B or 2-5VS	1	4
Adv. To	C or 3-4VS	5	1

3. Using ST-1193 Rocket Lever Actuator, Fig.2-18, or equipment, bar the lever toward the injector until the plunger is bottomed to squeeze the oil film from the cup. Allow the injector plunger to rise, then bottom again. Set the indicator at zero (0). Check the extension contact with the plunger top.

4. Bottom the plunger again, release the lever; the indicator must show travel as indicated in Table 2-4. Adjust as necessary.

5. If loosed, tighten the locknut to 40 to 45 ft-lbs [54 to 61 N*m] and actuate the injector plunger several times as a check of the adjustment. Tighten to 30 to 35 ft-lbs [41 to 47 N*m] when using ST-669 Adapter.

Table 2-4: Adjustment Limits Using Dial Indicator Method Inch [mm] N-855 Engines

Oil Temp.	Injector Plunger Travel Inch [mm]	Valve Clearance Inch [mm]
	Adj. Valve	Intake	Exhaust
Nt-855 (Big Cam only – Non Top-Stop
Cold	0.228 [5.79]	0.011 [5.79]	0.023 [0.58]
Note: Check engine dataplate for injector and valve setting.