Caterpillar Diesel Engines can operate effectively in cold weather. However, engine operation in cold weather is dependent on the type of fuel used and how well the fuel moves through fuel related components. The purpose of this section is to explain some of the problems and steps that can be taken to minimize fuel problems during cold weather operation [below 5°C (40°F)].

Radiator Restrictions
Caterpillar discourages the use of air flow restriction devices mounted in front of radiators. Air flow restriction can cause higher exhaust temperatures, power loss, excessive fan usage, and a reduction in fuel economy.

If an air flow restriction device must be used, the device should have a permanent opening directly in line with the fan hub. The device must have a minimum opening dimension of at least 770 cm2 (120 in2).

A centered opening, directly in line with the fan hub, is specified to provide sensing when viscous fan drives are used and/or to prevent an interrupted air flow on the fan blades. Interrupted air flow on the fan blades could cause a fan failure.

Air temperature in the inlet manifold should not exceed 65°C (150°F). Temperatures exceeding this limit can cause power loss and potential engine damage. Caterpillar recommends an inlet manifold temperature device, such as a light indicator, buzzer, etc., set at 65°C (150°F) and/or installation of an inlet air temperature gauge.

This temperature provides engine protection for full restriction device closure. This temperature can also serve as a diagnostic tool for a malfunction of the charge air cooling system. It is not anticipated that a temperature of 65°C (150°F) will be encountered under normal operating conditions.

Fuel and the Effect from Cold Weather
The two types of diesel fuel available for your engine are typically grades No.1 and No.2. No.2 diesel fuel is the most commonly used fuel. No.1 diesel fuel, or a blend of No.1 and No.2, is best suited for cold weather operation.

Quantities of No.1 diesel fuel are limited, and generally only available during the winter months in the colder climates. During cold weather operation, if No.1 fuel is unavailable, it may be necessary to use No.2 diesel fuel.

There are three major differences between No.1 and No.2 diesel fuel. No.1 diesel fuel has:

* a lower cloud point
* a lower pour point
* a lower BTU (kJ) (heat content) rating per unit volume of fuel than the average No.2 diesel fuel
When using No.1 diesel fuel, you may notice a drop in power and fuel efficiency. You should not experience any other operating effects.

The cloud point is the temperature at which a cloud or haze of wax crystals begins to form in the fuel and cause fuel filters to plug. The pour point is the temperature which diesel fuel begins to thicken and be more resistant to flow through fuel pumps and lines.

Be aware of these fuel values when purchasing your diesel fuel. Anticipate the average outside (ambient) temperature for the area your engine will be operating. Engines fueled in one climate may not operate satisfactorily if moved to another because of problems that result from cold weather.

Before troubleshooting for low power or poor performance in winter months, check the type of fuel being used.

When No.2 diesel fuel is used: starting aids, engine oil pan heaters, engine coolant heaters, fuel heaters, and fuel line insulation also provide a means of minimizing starting and fuel problems in cold weather.

Fuel Related Components in Cold Weather

Fuel Tanks
Condensation can form in partially filled fuel tanks. Top off fuel tanks before leaving overnight.

Fuel tanks should contain some provision for draining water and sediment from the bottom of the tanks. Some fuel tanks use supply pipes that allow water and sediment to settle below the end of the fuel supply pipe.

Some fuel tanks use supply lines that take fuel directly from the bottom of the tank. If equipped with this system, regular maintenance of the fuel system filter(s) is important.

Check the fuel level in the day tank daily by observing the sight gauge. Drain the water and sediment from any fuel storage tank weekly, at the oil change period, and before the fuel tank is refilled. This will help prevent water and/or sediment from being pumped from the fuel storage tank into the engine fuel tank.

Fuel Filters
A primary fuel filter is installed between the fuel tank and the engine fuel inlet. After changing the fuel filter(s), always prime the fuel system (if equipped with a priming pump) to remove air bubbles from the system.

The micron rating and location of a primary fuel filter is important in cold weather operation. The primary fuel filter and the fuel supply line to the primary fuel filter are the most common components affected by cold fuel.

The micron rating of the primary fuel filter should only be fine (low) enough to protect the fuel transfer pump. A very fine (low micron rating) primary filter, can be more easily plugged by wax in cold weather.

NOTE: Refer to the Parts Manual for this engine to determine the part numbers required for the fuel filters.

Fuel Heaters
Fuel heaters prevent fuel filters from plugging in cold weather due to waxing. A fuel heater should be installed so that the fuel is heated before it enters the primary fuel filter.

Select a fuel heater that is mechanically simple, yet adequate for the application. The fuel heater should also prevent overheating of the fuel. High fuel temperatures reduce engine performance and power availability. Choose a fuel heater with as large a heating surface as practical. Small heaters can be too hot in their limited surface area.

Disconnect or deactivate the fuel heater in warm weather.

NOTE: Only thermostatically controlled or self-regulating fuel heaters should be used with this engine. Non-thermostatically controlled fuel heaters can heat the fuel in excess of 65°C (149°F). A loss of engine power can occur if the fuel supply temperature exceeds 37°C (100°F).

NOTE: Heat exchanger-type fuel heaters should have a bypass provision to prevent overheating of the fuel in warm weather operation.

The following fuel heaters are recommended for use with Caterpillar engines.

* 7C-3557 Fuel Heater
* 7C-3558 Fuel Line Heater Kit
For further information on fuel heaters, contact your Caterpillar dealer.

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