3406E Truck Engines Caterpillar

Either too much fuel or not enough fuel for combustion can be the cause of a problem in the fuel system. Often, work is done on the fuel system when the problem is really with another part of the engine. Excessive smoke from the exhaust is a difficult problem. Excessive smoke that comes from the exhaust can be caused by a worn unit injector. Excessive smoke can also be caused by one or more of the reasons that follow:

• There is not enough air for good combustion.

• There is an overload during a high altitude condition.

• There is oil leakage into the combustion chamber.

• There is not enough compression.

• The fuel injection timing is incorrect.

Procedure for Fuel Priming

Illustration 1	g00294863
Fuel system components (left side view) (1) Fuel return line from the cylinder head (2) Fuel priming pump (3) Fuel filter base (4) ECM (5) Fuel supply line to the cylinder head (6) Fuel transfer pump (7) Fuel filter (8) Air purge cap

Illustration 2	g00294865
Fuel system components (front view) (9) Air purge plug (10) Fuel return (11) Fuel inlet

Note: If the fuel system runs dry of fuel or air is introduced into the system, the following procedure must be followed.

1. Loosen the air purge cap (8) .

2. Unlock and operate the fuel priming pump (2) until fuel appears at the air purge cap (8) . Tighten the air purge cap (8) .

3. Loosen the air purge plug (9) for two turns. Continue operating the fuel priming pump (2) until fuel appears at the air purge plug (9) . Tighten the air purge plug (9) .

4. Continue operating fuel priming pump (2) until a resistance is felt. Push in and lock the hand priming pump.

5. Once the system is pressurized, crank the engine as soon as possible. The engine should start within 15 seconds. If the engine does not start after 30 seconds, stop cranking the engine. A period of 2 minutes is needed for the starter to cool before proceeding.

6. If the engine does not start, repeat the procedure.

Fuel System Inspection

A problem with the components that send fuel to the engine can cause low fuel pressure. This can decrease engine performance.

1. Check the fuel level in the fuel tank. Check the vent in the cap for the fuel tank for dirt.

2. Check the fuel lines for fuel leakage. Check the fuel lines for a worn bend or a restriction. Check that the fuel return line has not collapsed within the sections that are exposed to heat.

3. Install a new fuel filter.

4. Remove any air that may be in the fuel system. Refer to the topic "Procedure for Fuel Priming" in this service manual.

Fuel System Pressure

The typical fuel pressure of the engine at operating temperature can vary. At low idle, the fuel pressure can be 538 kPa (78 psi). At high rpm, the fuel pressure can be 641 kPa (93 psi).

The performance of the unit injector deteriorates when the fuel pressure drops below 241 kPa (35 psi). Low-power complaints and erratic operation can occur in this situation. Check for a plugged fuel filter or air in the fuel lines as possible causes for these complaints before replacing fuel system components.

Fuel Pressure

Table 1

Required Tools
Part Number	Part Name	Quantity
1U-5470 or 198-4240	Engine Pressure Group or (Indicator Group)	1

Illustration 3	g00294866
1U-5470 Engine Pressure Group

To check the fuel transfer pump pressure, remove the plug from the fuel filter base. Install a pressure gauge, and start the engine.

The 1U-5470 Engine Pressure Group can be used to check the fuel pressure of the engine. The engine pressure group includes Special Instruction, SEHS8907. This instruction provides information about the usage of the group.

Unit Injector Adjustment

Table 2

Required Tools
Part Number	Part Name	Quantity
9U-7227	Injector Height Gauge	1

Illustration 4	g00294868
Injector mechanism (1) Rocker arm (2) Adjusting screw (3) Locknut (4) 9U-7227 Injector Height Gauge

To make an adjustment to the unit injector, turn the adjusting screw in the rocker arm. The unit injector adjustment can be made by using the procedure that follows:

1. Put the number 1 piston at top center (TC) on the compression stroke. Refer to "Top Center Position For Number 1 Cylinder".

2. The fuel injector tool (4) is used to obtain a dimension of 78.0 ± 0.2 mm (3.07 ± 0.01 inch). The dimension is measured from the top of the unit injector lifter to the machined ledge of the fuel injector body.

3. Hold the adjusting screw in this position and tighten the locknut (3) to a torque of 100 ± 10 N·m (74 ± 7 lb ft).

4. Make an adjustment to the unit injectors on cylinders 3, 5, and 6.

5. Remove the timing bolt. The flywheel is then turned 360 degrees in the direction of engine rotation. The direction of engine rotation is a counterclockwise direction. This will put No. 1 piston at top center (TC) on the exhaust stroke.

6. Make an adjustment to the unit injectors on cylinders 1, 2, and 4.

7. Remove the timing bolt from the flywheel after all the unit injector adjustments have been made. Reinstall the timing cover.

Checking Engine Cylinders Separately

The engine utilizes Unit Injectors, which are mechanically actuated and electronically energized. The ECAPsystem can be used to cut out injectors individually. This will determine the misfire problems of individual cylinders.

Make reference to Electronic Troubleshooting. This section describes the testing procedure.

Static Check Of The Timing Gear Position

Illustration 5	g00294869
Front gear group (1) Timing marks (2) Camshaft gear (3) Adjustable idler gear (4) Idler gear (5) Cluster gear (6) Timing marks (7) Crankshaft gear (8) Oil pump gear

The correct fuel injection timing and the valve mechanism operation are determined by the synchronization of the front gear group. The timing marks (1) and (6) are aligned in order to provide the correct relationship between the piston and the valve movement.

Timing Procedure Using Gear Lash

Required Parts

Table 3

Part Number	Description
374-3473	Gear Segment Tool

Procedure

Note: The rocker arm bolts must be loosened to remove preload from the camshaft.

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Illustration 6	g02685416
Front cover is removed.

1. With the front cover removed, remove bolts (3) , plate (2) , and adjustable idler gear (1) .

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Illustration 7	g02686407

2. Loosen one bolt and two nuts (4) that secure the stub shaft. Remove the remaining three nuts. The one bolt and two nuts (4) can still be accessed when the gear segment tool is installed.

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Illustration 8	g03320498
(5) Timing marks (6) 374-3473 Gear Gauge

3. With the flywheel pinned at TDC for cylinder one, align timing marks (5) .

4. Install the cam gear backlash tool onto the stub shaft, as shown. Both sides of the gear segment tool should be engaged with the corresponding gear, as shown. Hand tighten the one bolt and two nuts enough so that slight resistance is felt if the stub shaft is rotated.

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Illustration 9	g02688245

5. Measure the backlash between camshaft gear (2) and gear segment tool (3) . When the gear segment tool is held stationary, the backlash between the gears is 0.3556 ± 0.254 mm (0.0140 ± 0.010 inch). Lightly tap the stub shaft with a soft mallet to move the gear segment tool closer to the cam gear or further away from the cam gear as necessary to increase or decrease the amount of backlash.

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Illustration 10	g02688540

6. Once the proper backlash is obtained, tighten the nuts and the bolt (4) to a torque of 55 ± 10 N·m (41 ± 7 lb ft).

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Illustration 11	g02688598

7. Remove the cam gear backlash tool and tighten the remaining three nuts to 55 ± 10 N·m (41 ± 7 lb ft).

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Illustration 12	g02688636

8. Install idler gear (1) . Verify that the correct amount of backlash is still correct, and the mark on the camshaft gear is still aligned with the mark on the front housing.

9. Install plate (2) . Before installing bolts (3) , clean the bolts with a wire brush to remove the old thread lock compound. Apply Loctite242 to the threads of the bolts and install the bolts. Then, tighten to the proper torque.

10. Install the front cover. Refer to Disassembly and Assembly, "Housing (Front) - Install".

Top Center Position For No. 1 Cylinder

Table 4

Required Tools
Part Number	Part Name	Quantity
9S-9082	Engine Turning Tool	1

The No. 1 piston at top center (TC) on the compression stroke is the starting point of all timing procedures.

Note: Some engines have two threaded holes in the flywheel. These holes are in alignment with the holes with plugs in the left and right front of the flywheel housing. The two holes in the flywheel are at a different distance from the center of the flywheel so the timing bolt cannot be put in the wrong hole.

Illustration 13	g00294875
Locating top center (Left Side Of Engine) (1) Timing bolt (2) Timing bolt location (3) Cover

Illustration 14	g00294876
Locating top center (Right Side Of Engine) (4) Timing bolt location.

1. The timing bolt (1) is a cover bolt. The timing bolt can be installed in either the left side of the engine at location (2) or in the right side of the engine at the timing bolt location (4) . Remove both bolts (1) and cover (3) from the flywheel housing. Remove the plug from the timing hole in the flywheel housing.

2. Put the timing bolt (1) (long bolt that holds the cover on the flywheel housing) through the timing hole in the flywheel housing. The 9S-9082 Engine Turning Tool and a 1/2 inch ratchet wrench are used to turn the engine flywheel in the direction of normal engine rotation. Normal engine rotation is in a counterclockwise direction, when the engine is viewed from the rear of the engine. Turn the engine flywheel until the timing bolt engages with the threaded hole in the flywheel.

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Illustration 15	g00294877
Using 9S-9082 Engine Turning Tool (1) Timing bolt (5) 9S-9082 Engine Turning Tool

Note: If the flywheel is turned beyond the point of engagement, the flywheel must be turned in the opposite direction of normal engine rotation approximately 45 degrees. Then turn the flywheel in the direction of normal rotation until the timing bolt engages with the threaded hole. This procedure eliminates the backlash that will occur within the gears when the No. 1 piston is put on top center.

3. Remove the front valve cover from the engine.

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Illustration 16	g00294878
Checking No. 1 Inlet And Exhaust Valves (typical example)

4. The inlet and exhaust valves for the No. 1 cylinder are fully closed if the No. 1 piston is on the compression stroke and the rocker arms can be moved by hand. If the rocker arms cannot be moved and the valves are slightly open the No. 1 piston is on the exhaust stroke.

Note: After the actual stroke position is identified, and the other stroke position is needed, remove the timing bolt from the flywheel. The flywheel is turned 360 degrees in a counterclockwise direction. The timing bolt is reinstalled.

Electronic Injection Timing Troubleshooting

Electronic injection timing troubleshooting is required if the electronic injection timing is inconsistent. Electronic injection timing troubleshooting is required if the electronic injection timing will not calibrate correctly. When either of these conditions are present, refer to Electronic Troubleshooting, RENR1328, " C10/ C12 and 3406E ", "PC-32: Engine Timing Calibration".