Cummins Engine Warm-Up

When the engine is started it takes a while to get the lubricating oil film re-established between shafts and bearings and between pistons and liners. The most favorable clearances between moving parts are obtained only after all engine parts reach normal operating temperature. Avoid seizing pistons in liners and running dry shafts in dry bearings by bringing the engine up to operating speed gradually as it warms up.

On some emergency equipment (such as fire pump engines) warm-up may not be necessary due to the equipment being housed inside a heated building. For an engine starting with a parasitic load such as a fire pump , the coolant temperatures must be a minimum of 120°F[49°C].

Engine Speeds

All Cummins engines are equipped with governors to prevent speeds in excess of the minimum or predetermined lower speed rating.

The governor has two functions: First ,it provides the fuel needed for idling when the throttle is in the idle position .Second ,it overrides the throttle and shuts off the fuel if the engine rpm exceeds the maximum rated speed.

Speeds listed in Table 1-1 are for engines rated at maximum rpm and fuel rate. 

Note: Engines in many applications are applied at a lower than maximum rated speed; check the serial data plate. Power generator units are pre-set to operate at a specific governed rpm.

Oil Temperature

The oil temperature gauge normally should read between 180°F[82°C]  and 225°F[107°C]. Under full load conditions an oil temperature of 240°F[116°C]for a short period is not cause for alarm. Caution: Any sudden increase in oil temperature which is not caused by a load increase is a warning of possible mechanical failure and should be investigated at once.

During the warm-up period, apply the load gradually until the oil temperature reaches the 140°F[60°C]. While the oil is cold it does not do a good job of lubricating. Continuous operation or long periods of idle with oil temperatures below140°F[60°C]may cause crankcase dilution and acids in the lubricating oil which quickly accelerate engine wear.

Water Temperature

A water temperature of 160°to200°F[71°to93°C] is the best assurance that the working parts of the engine have expanded evenly to the most favorable oil clearances. Maximum engine coolant temperatures should not exceed 200°F[93°C].

Keep the thermostats in the engine during summer and winter avoid long periods of idling and take the necessary steps to keep the water temperature up to a minimum of 160°F[71°Cl.If necessary in cold weather, use radiator shutters or cover a part of the radiator to prevent overcooling.

Oil Pressure

Normal engine oil pressures at 225°F[107°C]oil temperature are listed in Table 1-2.

Note: Individual engines may vary from the above normal pressures. Observe and record the pressure when the engine is new to serve as a guide for an indication of progressive engine condition (High oil pressure during start-up is not cause for alarm.)For record purposes these readings are more accurate and reliable when taken immediately after an oil change.

High Altitude Operation

Some engines, particularly naturally aspirated lose horsepower when they are operated at high altitude because the air is too thin to burn as much fuel as at sea level. This loss is about 3 percent for each 1000 ft [304.8 m] of altitude above sea level for a naturally aspirated engine. Operate the engine using a lower power requirement at high altitude to prevent smoke and over-fueling.

Power Take-Off Application With PT(type G)

VS Fuel Pump

The VS fuel pump governor lever is used to change the standard governed speed of the engine from rated speed to an intermediate power take-off speed.

When changing from the standard speed range to the power take-off speed with the engine idling on standard throttle ,operate as follows :

1. Place the VS speed control lever in the operatingposition.
2. Lock the standard throttle in the full-open position.
3. Engage the power take-off

To return to standard throttle:

1. Disengage the power take-off
2. Return the standard throttle to the idle position.
3. Lock the VS speed control lever in the maximumspeed position.