D346 MARINE ENGINE Caterpillar


Fuel System

Usage:



Fuel

Check the fuel supply. Order fuel as required. See Lubrication and Maintenance Chart for fuel recommendations.

Fuel Tank

Open the fuel tank drain valve to drain water and sediment from the fuel tank. To minimize water contamination, fill the fuel tank in the late afternoon if possible. As the fuel is consumed, air with some humidity must replace the fuel in the tank. By filling the tank in the late afternoon, this humid air is expelled before the moisture can condense on the cool inside walls of the fuel tank.

Fuel Filters

Draining Water And Sediment

1. Close the fuel supply valve if the fuel tank is located above the level of the fuel filters.
2. Remove the drain plug from one cover of the fuel filter housing. Drain water and sediment from the filter housing.


REMOVING FILTER HOUSING DRAIN PLUG

3. Install the drain plug.
4. Remove the drain plug from the other cover of the fuel filter housing.
5. Drain water and sediment from that end.
6. Install the drain plugs and vent plug.
7. Prime the fuel system.

Priming The Fuel System

1. Open the fuel supply line valve.
2. Move the governor control lever to the shut-off position.
3. Turn the pump handle knob counterclockwise; release the lock plate from the retainer on the fuel priming pump.
4. Operate the fuel priming pump until the air in the fuel system has been pumped through the fuel return line to the fuel tank.

If desired, the fuel return line connection may be loosened. When a solid stream of fuel flows from the connection, air has been expelled and the connection can be tightened.


OPERATING THE PRIMING PUMP

5. Secure the pump handle: Turn the lock plate vertically, turn the pump handle knob clockwise until the lock plate contacts the plate retainer.
6. Start the engine. If the engine misfires or smokes, loosen a fuel injection line nut, and allow the fuel to flow until free of air bubbles. Tighten the line nut; open the next line nut and continue venting each successive line.


LOOSENING FUEL LINE NUT AT THE NOZZLE

Checking Fuel Pressure Gauge

With engine running, the fuel pressure gauge should register in the NORMAL range. If the gauge registers in the OUT range, service the fuel filter elements.

Cleaning Primary Filter Element

1. Stop the engine.
2. Close the diesel fuel supply line valve.
3. Loosen the nut on the cover and remove the case.


REMOVING PRIMARY FUEL FILTER

4. Remove the filter element. Clean the element and case in kerosene or diesel fuel.
5. Inspect and install the upper and lower cover gaskets. Install new gaskets if necessary.
6. Install the cleaned filter element and case.
7. Open fuel supply line valve.
8. Prime the fuel system.

Installing Final Fuel Filter Elements

If your engine is equipped with a standard fuel filter system, read the following instructions. If your engine is equipped so as to permit changing the fuel filter elements while the engine is operating, read the topic, "DUPLEX FUEL FILTER SYSTEM".

1. Close the fuel supply line valve.
2. Remove the drain plug in each cover. Drain the fuel filter housing.


DRAIN PLUG

3. Remove both end covers.


REMOVING FILTER COVER

4. Push the used filter elements from left to right through the filter housing.


REMOVING USED FILTER ELEMENTS

5. Wipe sediment from inside the filter housing; use a clean cloth.
6. Inspect the cover gaskets. Install new gaskets if necessary.
7. Install the right cover. Install new filter elements.


INSTALLING NEW FILTER ELEMENTS

8. Install the left cover.
9. Install the drain plugs in the covers.
10. Open the fuel supply line valve.
11. Prime the fuel system.

Duplex Fuel Filter System

During normal engine operation, the selector lever should be positioned in the "MAIN FILTER RUN-AUX. OFF" position. The fuel will then be filtered by the main filter elements located in the right hand side of the fuel filter housing. Two filter elements, located in the left hand side of the fuel filter housing, are auxiliary filter elements. When standing at the flywheel and looking forward, the right hand side is to the right, and the left hand side is to the left.

When the fuel pressure gauge indicates minimum acceptable pressure (20 psi), the main fuel filter elements must be changed. The fuel must be filtered by the two auxiliary filter elements while the main filter elements are being changed.

1. Move the selector lever to the AUX. VENT-MAIN RUN position.

Any air in the auxiliary filter housing will be vented back to the fuel tank while the main fuel filters will continue to filter the diesel fuel.


"AUX. VENT-MAIN RUN" POSITION

2. After air bubbles are no longer visible in the sight gauge, move the selector lever to the AUX. FILTER RUN-MAIN OFF position.


"AUX. FILTER RUN-MAIN OFF" POSITION

The auxiliary filter elements now filter the diesel fuel instead of the main filter elements.

3. Remove the drain plug from the right hand filter housing (as viewed from the flywheel looking forward) and remove the vent plug from the right hand cover. Drain that side of the filter housing.


NOTICE

Be sure you are removing the drain plug from the right hand filter cover. As soon as the drain plug is loosened, fuel will spray out under high pressure for a short time until pressure drops in the housing. If spraying of fuel continues, you are removing the wrong drain plug and preparing to remove the wrong cover.



RIGHT COVER AND DRAIN PLUGS

4. Remove the right hand cover. Remove the five filter elements.


REMOVING MAIN FILTER ELEMENTS

5. Check inside the filter housing for sediment. Remove sediment with a clean cloth.
6. Install new filter elements.
7. Inspect the cover gasket. Install a new gasket if necessary.
8. Install the cover.
9. Install the vent plug in the cover and the drain plug in the housing.
10. Observe the fuel pressure gauge reading. The gauge reading will indicate the condition of the auxiliary filter elements. If the fuel pressure gauge indicates minimum acceptable operating pressure (20 psi), service these auxiliary elements as described in the following topic.
11. Move the selector lever to the MAIN VENT-AUX. RUN position. While the auxiliary filter elements filter the fuel, the main filter housing will fill with fuel.


"MAIN VENT-AUX. RUN" POSITION

If the fuel filter elements are changed while the engine is stopped, prime the fuel system by pumping the fuel priming pump until bubbles are no longer visible in the bleed window.


FUEL PRIMING PUMP

12. After air bubbles are no longer visible in the bleed window, move the selector lever to the MAIN FILTER RUN-AUX. OFF position. The main filters will now be filtering the fuel.


"MAIN FILTER RUN-AUX. OFF" POSITION

13. Check for fuel leaks.

Installing Auxiliary Fuel Filter Elements

When the fuel is being filtered by the auxiliary fuel filter elements and the fuel pressure gauge indicates minimum acceptable pressure (20 psi), the auxiliary fuel filter elements must be changed. This can be done with the engine running and with the selector lever in the MAIN FILTER RUN-AUX. OFF position.


"MAIN FILTER RUN-AUX. OFF" POSITION

1. Remove the drain plug from the left hand housing, (as viewed from the flywheel looking forward), and remove the vent plug from the left hand cover. Drain that side of the filter housing.


NOTICE

Be sure you are removing the drain plug from the left hand filter cover. As soon as the drain plug is loosened, fuel will spray out under high pressure for a short time until pressure drops in the housing. If spraying of fuel continues, you are removing the wrong drain plug and preparing to remove the wrong cover.



LEFT COVER AND DRAIN PLUG

2. Remove the left hand cover. Remove the two filter elements.


REMOVING LEFT COVER

3. Check inside the filter housing for sediment. Remove sediment with a clean cloth.
4. Install new filter elements.


INSTALLING NEW FILTER ELEMENTS

5. Inspect the cover gasket. Install a new gasket if necessary.
6. Install the cover.
7. Install the drain plug in the cover.
8. Move the selector lever to the AUX. VENT-MAIN RUN position. While the main filter elements filter the fuel, the auxiliary filter housing will fill with fuel.


"AUX. VENT-MAIN RUN" POSITION

If the fuel filter elements are changed while the engine is stopped, prime the fuel system by pumping the fuel priming pump until bubbles are no longer visible in the bleed window.


OPERATING FUEL PRIMING PUMP

9. After air bubbles are no longer visible in the bleed window, move the selector lever to the AUX. FILTER RUN-MAIN OFF position. Check for fuel leaks.


"AUX. FILTER RUN-MAIN OFF" POSITION

10. After determining the auxiliary filters are ready for use, move the selector lever to the MAIN FILTER RUN-AUX. OFF position. The main filters will again be filtering the fuel.


"MAIN FILTER RUN-AUX. OFF" POSITION

11. When the fuel pressure gauge indicates minimum acceptable pressure (20 psi) with the engine running, the main fuel filter elements must be changed. See the topic, INSTALLING NEW FINAL FUEL FILTER ELEMENTS.

Running On Both Filter Systems

The engine can run using all of the filter elements in both fuel systems at the same time. Move the selector lever to the BOTH FILTERS RUN position. This will allow additional running time when both filter systems could be approaching a plugged condition as indicated by the fuel pressure gauge. As soon as possible, change all elements in both filter systems.


"BOTH FILTERS RUN" POSITION

Woodward UG8 Governor

Checking Governor Oil Level

1. Check the governor oil level sight gauge.
2. Maintain the oil level between the ADD and FULL marks. Add oil as required. See Lubrication and Maintenance Chart for proper oil.


CHECK OIL LEVEL AND FILL

Changing Governor Oil

1. Move the governor control lever to the shut-off position.
2. Shut off the fuel tank fuel supply valve.
3. Disconnect the ground cable from the battery.

------ WARNING! ------

Be sure the engine cannot be started while work is being done. This is very important when the engine is equipped with an Automatic Start-Stop System.

------WARNING!--------
4. Disconnect the governor linkage from the governor.
5. Disconnect the governor synchronizing motor wires.


DISCONNECT SYNCHRONIZING MOTOR

6. Remove the governor from the engine.
7. Remove the governor cover.


REMOVING GOVERNOR COVER

8. Turn the governor upside down and drain the oil.
9. Flush the governor with clean diesel fuel or kerosene.
10. Install the governor on the engine.
11. Fill the governor, with clean oil, to the FULL mark on the sight gauge. See Lubrication and Maintenance Chart for proper oil.
12. Connect the governor linkage.

------ WARNING! ------

Before starting the engine, check to be sure the governor linkage has been connected to the governor.

------WARNING!--------
13. Connect the ground cable to the battery.

Bleeding Governor

1. Start the engine and allow the engine to reach normal operating temperature.
2. Loosen the nut on the side of the governor which holds the compensation adjusting pointer.
3. Manually move the pointer to the extreme upper position and tighten the nut. This will allow the governor to be purged of air.


SETTING POINTER AT UPPER POSITION

4. Remove the plug from the base of the governor.
5. Using a wide blade screwdriver, engage the wide shallow screwdriver slot and turn the needle valve 3 or more turns counterclockwise.


OPENING NEEDLE VALVE

6. Allow the engine to surge for approximately 30 seconds.
7. Loosen the nut and move the compensation adjusting pointer to the extreme downward position. Tighten the nut.
8. Slowly turn the needle valve (wide shallow slot) clockwise until the surging stops.
9. It should now take less than one turn from this point to close the valve completely.
10. Open the valve to the same position where the surging had stopped.
11. Manually move the governor linkage to disturb the engine speed.


MANUALLY CHANGING ENGINE SPEED

If the engine speed stabilizes, and the needle valve is only 1/2 to 3/4 turn open, the governor is properly adjusted. Install the base plug.

If more than a 3/4 turn is required to stop the engine from surging, proceed with the following steps.

12. Raise the pointer two divisions on the pointer scale.
13. Engage the wide shallow slot and turn the needle valve counterclockwise 3 or more turns.
14. Allow the engine to surge approximately 30 seconds.
15. Gradually turn the needle valve clockwise until surging just stops.
16. Note the portion of a turn required to close the needle valve.
17. Open the valve exactly to the same position surging stopped.
18. Manually move the governor linkage to disturb the engine speed. The engine speed should stabilize with the needle valve opened 1/2 to 3/4 turn.
19. A valve opened less than 1/2 of a turn produces a slow response to load changes. A valve opened more than 3/4 of a turn produces excessive speed response to load change. If the engine does not stabilize between 1/2 to 3/4 turn open, raise the pointer two divisions and repeat steps 12 through 19.
20. When the engine speed stabilizes, install the base plug.

Lubricating The Governor Synchronizing Motor

Fill the cup on top of the motor with clean oil. See Lubrication and Maintenance Chart for proper oil.


LUBRICATING ELECTRIC MOTOR

Fuel Priming Pump Lubrication

Earlier drum type fuel priming pumps require the pump shaft bearings be lubricated with grease. The priming pump shaft of the D346, D348, D379 and D398 Engines requires 1 or 2 strokes of a grease gun. Each bearing supporting the D399 pump lever shafting requires 1 or 2 strokes of a grease gun.

Lubricate the fuel priming pump shaft bearing with grease:

1 or 2 strokes, 1 fitting in the lever bearing.


LUBRICATING FUEL PRIMING PUMP BEARINGS

D399: 1 or 2 strokes, 2 fittings; 2 bearings:


LUBRICATING FUEL PRIMING PUMP BEARINGS

The horizontal type priming pump on top of the fuel filter housing of the D349 and the later D346, D348, D379, D398 and D399 Engines does not require servicing.

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