3406 MARINE ENGINE Fuel System Caterpillar

Fuel System
1.1. Fuel
2.2. Diesel Fuel
3.2. Fuel Tank Maintenance
4.2. Checking Fuel Pressure
5.1. Primary Filter Element
6.2. Cleaning Primary Fuel Filter
7.1. Fuel Filter
8.2. Changing Filter
9.1. Priming Pump
10.2. Priming the Fuel System
11.1. Woodward PSG Governor
12.2. Lubricating Governor Control Linkage
13.2. Lubricating Synchronizing Motor


Diesel Fuel

See the Lubrication and Maintenance Chart for distillate fuel recommendations to use when ordering fuel.

Fuel Tank Maintenance

1. Check the fuel level daily.
2. Fill the fuel tank as required. If possible, fill the tank before evening.

As fuel is used, air with some humidity must replace the fuel in the tank. As the fuel tank cools at night, this moisture may condense on the inside walls of the tank and drop into the remaining fuel and contaminate it.

By filling the tank before evening, there will be that much less air and humidity in the tank to condense.

3. Periodically open the fuel tank drain valve. Drain the water and sediment from the fuel tank to prevent fuel contamination and poor engine performance.

Checking Fuel Pressure

With the engine running, the fuel pressure gauge should register in the NORMAL range. Observe the gauge reading frequently. If the gauge indicates in the OUT range, clean the primary filter element, if so equipped; or change the fuel filter element.

Primary Filter Element

Cleaning Primary Fuel Filter

1. Stop the engine.
2. Close the diesel fuel supply line valve.
3. Loosen the cover nut, and remove the housing and element.

4. Remove the element from the housing; and clean them both in solvent.

5. Inspect the upper and lower cover gaskets. Install new gaskets if necessary.

6. Install the cleaned filter element and case.

7. Open the fuel supply line valve.
8. Prime the fuel system as instructed.

Fuel Filter

Changing Filter

1. Stop the engine.
2. Close the diesel fuel supply valve.
3. Wipe the top of the filter element and filter base.

4. Unscrew and remove the filter.

5. Be certain the filter gasket did not remain attached to the filter base: Leaking between the new and old filter gaskets would result.

6. Clean the gasket sealing surface of the filter base.

7. Lubricate the new filter gasket with clean diesel fuel.
8. Install the new filter: Hand tighten the filter. When the engine is running, check for fuel leaks; and if necessary, tighten the filter by hand until leaking stops.

9. Open the fuel supply line valve.
10. Prime the fuel system as instructed.

Priming Pump

Priming the Fuel System

If air is trapped in the fuel system, the diesel engine will either not start, or will misfire.

1. Move the governor control lever to the shut-off position.
2. Loosen the inlet fuel line to the fuel pump housing.


Operate the priming pump only after a fuel line has been loosened.

3. Turn the pump counterclockwise from the locked position.

4. Operate the fuel priming pump with rapid strokes until the stream of fuel pumped out is free of air bubbles.
5. Push in on the pump and turn clockwise to lock the pump in the locked position.
6. Tighten the loosened fuel line.

7. Start the engine.

If the engine misfires or smokes:

8. Loosen a fuel injection line nut. Allow the fuel to flow until free of air bubbles.

9. Tighten the line nut; open the next line nut.
10. Vent each fuel line in similar manner until the engine is running smoothly.


Avoid bleeding excessive amounts of fuel.

Woodward PSG Governor

Lubricating Governor Control Linkage

The governor control linkage has two fittings. Lubricate each fitting with two strokes of MPGM grease.

Lubricating Synchronizing Motor

Fill the oil cup on the synchronizing motor with clean engine oil; with same viscosity as used in the engine.