D399, G399, D398, G398, D379, G379 ENGINES Caterpillar

The most likely causes for faulty fuel injection performance are:

1. Air in the fuel system.

2. Low fuel supply.

3. Water in the fuel.

4. Clogged fuel filters.

5. Insufficient fuel transfer pump pressure.

If these conditions are checked and corrected and the engine still does not perform properly, the fuel injection equipment should be checked.

Checking Fuel Injection Equipment

Before removing a fuel injection pump or valve for testing from an engine that is missing or puffing black smoke at the exhaust, a simple check can be made to determine which cylinder is causing the difficulty. With the engine running at a speed which makes the defect most pronounced, momentarily loosen the fuel line nut on the injection pump sufficiently to cut out the cylinder. Check each cylinder in the same manner. If one is found where loosening makes no difference in the irregular operation of the engine or causes puffing of black smoke at exhaust to cease, probably the pump and valve, for only that cylinder, need be tested.

Fuel Injection Valve

The function of the fuel injection valve is to inject and atomize the fuel from the fuel injection pumps into the precombustion chambers. Irregular engine operation and smoking may be caused by an improperly operating injection valve.

The fuel injection valve is installed in the precombustion chamber.

The fuel injection valve assembly consists of the body (3), nut (2), and the capsule-type nozzle assembly (4).

Only the nozzle assembly need be replaced.

The nozzle assembly (4) and body (3) are held in place by the nut (2), and they can be removed by disconnecting the fuel line assembly (1) and removing the nut and seal.

The body and the nozzle assembly can then be lifted out. The nozzle assembly is only finger-tight on the body.

When installing a fuel injection valve, always check the seats of both the nozzle and the precombustion chamber.

FUEL INJECTION VALVE CROSS-SECTION
1-Fuel line assembly. 2-Nut. 3-Body. 4-Nozzle assembly.

Tighten the nut (2) to the torque of 100-110 lb. ft. (13,8-15,2 mkg). Excessive tightness will damage the nozzle. Excessive looseness will allow the nozzle to leak and in some instances cause the nozzle case to bulge or split.

Checking Fuel Injection Valves

The condition of a capsule type nozzle assembly can be tested out of the engine on the Caterpillar Diesel Fuel Injection Test Apparatus. The spray characteristic, valve unseating pressure, and the rate of leakage of the nozzle assembly can be determined.

Fuel Injection Pumps

Air in the fuel system is bled through the bleeder manifold (5) when the bleeder valve is opened and fuel enters the bleeder manifold through passage (7). The injection pump plungers (3) and the lifters (8) are lifted by cams on the camshaft (9) and always make a full stroke. Each pump (1) measures the amount of fuel to be injected into its respective cylinder and delivers it to the fuel injection valve. The amount of fuel pumped per stroke can be varied by turning the plunger in the barrel. The plunger is turned by the governor action through the rack (6) which meshes with the gear segment (4) on the bottom of the pump plunger.

FUEL INJECTION PUMP
1-Pump. 2-Inlet port. 3-Pump plunger. 4-Gear segment. 5-Bleeder manifold. 6-Rack. 7-Fuel passage. 8-Lifter. 9-Camshaft.

Figures A, B and C illustrate the functioning of an injection pump as the plunger makes a stroke.

In Fig. A the plunger is down and the inlet port (2) is uncovered. Fuel flows into the space above the plunger through the slot and into the recess around the plunger.

In Fig. B the plunger has started up and the port is covered. The fuel is trapped and will be forced through the check valve, fuel line and injection valve as the plunger moves upward.

In Fig. C the plunger has risen until the port is uncovered by the recess in the plunger. The fuel can now escape back through the port into the fuel manifold and injection will cease.

It will be noted that the recess in the pump plunger forms a helix around the upper end of the plunger. Figures D, E and F illustrate how rotating the pump plunger affects the quantity of fuel injected.

In Fig. D the plunger has been rotated into the shut-off position. The slot connecting the top of the plunger with the recess is in line with the port; therefore, no fuel can be trapped and injected.

In Fig. E the plunger has been rotated into the idling position. The narrow part of the plunger formed by the helix will cover the port for only a short part of the stroke. This permits anly a small amount of the fuel to be injected per stroke.

In Fig. F the plunger has been rotated into the full load position. The wide part of the plunger formed by the helix covers the port for a longer part of the stroke. This permits a larger amount of fuel to be injected per stroke.

Worn fuel injection pumps will result in loss of power and hard starting. These same conditions may be present if the piston rings and cylinder liners are badly worn. However, in the case of worn piston rings and liners, the hard starting and loss of power will be accompanied by poor compression, a smoky exhaust and excessive blow-by gasses from the crankcase breather.

Ordinarily, if one fuel injection pump on an engine is worn, it will be found that all of the injection pumps are worn and need replacing.

Failure to replace all of the worn injection pumps may result in erratic and irregular engine operation.

Removing Fuel Injection Pumps

When removing or installing the fuel injection pumps, every precaution should be taken to prevent dirt from getting in or around them.

1. Remove the fuel injection line from the pump and immediately cap and plug openings with cover (1) and plug (3).

REMOVING FUEL INJECTION PUMP
1-Cover. 2-Plug. 3-Fuel line plug. 4-Ferrule cap seal.

2. Remove bolts and clamps that hold the fuel injection pump body to the housing and lift the pump straight up to clear the dowel pins and the pump plunger. Place ferrule cap seals (4) over the fuel outlets and the plug (2) in the inlets to protect them from dirt.

3. Slide the end of the plunger out of the yoke in the lifter and lift out the plunger. Take every precaution to avoid nicking, scratching or getting dirt on the pump plunger, since the slightest rough spot or dirt will cause wear of the barrel and shorten the life of the pump. Be sure the plunger is replaced in the barrel from which it was withdrawn.

Installing Fuel Injection Pumps

The fuel injection pumps have a seal under the machined surface, around the large diameter of the pump. This seal must be positioned properly when the pump is being installed. Also, there must be a seal around the fuel outlet ferrule on the fuel pump housing. If either seal is damaged replace it.

1. Remove the pump plunger from the barrel.

2. Wash the pump plunger and barrel with clean diesel fuel before installing the barrel.

3. Turn the pump plunger, until the marked tooth (6) of the gear aligns with pump rack mark (5).

4. Slide the end of the plunger into the yoke in the lifter.

INSTALLING FUEL INJECTION PUMP
5-Mark on rack. 6-Marked gear tooth.

5. Lower the pump barrel onto the plunger taking care that the pump plunger does not become cocked in the barrel.

6. Lower the pump onto the dowel pins and fasten in place.

Fuel Injection Pump Housing

Removal and Installation

1. Remove the fuel pump and governor drive housing from the engine. See the topic, FUEL PUMP AND GOVERNOR DRIVE REMOVAL.

2. Remove the governor. See the covering topic.

3. Remove the bolts which hold fuel injection pump housing (2) to fuel pump and governor drive housing (1) and separate the housings.

4. Install in the reverse order of removal, replacing any damaged seals or gaskets.

FUEL INJECTION PUMP HOUSING REMOVAL (All D399 and Later D398 and D379 Engines Illustrated)
1-Fuel pump and governor drive housing. 2-Fuel injection pump housing.

FUEL INJECTION PUMP HOUSING REMOVAL (Earlier D398 and D379 Engines Illustrated)
1-Fuel pump and governor drive housing. 2-Fuel injection pump housing.

NOTE: It is necessary to time the fuel injection pump camshaft to the engine crankshaft when either the fuel injection pump housing or the fuel injection pump and governor drive housing has been removed. See the topic TIMING THE FUEL INJECTION PUMP CAMSHAFT.

Disassembly and Assembly

FUEL RACK REMOVAL (Earlier D398 and D379 Engines Illustrated)
1-Fuel rack.

REMOVING LIFTER YOKES AND RAISING LIFTERS
A-Lifter yoke. B-Locknut. C-Bolt. D-Washer. E-Threaded end of lifter.

THRUST PLATE REMOVAL
2-Bolts and locks. 3-Thrust plate.

1. Remove all the fuel injection pumps.

2. Remove fuel rack (1). The rack must slide freely in its bearings.

3. Loosen the locknuts (B) and remove the lifter yokes (A).

4. Install bolts (C) through washers (D) and into threaded ends (E) of the lifters. Use 6F7031 Bolts (3/8" - 24 NF thread, 3" long) and 4F3714 Washers.

5. Screw the bolts into the lifters far enough to raise the lifters free from the camshaft.

6. Remove camshaft (4), taking care not to damage the camshaft bearings.

REMOVING CAMSHAFT
4-Camshaft.

NOTE: Fuel injection pump camshafts have an arrow and an F-mark stamped on one end. For SAE standard rotation engines, the camshaft is installed with the arrow and the F-mark at the front of the fuel injection pump housing as shown. For SAE opposite rotation of the engine, the camshaft is turned end for end and installed with the arrow and the F-mark at the rear of the fuel injection pump housing.

FUEL INJECTION CAMSHAFT MARKS (Front View)
4-Camshaft.

7. Remove the bolt from the fuel pump lifter (6) and remove the lifter and spring (5) from the bottom of the housing.

LIFTER AND SPRING REMOVAL
5-Spring. 6-Fuel pump lifter.

8. Inspect camshaft bearings (7) and the fuel rack bearings and replace if necessary. When the clearance between the camshaft and bearings exceeds .006 in. (0.15 mm), replacement of the bearings or camshaft, or both, is necessary to insure proper operation.

CAMSHAFT BEARINGS
7-Bearings.

NOTE: Be sure to align the hole in the bearing with the oil hole in the fuel injection pump housing.

9. Assemble in the reverse order of disassembly.

10. Before installation of the fuel injection pump housing, adjust the lifter settings. See the topic, FUEL PUMP LIFTER SETTING (OFF ENGINE).

Checking Fuel Injection Pump Timing - On Engine

Checking With 1P540 Flow Checking Tool Group, 3S2954 Timing Indicator Group and 9M9268 or 9S215 Dial Indicator

Refer to Special Instruction (FM035709) for complete and detailed instructions for the fuel flow method of engine timing.

MEASURING PISTON TRAVEL
1-3S3263 Adapter. 2-9M9268 or 9S215 Dial indicator. 3-3S3264 Rod. 4-Precombustion chamber. 5-Inlet port. 6-Piston. 7-Crankshaft.

Travel of piston (6), from point of closing inlet port (5) to top center, can be found by using the 3S2954 Timing Indicator Group. Convert the travel of piston (6) into degrees to determine if engine timing is correct.

The 1P540 Flow Checking Tool Group is used to pressurize the fuel system. Maintain 10-15 PSI (0,70-1,05 kg/cm²) fuel pressure with the 1P539 Tank Assembly. This can be done with hand pump provided with the tank assembly, or connecting shop air to the tank assembly. If shop air is used, adjust the regulator to 15 PSI (1,05 kg/cm²).

Consult chart to find angle corresponding to indicator reading. At the indicator reading and timing angle specified for this particular engine, fuel flow from the injection pump should be reduced to 6-12 drops per minute [point of closing inlet port (5)].

If the proper indicator reading is not obtained, the fuel injection pump camshaft may require timing. See the topic, TIMING FUEL INJECTION PUMP CAMSHAFT. Several cylinders can be checked, and if variations in the readings exist, remove the fuel pump housing so all lifter settings can be checked and adjusted. See the topic, FUEL PUMP LIFTER SETTING (OFF ENGINE).

Checking With 6F6922 Micrometer Depth Gauge

TIMING MARKS ON FLYWHEEL (D399 Engine Illustrated)
1-Pointer.

1. Remove the timing mark cover on the flywheel housing and the injection pump of the respective lifter to be set.

2. Turn the crankshaft in the direction of engine rotation until pointer (1) aligns with the flywheel mark indicating piston TC (top center) on the compression stroke of the No. 1 piston.

TIMING MARKS ON FLYWHEEL (D398 and D379 Engines Illustrated)
1-Pointer.

NOTE: If the flywheel is turned too far, turn it back about 60° and again bring it up to TC (top center) mark. This procedure eliminates error which might otherwise occur because of backlash in the timing gears. The fuel pumps are numbered consecutively from front to rear.

3. Check the pump lifter setting when at this position with the 6F6922 Micrometer Depth Gauge.

MEASURING LIFTER SETTING DIMENSION (Typical Illustration)
2-Distance to be measured.

The reading should agree with the "ON ENGINE" lifter setting dimension of 2.076-2.080 in. (52,73-52,83 mm) for D399 Engines and 2.088-2.092 in. (53,04-53,14 mm) for D398 and D379 Engines.

If the proper reading is not obtained, the fuel injection pump camshaft may require timing. See the topic, TIMING FUEL INJECTION PUMP CAMSHAFT. Several cylinders can be checked, and if variations in the readings exist, remove the fuel pump housing so all lifter settings can be checked and adjusted. See the topic, FUEL PUMP LIFTER SETTING (OFF ENGINE).

Fuel Pump Lifter Setting (Off Engine)

The following procedure is for checking the lifters with the pump housing off the engine.

TOOLS REQUIRED FOR ADJUSTING LIFTERS OFF ENGINE
1-1F8747 Timing Plate. 2-6F6922 Micrometer Depth Gauge. 3-8M9018 Shaft. 4-3F1417 Washer. 5-No. 9 Woodruff Key. 6-8M9015 Adapter. 7-L1351 Bolt. 9-9M4568 Lifter Adjusting Wrench. 9-9M4567 Lifter Adjusting Wrench.

The tools shown are all the tools necessary for adjusting the lifters off the engine.

1. Attach timing plate (1) to the rear of the camshaft using shaft (3), key (5), bolt (7) and washer (4). Align the key in shaft (3) with the slot in the camshaft. This positions the timing plate in relation to the camshaft and allows the camshaft to be rotated by the timing plate.

2. Place adapter (6) over the dowel in the end of the pump housing and bolt it in place.

3. Refer to the table and select the appropriate timing plate setting for the lifter being checked or set. Set the timing plate to this setting by rotating the plate, in the same direction as the arrow on the end of the camshaft indicates, until the proper degree setting lines up with the inside edge of the boss (11) on adapter assembly (6). Lock in position with lockscrew (10).

FUEL PUMP LIFTER SETTING OFF ENGINE
1-1F8747 Timing Plate. 2-6F6922 Micrometer Depth Gauge. 6-8M9015 Adapter. 10-Lockscrew. 11-Edge of boss. A-Dimension to be measured.

4. Use depth gauge (2) to check the fuel pump lifter setting (dimension A). This dimension is the distance from the flat surface on the top of the housing to the plunger seating surface in the yoke of the lifter being set. If necessary, use a 9M4568 Wrench (8) and a 9M4567 Wrench (9) to adjust dimension (A) to "OFF ENGINE" lifter setting dimension of 2.156-2.157 in. (54,76-54,79 mm) for all engines.

NOTE: To get an accurate depth gauge reading, be sure the flat surface on top of the fuel pump housing is clean, dry and free of paint.

5. If all the lifters are to be checked or reset, continue the same procedure in the firing order of the engine. See the chart for firing order. Recheck each lifter setting after the adjustment has been made and the locknut tightened to make sure the setting has not changed.

Fuel injection pumps are numbered consecutively from front to rear on all of these engines.

Fuel Pump Lifter Yoke And Pump Plunger Inspection

Adjusting the fuel pump lifters is necessary whenever they have been removed from the housing. The adjustment should also be checked to compensate for wear in the lifter yokes to assure that the point of fuel injection is correct. If the lifter is too high, injection will begin early, and, if too low, injection will be late.

When pump plunger wear becomes excessive, the lifter yoke may also be worn in such a manner that it will not make full contact with the end of a new plunger. To avoid rapid wear on the end of the new plunger, lifter yokes showing visible wear should always be replaced.

WEAR BETWEEN YOKE AND PLUNGER

Fig. A illustrates the contact surfaces of a new pump plunger and a new lifter yoke. In Fig. B, the pump plunger and lifter yoke have worn considerably. Fig. C shows how the flat end of a new plunger makes poor contact with a worn lifter yoke, resulting in rapid wear to both parts.

A pump can maintain a satisfactory discharge rate and yet be unserviceable because of delayed timing resulting from wear on the lower end of the plunger. When testing a pump which has been in use for a long time, the length of the plunger should be checked with a micrometer. The length of new plungers is 2.9831-2.9837 in. (75,771-75,786 mm). The minimum permissible worn plunger length is 2.9781 in. (75,644 mm).

Timing The Fuel Injection Pump Camshaft

Introduction

FUEL PUMP AND GOVERNOR DRIVE
A-Fuel pump and governor drive gear. B-Governor drive pinion cage assembly. C-Governor. D-Fuel injection pump housing. E-Tachometer drive gear. F-Fuel pump and governor drive shaft. G-Coupling. H-Fuel injection pump camshaft.

Timing

It is necessary to time the fuel injection pump camshaft to the engine crankshaft whenever the pump housing or injection pump drive has been removed.

1. Remove the timing mark cover on the flywheel housing and turn the flywheel in the direction of engine rotation until No. 1 piston is at TC (top center) on compression as indicated by flywheel pointer (1).

TIMING MARKS ON FLYWHEEL (D399 Engine Illustrated)
1-Pointer.

TIMING MARKS ON FLYWHEEL (d398 and D379 Engines Illustrated)
1-Pointer.

NOTE: If the flywheel is turned too far, turn it back about 60° and again rotate the flywheel in the direction of normal rotation until No. 1 piston is at TC (top center) on compression as indicated by the flywheel pointer.

CAMSHAFT GEAR ASSEMBLY
2-Gear. 3-Plate. 4-Puller bolt. 5-Shaft. 6-Lock. 7-Collar.

2. The fuel pump and governor drive gear (2) has a puller built-in to the puller bolt (4). This puller bolt is used to loosen the gear from the drive shaft.

NOTE: The puller consists of puller bolt (4), lock (6), collar (7) and plate (3). The puller bolt is retained in the plate by collar (7) welded to the bolt. The plate is bolted to gear (2). When the puller bolt is turned counterclockwise, the force of collar (7) against the plate pulls the gear from shaft (5). When the bolt is turned clockwise, the gear is forced on the tapered shaft by the plate.

3. Remove the plug from the top of the flywheel housing. Pull the governor and fuel pump drive camshaft gear from the shaft. Two 1/2" drive wrench extensions (8) can be used to turn the puller bolt. Lock (6) can be spread with a screwdriver.

PULLING THE GOVERNOR AND FUEL PUMP DRIVE CAMSHAFT GEAR (Aftercooler Removed For Better Illustration)
8-Wrench extensions.

TIMING THE FUEL INJECTION PUMP
9-Lifting eye. 10-Ratchet wrench handle. 11-Breather cavity.

4. Remove lifting eye (9) and the fuel inlet flange.

5. Remove the breather in front of the fuel injection pump housing.

6. Insert the lifting eye (which is also a timing pin) into the hole from which it was removed with fuel inlet flange removed. Do not tighten at this time.

7. Through breather cavity (11), rotate the fuel pump camshaft until timing slot (12) is on top. Screw the lifting eye into the timing slot as illustrated.

TIMING PIN LOCATED IN TIMING SLOT (Pump Housing Removed For Clearer Illustration)
9-Lifting eye. 12-Timing slot.

8. With the lifting eye in place, tighten the camshaft gear puller bolt and force the gear onto the shaft. Tighten puller bolt to torque of 265 ± 35 lb. ft. (36,6±4,8 mkg). Bend lock (6) into place on the bolt.

9. Remove the lifting eye. The fuel injection pump camshaft is in time.

NOTE: A fuel pump camshaft rotating tool, 9S6054 Socket, can be used with ratchet wrench handle (10) to rotate the fuel pump camshaft accurately.