Cleaning 3600 Unit Injectors{1290} Caterpillar

Introduction

This Special Instruction provides the necessary information required to disassemble, clean, inspect, and assemble unit injectors for 3600 Engines.

This Special Instruction also includes the dimensions and recommended material for fabricating specialized tooling.

NOTE: This Special Instruction should be read and understood before proceeding with any disassembly, cleaning, inspection, or assembly.

Unit Injector Components Are Not Serviced

NOTE: The component parts in unit injectors used for 3600 Engines are NOT serviced.

The unit injectors will be OUT of calibration if components are interchanged within the unit injectors.

If during the cleaning and inspection procedure a component is found to be excessively worn, the complete unit injector must be REPLACED.

Factory Adjustment ONLY

NOTE: A trim bolt (Allen head design) is provided on the unit injectors to adjust the rack zero point at the factory ONLY.

The ALLEN HEAD trim bolt should NOT be moved, adjusted, or tightened.

There have been instances where the bolt has been mistaken for a fastener rather than an adjustment.

Work Area Environment And Component Cleaning Procedures

The cleanliness of the parts and the work area during this repair procedure is VERY important.

The cleaning procedure should be performed in an air-conditioned area to provide humidity control and isolation from contamination in the air.

Work surfaces of stainless steel are best.

Do NOT use work benches with painted surfaces or those made of materials that are difficult to keep clean.

If non-metallic materials are to be used for the work bench tops, the material must be resistant to chipping and scratching, and not affected by diesel fuel, test fluid, or caustic solutions.

Recommended Tools

NOTE: The use of some of the following tools (Ultrasonic Cleaner and Test Fluid) depends on the type of cleaning. Read this Special Instruction before ordering.

Fabricated Specialized Tooling

Sleeve (Tool A)

Illustration 1: (A) 100 mm (4.0 in). (B) 77.22 ± 0.05 mm (3.040 ± .002 in). (C) 75 mm (3.0 in). (D) 54.8 mm (2.16 in). (E) 3 mm (.1 in). (F) 82.68 ± 0.05 mm (3.255 ± .002 in). (G) 1.5 mm (.06 in) × 45 degrees. (H) 30 degrees.

Material

Fabricate from aluminum or plastic.

Pedestal (Tool B)

Illustration 2: (A) 178 mm (7.0 in). (B) 89 mm (3.5 in). (C) 89 mm (3.5 in). (D) 70 mm (2.8 in). (E) 89 mm (3.5 in). (F) 152 mm (6.0 in). (G) 6.4 mm (.25 in). (H) Dowel - 19 mm (.7 in) diameter × 38 mm (1.5 in). (I) 12.7 mm (.50 in). (J) 304.8 mm (12.00 in). (K) 330 mm (13.0 in). (L) Weld.

Material

Fabricate from mild steel.

Compression Plate (Tool C)

Illustration 3: (A) 100 mm (4.0 in). (B) 50 mm (2.0 in). (C) 24.25 ± 0.50 mm (.955 ± .020 in). (D) 42.0 ± 0.5 mm (1.65 ± .02 in). (E) 9.5 mm (.37 in) two holes. (F) 3 mm (.1 in) × 45 degrees. (G) 12.0 mm (.47 in). (H) 7.0 ± 0.2 mm (.28 ± .01 in). (I) 74.0 ± 0.2 mm (2.91 ± .01 in). (J) 57.15 ± 0.20 mm (2.250 ± .008 in).

Material

Fabricate from mild steel.

Timing Mark Indicator (Tool D)

Illustration 4: (A) 25 mm (1.04 in). (B) 12.95 ± 0.25 mm (.510 ± .010 in). (C) 6.35 mm (.250 in). (D) 1.5 mm (.06 in). (E) 15.75 mm (.620 in). (F) 25 mm (1.0 in). (G) 42 mm (1.7 in).

Material

Fabricate from mild steel.

Unit Injector Parts

Illustration 5: (1) Case. (2) Unit injector body. (3) Tappet spring. (4) Tip assembly (part of check assembly). (5) Check (part of check assembly). (6) Stop (part of check assembly). (7) Sleeve (part of check assembly). (8) Spill deflector. (9) Spring (check). (10) Plate. (11) Barrel (part of plunger assembly). (12) Injector plunger (part of plunger assembly). (13) Plunger gear (part of plunger assembly). (14) Retainer. (15) Rack. (16) Tappet retainer pin. (17) Keeper. (18) Tappet assembly.

In this cleaning procedure, only the tappet spring, tappet assembly, and plunger will be disassembled from the unit injector. Component parts are NOT interchangeable.

Cleaning, Handling And Storing Of Unit Injector Parts

Cleaning

A unit injector is made of close tolerance with precision parts that can be damaged by rust, foreign material, or careless handling.

Cleaning should be made in an environment that is clean and of low humidity.

Skin or finger contact with the precision surfaces of the plunger and barrel should be avoided because body fluids and salt can cause corrosion.

Handling

If it is necessary to touch these precision surfaces, always use clean hands that have been wet with clean test fluid.

Do NOT let any of the parts remain dry for long periods of time, ESPECIALLY after cleaning. To prevent corrosion, thoroughly wet each part with clean test fluid during the cleaning process.

Storage

The assembled unit injector must have adequate protection against rust, dirt, and mechanical damage during storage.

Clean 6V-6067 or 6V-6068 Test Fluid or equivalent test fluid that meets SAE 967 or ISO4113 Standards provides good protection for the internal parts if they are well coated and not allowed to dry.

The exterior of the unit injector may be coated with clean test fluid or a protective oil.

The unit injectors should be packaged and stored in containers that keep out dirt and moisture, and prevent mechanical damage to the unit injectors.

The parts of the unit injector that are the most vulnerable to mechanical damage are the tip and the rack.

Unit Injector Cleaning And Disassembly

(A) Sleeve (Tool A).

1. Clean the outer surface of the unit injector before it is disassembled. Install sleeve tool (A) on each unit injector, to cover the unit injector fuel ports.

Unit injectors can be cleaned as shown, or they can be placed in an agitator-type solvent tank.

(1) 8S-2258 Brush.

2. For those unit injectors that have an excessive amount of carbon, use an 8S-2258 Brush (1) to remove carbon from the unit injector tip.

NOTE: Do not use a power brush or any brush with steel bristles to perform the cleaning procedure. Use only a brush that has brass bristles.

(B) Pedestal (Tool B).

3. Place unit injector in Pedestal (Tool B).

Illustration 6: (15) Rack.

The control arm connection block on rack (15) should be to the left.

Illustration 7: (1) Case. (2) Unit injector body. (3) Tappet spring. (4) Tip assembly (part of check assembly). (5) Check (part of check assembly). (6) Stop (part of check assembly). (7) Sleeve (part of check assembly). (8) Spill deflector. (9) Spring (check). (10) Plate. (11) Barrel (part of plunger assembly). (12) Injector plunger (part of plunger assembly). (13) Plunger gear (part of plunger assembly). (14) Retainer. (15) Rack. (16) Tappet retainer pin. (17) Keeper. (18) Tappet assembly.

A slot in unit injector body (2) and tappet retainer pin (16) should be visible behind tappet spring (3).

4. Install two 5/16-18 × 230 mm (9.1 in) threaded rods in the unit injector body (2).

Center the compression plate (Tool C) over the unit injector and threaded rods.

Install 5/16-18 nuts and washers on the threaded rods. The threaded rods should project 20.0 mm (.79 in) beyond the nuts. This will provide thread length to relax tappet spring (3).

5. Turn nuts down evenly on both sides while holding tappet assembly (18) in the up position as tappet spring (3) is being compressed.

Hold tappet assembly (18) in the up position with a suitable tool placed through the spring coils and under the tappet retainer pin (16).

6. Remove keepers (17) and carefully loosen compression plate (Tool C). The tappet assembly should only move as far as tappet retainer pin (16) allows.

Remove the nuts from the threaded rods and remove compression plate (Tool C).

NOTE: The nuts and compression plate (Tool C) must be removed before the retainer and spring can be removed.

7. Before removing the tappet assembly and plunger, install the timing mark indicator (Tool D) between the control arm connection block on rack (15) and unit injector body (2).

Ensure a timing mark on plunger gear (13) is visible through the slot in the unit injector body.

The tappet assembly will have to be held in the up position in order for the timing mark to be seen.

If no timing mark is visible, an indelible mark should be placed on a visible gear tooth with timing mark indicator (Tool D) in place.

NOTE: It is very important that the gear on injector plunger (12) and rack (15) be timed exactly when reassembled.

8. With timing mark indicator (Tool D) in place, use a small screwdriver or other similar tool to push in tappet retainer pin (16). This will permit separation of the tappet assembly from the unit injector body.

NOTE: On earlier unit injectors it may be necessary to remove an Allen head bolt located in the slot of unit injector body (2).

Carefully lift tappet assembly (18) and injector plunger (12) from the unit injector.

9. Slide injection plunger (12) from tappet assembly (18).

NOTE: Some specific parts of a unit injector, such as the plunger and barrel, are a mated fit (machined as a set). These parts must NOT be used SEPARATELY with any other plunger and barrel. The plunger assembly and the tip assembly are matched to each other to obtain correct fuel flow. Always keep these parts together.

10. Place keeper (17), tappet spring (3), and tappet assembly (18) in another container for cleaning.

These parts can be cleaned like other engine parts in a solvent tank or hot tank, or in an ultrasonic cleaning tank, using the basket that comes with the tank.

11. Remove the timing mark indicator (Tool D) and rack (15) from the unit injector body.

Cleaning Procedure After Disassembly

Cleaning unit injectors consist mainly of removing deposits of carbon and varnish.

Always be careful when handling plungers to prevent damage.

Always keep mated and matched parts together during the cleaning procedure.

Mated parts are machined to fit each other and can NOT be used with other parts.

Matched parts have been selected to be used together to get the correct fuel flow, and should be kept together during the cleaning and assembly procedure.

Hand Cleaning Method For Plungers

Cleaning the plungers with clean 6V-6067 or 6V-6068 Test Fluid or equivalent test fluid that meets SAE967 or ISO4113 standards and using a 6V-7093 Brush Assembly is an effective method for removing carbon and varnish from the plungers.

Ultrasonic Cleaning Method For Plungers

Ultrasonic cleaning is fast, effective, and convenient for cleaning most plungers.

Cleaning time is usually fifteen to thirty minutes, with thirty minutes being the maximum for even the dirtiest unit injector parts.

Use 6V-6050 Ultrasonic Cleaner for 110 Volt 60 Hz or 6V-6060 Ultrasonic Cleaner for 230 Volt 50 Hz.

NOTE: Each plunger and barrel are a mated fit. To ensure that mated parts are kept together, REMOVE and INSPECT ONLY ONE plunger at a time.

Inspection Of Plunger

Illustration 8: (12) Injection plunger. (13) Plunger gear. (G) Location. (H) Location.

1. Inspect injection plunger (12), especially at scroll location (G).

Any scratches, rust, or erosion (uneven wear) at location (G) can be an indication that the unit injector will not pump the correct amount of fuel.

If a scratch, rust, etc. at location (G) can be felt with your fingernail, the plunger is worn too much and the unit injector should be replaced.

2. Some surface conditions to look for at location (G) are:

SCRATCHES: Scratches are caused by dirt in the fuel or other foreign material that get into the unit injector.

RUST DAMAGE: Rust damage that is caused either by water in the fuel, or by incorrect storage procedures for unit injectors.

CAVITATION EROSION: The surface condition of the plunger, especially in the area of location (G), will look and feel similar to emery cloth.

This condition is normally seen in a unit injector that has high operating hours, and is caused by the constant impact of high velocity fuel as it strikes the surface of the plunger.

3. Surface defects away from the scroll area are less likely to affect fuel delivery but can cause sticking or seizure of the plunger.

NOTE: Any condition that causes the plunger to stick or bind is NOT acceptable.

Place the plunger in clean test fluid to ensure good lubrication before checking the plunger movement.

If the plunger still sticks, the unit injector should be replaced.

NOTE: A plunger can look satisfactory and not stick; but still be worn too much to deliver the correct amount of fuel. It may also leak. Usually, if a plunger looks good and feels good, it probably is in good condition.

4. It is normal for plunger gear (13) to have wear mark(s) or polished area(s) on the gear teeth at [location (H)] that is caused by contact with rack (15).

If the wear marks at each location (H) can be felt with the point of a pencil, or if the teeth are worn to a sharp edge, the gear is worn too much.

Cleaning Of Unit Injector Barrel

Illustration 9: (1) Case. (2) Unit injector body. (3) Tappet spring. (4) Tip assembly (part of check assembly). (5) Check (part of check assembly). (6) Stop (part of check assembly). (7) Sleeve (part of check assembly). (8) Spill deflector. (9) Spring (check). (10) Plate. (11) Barrel (part of plunger assembly). (12) Injector plunger (part of plunger assembly). (13) Plunger gear (part of plunger assembly). (14) Retainer. (15) Rack. (16) Tappet retainer pin. (17) Keeper. (18) Tappet assembly.

1. Place a unit injector body in Pedestal (Tool B) with the tip up.

This will allow cleaning fluid to drain from barrel (11).

2. Flush barrel (11) with cleaning solution filtered to the 5 micron level.

Use clean 6V-6067 or 6V-6068 Test Fluid or equivalent test fluid that meets SAE967 or ISO4113 Standards as a cleaning solution.

A 6V-7093 Brush Assembly can be used to remove varnish deposits.

Do NOT remove barrel (11) from the unit injector.

NOTE: The barrel can NOT be removed from the unit injector without complete disassembly.

Complete disassembly is NOT recommended because doing so will require factory calibration.

Inspection Of Rack

Illustration 10: (15) Plunger rack. (M) Location. (N) Location.

Illustration 11: (1) Case. (2) Unit injector body. (3) Tappet spring. (4) Tip assembly (part of check assembly). (5) Check (part of check assembly). (6) Stop (part of check assembly). (7) Sleeve (part of check assembly). (8) Spill deflector. (9) Spring (check). (10) Plate. (11) Barrel (part of plunger assembly). (12) Injector plunger (part of plunger assembly). (13) Plunger gear (part of plunger assembly). (14) Retainer. (15) Rack. (16) Tappet retainer pin. (17) Keeper. (18) Tappet assembly.

1. Inspect plunger rack (15) for wear and to ensure it is straight.

Rack teeth at location (M) must be smooth.

Any wear marks that can be felt with a pencil point are an indication that the rack is worn too much and that the unit injector should be replaced.

2. Inspect the surface condition at both locations (N) on the collar.

If any wear marks at either location (N) can be felt with the finger, it is an indication that the rack is worn too much and the unit injector should be replaced.

3. Locations (N) on the collar must be parallel with each other. If the surfaces are NOT parallel, it is normally an indication that the rack collar is bent.

4. To check for a straight rack, install rack (5) in unit injector body (2). Rack (15) must slide in and out freely.

NOTE: The final check to see if the rack is straight will be made when the unit injector is completely assembled.

Inspection Of Injector Body And Case

Illustration 12: (P) Bore. (R) Slot. (S) Surface. (T) Location of case (1). (U) O-ring seal groove.

1. There must not be any nicks or burns in, or around, O-ring seal grooves (U) or on the taper at location (T) of case (1).

Use emery cloth to carefully remove any nicks or burns at either location.

2. Inspect unit injector body at bore (P), slot (R), and surface (S):

BORE (P) AND SLOT (R): Bore (P) and slot (R) must be smooth, free of burns, and permit free movement of the tappet.

SURFACE (S): Surface (S) is used in the timing procedure when the unit injector is installed in the engine.

This surface must be smooth and free of all nicks and burns.

Inspection Of Tappet Assembly

Illustration 13: (16) Tappet retainer pin. (18) Tappet assembly. (W) Location.

1. The area all around location (W) must be free of any nicks or burns that can prevent free movement of the tappet assembly (18) in the unit injector body.

2. Inspect tappet retainer pin (16) for damage and wear.

Ensure tappet retainer pin (16) is extended as far as possible in order to keep the tappet in the body when the unit injector is completely assembled.

Assembly Procedure

Illustration 14: (1) Case. (2) Unit injector body. (3) Tappet spring. (4) Tip assembly (part of check assembly). (5) Check (part of check assembly). (6) Stop (part of check assembly). (7) Sleeve (part of check assembly). (8) Spill deflector. (9) Spring (check). (10) Plate. (11) Barrel (part of plunger assembly). (12) Injector plunger (part of plunger assembly). (13) Plunger gear (part of plunger assembly). (14) Retainer. (15) Rack. (16) Tappet retainer pin. (17) Keeper. (18) Tappet assembly.

1. Slide rack (15) into a unit injector.

Place the unit injector in pedestal (Tool B) with the tip down.

Place timing mark indicator (Tool D) between the control arm connection block on rack (15) and unit injector body (2).

NOTE: The timing mark on the rack should be visible and centered in the tappet pin slot in the body.

2. Before installing the mated plunger (12), place the selected plunger (must be matched with the barrel in the unit injector) and follower (17) in clean test fluid.

Position the plunger in the tappet assembly.

3. Locate the timing mark on the gear on the plunger (12).

Carefully lower the assembly into the barrel while keeping the timing marks on the gear and rack aligned.

NOTE: The gear and plunger must be timed exactly or the unit injector will require calibration. Calibration is performed at the factory ONLY.

4. After the gear is engaged with rack (15), turn tappet assembly (18) to align tappet retainer pin (16) with slot in unit injector body (2).

5. While depressing tappet retainer pin (16) with the screwdriver, push the tappet assembly into the unit injector body.

The tappet assembly pin will start into the unit injector body.

The plunger and tappet assembly can easily be inserted into the unit injector.

6. Lower tappet spring (3) over unit injector body (2).

Install retainer (14).

Install two 5/16- 18 × 230 mm (9.1 in) threaded rods in the unit injector body.

Center compression plate (Tool C) over the unit injector and threaded rods.

Install 5/16- 18 nuts and washers on rods.

7. Turn nuts down evenly on both sides while holding tappet assembly (18) in the up position as tappet spring (3) is being compressed.

Hold tappet assembly (18) in the up position with a suitable tool placed through the spring coils and under the tappet retainer pin (16).

8. Install keepers (17) and carefully loosen compression plate (Tool C).

Remove nuts, washers, and threaded rods.

9. After the unit injector has been completely assembled, remove the unit injector from the fixture.

Pivot the unit injector to check for free travel of the rack.

Lift the rack to its full up position, and let it fall.

The rack must fall freely.

10. The rack will not fall due its own weight. Place 6V-4809 Rack Weight Cup over the rack collar.

If the rack falls with the rack weight cup installed but with no additional force, rack freedom is acceptable.