COMPONENT DESCRIPTION AND INSTALLATION REQUIREMENTS

Individual components of the fuel system are described here more completely as to purpose, recommended features, and instal- lation requirements to achieve satisfactory performance and life.

Fuel Tank

It provides fuel storage and should have the following features:

Adequate size for the intended applica- tion. Rule of thumb for tank size with 25% reserve is:

0.056 2_____ hp (average)

2 _____ hours (between refills)

21.25 = _____ gal (U.S.)

0.27 2_____ kW (average)

2 _____ hours (between refills)

21.25 = _____ liters

Adequate structural strength to avoid fail- ure under application conditions which may include shock loading and steady vibration. Appropriate material. Zinc (galvanized or zinc-bearing materials such as brass) react with sulphur in fuel oil to form a sludge which is harmful to the engine’s fuel injection sys- tem. Steel, aluminum, stainless steel, or copper clad steel is used successfully. Expansion volume must be adequate to allow for expansion of stored fuel during temperature change. Allowance of 5% of tank volume is adequate. This can be pro- vided by extending the filler neck down into

the tank enough to create the required expansion volume. A small vent hole (about 0.19 in [4.81 mm] diameter) in filler tube, just below top of tank, is required to make this volume usable.

Venting to atmospheric pressure is neces- sary to prevent pressure or vacuum buildup. A large tank can be collapsed by vacuum or burst by pressure if not vented properly. Filler must be adequately sized and locat- ed for convenient filling. It should also be lockable. Fuel spillage must not reach hot parts. Also, fuel spillage should not reach items which can soak up or entrap fuel or be damaged by fuel.

Filler should be located near center of tank so that parking a mobile machine on a side tilt will not cause expanding fuel to back up into filler pipe and overflow. This will also help avoid spilling fuel from a full tank when operating on a grade.

Fuel tanks should be shielded or located away from major heat radiating sources such as hot exhaust manifolds and tur- bochargers. Also, the cooling fan blast picks up enough heat from the radiator to raise fuel temperatures significantly if the air is directed at the fuel tank. This will result in some power loss because of the heated, expanded fuel. Fuel level should not be above the fuel injectors on the engine to avoid possible seepage of fuel through a leaky injector into the cylinder (and then to the oil pan) during engine shutdown. Also, to avoid hard starting, the fuel level should not cause total suction lift of more than 12 ft (3.7 m). Much less is better.

A sloping bottom helps collect sediment and any major amounts of water, and a bottom drain is necessary to permit peri- odic removal of these contaminants.

Fuel supply pickup should be off of the bottom enough to leave 3% to 5% of the fuel in the tank. This should leave sediment and water in the tank until drained off peri- odically. The pickup line must rise upward through the top of the tank so that the con- nection to fuel lines is above the full level in the tank.

Fuel return line should normally enter the tank at the top and extend downward, exiting above the fuel level. Inlet and return lines should be separated in the tank by at least 12 in (304.8 mm) to avoid air pickup in the inlet line.

Baffles reduce sloshing and resulting air entrainment. They also prevent sudden shifts in the tank’s center of gravity, when in motion, as on a mobile machine.

Strong fastening of the fuel tank to the machine is essential. This is especially important on a mobile application where motion of a full tank generates sizeable forces. It is good practice to use some non- metallic cushioning material between the tank and support members to avoid fretting and wear on the tank.

Water Separator and Primary Filter Fuel system components can be damaged by water-caused corrosion or by the poor lubricating quality of water. For this reason separation and removal of water from the fuel is essential. Also, because water can collect and freeze at low points in fuel lines, filters, or other components that contain fuel, a water separator should be placed as close to the fuel tank as practical in a visi- ble, serviceable location. Usually, the sep- arator has a see-through feature that allows a quick visual check for presence of water and a quick-drain valve to let the water out. Because the compact sleeve metering injection pump on the 3208, 3304, and 3306 Engines uses fuel as a lubricant, it can be damaged more quickly by water than the scroll-type system.

However, any system can be damaged by water in the fuel; so the water should be removed. Fuel system damage by water is always the responsibility of the user. The water separator should be sized ade- quately to separate and store enough water between periodic drainings to pre- vent overfilling and water carryover into the engine’s fuel system.

The water separator should be mounted in a visible location. If the operator sees water, he is more likely to drain it out periodically. If the device is hard to see or difficult to ser- vice, it may not receive regular attention. A primary filter is not needed when a water separator is used as on the 3200 and 3300 Engines.

The installation should include valves which can isolate the separator and primary filter when the elements are changed.

Lines and Fittings

Pipes, hoses, and fittings must be mechan- ically strong, leak-tight, and resistant to deterioration due to age or environmental conditions. Sizing must be adequate to minimize flow loss. Routing must be cor- rect, and flex connections, such as hose assemblies, must isolate engine motion from the stationary members in the system. The fuel supply and return lines should be no smaller in size than the fittings on the engine. Fuel line pressure measured in the return line should be kept below 5 psi (34.5 kPa). A check valve can be used in the fuel return line. A shutoff valve should not be used, because damaging pressure would result if the valve were left closed when engine was started.

Black iron pipe is suitable for diesel fuel lines. Copper pipe or tubing may be sub- stituted in sizes of 0.5 in (12.7 mm) nomi- nal pipe size or less. Valves and fittings may be cast iron or bronze (not brass). Zinc plating or zinc as a major alloy should not be used with diesel fuel because of instability in presence of sulphur. The sludge formed by chemical action is extremely harmful to an engine’s internal components. Joints and fittings must be leak-tight to avoid entry of air into the suction side of the fuel system. A joint which is leak-tight to fuel can sometimes allow air to enter the fuel system, causing erratic running and loss of power. Pipe joint compound should be used on pipe threads, taking care to keep it out of the fuel system where it can cause damage.

Fuel lines should be routed to avoid for- mation of traps which can catch sediment or pockets of water which will freeze in cold weather.

All connecting lines, valves, and tanks should be thoroughly cleaned before mak- ing final connections to the engine. The entire fuel system external to the engine should be flushed prior to connection to engine and startup.

Fuel lines should be designed with the application in mind. Especially on mobile, off-highway equipment, effects of vibration, shock loads, and motion of parts should be considered. Fuel lines should be well routed and clipped, with flexible hose connections where relative motion is present. Lines should be routed away from hot parts, like manifolds and turbochargers, to avoid fuel heating and potential hazard if a fuel line should fail.

Transfer Pump

This pump delivers low pressure (15 psi to 30 psi [103 kPa to 207 kPa]) fuel from the tank to the injection pump housing reser- voir. It is a gear-type pump with some lim- ited priming capability when the pumping gears are full of fuel. This pump should be protected from abrasive wear and corrosion by a water separator or primary fuel filter. Secondary Filter

Because fuel injection pumps and injectors are precision devices with extremely close clearances between working parts, parti- cles which can cause damage must be removed in the secondary filter. This filter is standard equipment on all Cat Diesel Engines. When a secondary filter gets plugged, an engine typically loses power or may run erratically. The fuel pressure gauge will indicate low fuel pressure under these conditions. Filter media in Caterpillar fuel filters is developed and carefully con- trolled to conform with Cat specifications on filtration efficiency and durability. Use of filters of unknown capability may not pro- tect the precision fuel system from conta- mination.

Fuel Pressure Regulator

Somewhere in the fuel path, before or at the injection pump, there is a pressure regulat- ing valve which limits the pressure of fuel supplied to the injection pump housing reservoir. This pressure must be enough to fill the individual injection pump assemblies, but would become excessive if the transfer pump could not pump excess fuel through a relief circuit back to the fuel tank. A shutoff valve should never be placed in the fuel return line because pressure would quickly build to damaging levels. The return line also allows air to escape from the system.

Priming Pump

When a fuel system has air in it, the hand priming pump is used to fill the system with fuel and purge the air. Once this has been done, the priming pump will not likely be used again until the fuel system is emptied for adjustment or repair.

Injection Pump

Fuel is pumped at a very high pressure to each cylinder injector by individual injection pumps. For example, a six-cylinder engine has six separate injection pumps within the injection pump group. The fuel volume pumped on each stroke is controlled by the rack (scroll system) or sleeve shaft (sleeve- metered fuel system) which determines the effective pumping stroke. The governor controls the rack or sleeve shaft position, thereby controlling fuel delivery to produce a governed speed, regardless of load. Injection Lines

Individual fuel lines carry fuel at the very high pressure required for injection, from individual injection pumps to each cylinder injector. These lines are heavy-walled, strong, specially extruded tubing made only for this purpose. Because the injection lines carry such high pressure, they should not be bent or damaged during installation or operation.

Injectors

The purpose of the injector valve is to spray the correct pattern of atomized fuel into the combustion chamber (DI) or into the precombustion chamber (PC). It has a spring-loaded valve which requires that the pressure rise to some elevated level before valve opens at start of injection. This is necessary for precision-timed fuel delivery and assures a sharp cutoff of fuel at the end of each injection period.

Governor and Controls

The purpose of the governor is to control engine speed by regulating the amount of fuel injected. It does this by controlling the rack or sleeve shaft position. The speed control lever on the governor is positioned by the operator using some type of control lever, cable, or remote actuator (air, elec- tric, etc.).

Devices such as fuel-air ratio controls, shutdown solenoids, and manual shutoffs also operate on the governor which, in turn, operates on the rack or sleeve shaft. GOVERNORS

All engine models have hydra-mechanical speed droop governors standard on indus- trial models, except 3208 and 3300 Engines which have mechanical speed droop gov- ernors as standard. Both types contain mechanical ball-head-type speed govern- ing devices, but the hydra-mechanical gov- ernors use a pilot valve and servo system controlling flow of engine oil to provide the working force to move the rack.

Types of governors available for use on all Caterpillar Engines, except the 3208, are speed droop, isochronous, and electric load sharing. Only the speed droop-type is available on the 3208. The engine applica- tion determines which one should be used. Close regulation governors are required for some types of processing operations. For example, a forage harvester cutter head or a rock crusher must operate in a narrow speed bank for best results.

Sped Droop Governors

A speed droop governor’s full load speed is less than its no-load speed. This difference is called speed droop and is expressed as a percentage of full-load speed. For example, a governor with 10% regulation, or speed droop, with a full-load speed of 2000 rpm would have a no-load speed (high idle) of 2200 rpm.

The speed droop governors available on Cat Engines are not all the same in construc- tion, but their speed droop characteristics are similar. They are generally available in nominal 3% and 10% versions.

Engines equipped with speed droop gov- ernors can be shut down by moving the hand throttle beyond a detent into a fuel-off position. A manual shutoff shaft and provi- sions for mounting an optional DC shutoff solenoid are standard on most Cat Engines. The manual shutoff shaft can have a lever installed on it to provide a mechanical or pneumatic method of stopping the engine, whereas the solenoid option provides for remote electric shut down of the engine. Speed droop governors are recommended for most mechanical and torque converter drives where operation is characterized by varying speeds. If output shaft speed on a torque converter must be controlled or limited, an output shaft governor must be installed.

Constant speed applications, such as pumps and various processing operations, also use speed droop governors success- fully if the effect of speed variation due to load change is not significant.

When operated at less than rated full load speed, the governor speed droop percent- age increases. Governor springs can be changed to restore proper droop.

Isochronous Governors

Isochronous governors, usually referred to as “constant speed or zero percent speed droop,” are available on all Cat Engines except the 3208. Their no-load and full- load speeds are the same.

The isochronous governors used by Caterpillar are the Woodward PSG, UG8D (dial-type) and UG8L (lever-type), and EG3P-2301. These governors are serviced by Caterpillar.

Although these governors are isochronous, they can be adjusted to provide speed droop. The speed droop adjustment is exter- nal on the UG8D and newer PSG gover- nors. It is internal on the UG8L.

The PSG governor has its own oil pump but operates on engine oil. It is available for the smaller engines and can be sup- plied with an electric speed-changing motor for remote control.

The UG8D and UG8L governors, which have a self-contained oil pump and oil sup- ply, are available on the larger engines. The UG8D is available with a 24-32 Vdc, 100 VAC-50 Hz, 115 VAC-60 Hz, speed- changing motor and a 24-32 Vdc shut- down solenoid. The UG8L is available with a 10 psi to 60 psi (69 kPa to 414 kPa) air actuator. The PSG and UG8D are normally used for generator set applications. These governors and their applications are dis- cussed more fully, with pictures, in the Oil Field Application and Installation Guide.

Governor Selection Governor With

Speed Speed Droop 2301 2301 Droop Capability Load-Sharing Standby Governor* PSG UG8D UG8L Governor Governor

D399 X X X X X** G399 X X X X X** D398 X X X X X G398 X X X X X** D379 X X X X X G379 X X X X X** D353 X X X X X D349 X X X X** D348 X X X X** G342 X X 3412 X X X X 3408 X X X X 3406 X X X X 3306 X X 3304 X X 3208 X

**Speed droop available is dependent upon the specific engine. Contact your Caterpillar

Engine supplier for specifics.

**Standard equipment for standby automatic start-stop applications. Electric Load Sharing Governors

A Woodward 2301 electric load-sharing governor system is available on most Caterpillar Engines except the 3208s and 3300s. This governor is isochronous. It also has the ability to provide automatic and proportional load division between paralleled AC generators, even with differ- ent sized units, and still maintain isochro- nous speed.

An EG3P actuator is mounted on the engine, and the control box is mounted remotely. Refer to Generator Set Selection and Installation Guide for more complete infor- mation concerning electric governors. Governor Selection

The following two charts summarize gov- ernor configurations and their capabilities:

Governor Capabilities and Recommended Usage

2301 2301

Speed Isochronous Load- Speed Droop Governor Sharing Control

Governor PSG UG8D UG8L Governor Governor

Load X Sharing At Isochronous Speed Isochronous X X X X X Speed Droop X X X X X X Rheostat X X Speed Adjustment Electric X X X Motor Speed Adjustment (AC-DC) Air X X Throttle Speed Adjustment Shutdown by X Governor Throttle- Diesel Manual X X X X X Shutoff Plunger- Diesel DC Shutoff X X X X Solenoid- Diesel Variable X X X Speed Operation Constant X X X X X X Speed Operation Parallel X X X X Operation (DC or AC)

CONTROLS

Purpose — To input the governor with a correct speed signal, usually a mechanical motion, to result in desired engine speed. Description — Typically, the control sys- tem will consist of a single lever-linkage arrangement, or a push-pull cable which translates operator’s action to the governor speed control lever. Sometimes the speed control can also move the governor to shut-off position, but more typically, a sep- arate shut-off device (solenoid or mechan- ical linkage) is attached to the governor for this purpose.

Controls should be easy to use by the machine operator. They control engine speed and shut off fuel to stop the engine. Governor Force and Motion Data

The TIF contains information on (1) arc of motion and (2) force level required to oper- ate the governor speed control on each engine model. This allows the designer to select or design an appropriate cable con- trol, or some lever-link arrangement. Use of Control Cable

When there is relative motion between the engine and the machine, a cable control may be used to avoid transmitting unwant- ed motion to the governor control lever causing unacceptable speed fluctuation which can be confused with governor surge. Design for Linkage Over-Travel

Control mechanisms must be designed with a stop which prevents overloading the governor lever when it reaches its limit of travel. But this causes a problem when the stop on the control linkage is reached before full speed position of governor lever

is reached. This causes power complaints because the engine is prevented from operating at rated power, because the link- age did not allow the engine to develop rated speed.

The best approach is to use a springloaded break-over governor lever which accepts motion of the control linkage beyond the travel of the governor shaft. Then it is easy to adjust correctly and visually check that the governor speed control lever will travel its full range.

Engine Shutdown Control

Engine shutdown is done by shutting off fuel supply in some manner. Usually this is done with a direct mechanical connection which pulls the rack to shutoff, or with a solenoid which does the same thing. Safety shutoffs are discussed more com- pletely in another chapter.

FUELS

Use clean fuel meeting Caterpillar’s recom- mendations for best service life and perfor- mance. Anything less is a compromise, and