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

Introduction

A combined overspeed and low oil pressure safety shutoff is provided for industrial engines, but is available as an attachment on earlier marine engines.

Later D398 and D399 Marine Engines are equipped with reversal protection in addition to overspeed. The reversal protection safety shutoff is available as an attachment for D379 Marine Engines.

The safety shutoff (1) is mounted in the V of the engine at the rear of the governor housing with the control driven from the fuel pump and governor drive shaft.

Engine lubricating oil pressure is used to actuate the low oil pressure shutoff control portion. The plug (2) provides for a connection of oil pressure to a water temperature shutoff control valve. The line (4) supplies engine oil pressure to the shutoff control.

SAFETY SHUTOFF CONTROL
1. Safety shutoff control. 2. Plug (pressure oil connection to water temperature shutoff). 3. Fuel rack shutoff. 4. Pressure oil line to shutoff control. 5. Reset button. 6. Emergency manual shutoff button.

The overspeed shutoff portion of the control stops the engine mechanically in the event of engine overspeeding.

Controls equipped with reversal protection are activated by low oil pressure in the event the engine runs in reverse.

The emergency manual shutoff button (6) works in conjunction with the overspeed shutoff and provides the operator with an emergency shutoff.

Reset button (5) is used to reset the control after the engine has been stopped by the control because of low oil pressure or high water temperature.

NOTE: It is not necessary to reset the control after a normal engine stopping.

The shutoff mechanisms receive lubricating oil from leakage past the oil pressure shutoff piston. An internal drain is provided by two drilled holes in the bottom of the housing.

Operation

Low Oil Pressure Shutoff and Water Temperature Shutoff

The oil pressure control will stop the engine should the lubricating oil pressure drop below the safe operating range, or when excessively hot water opens a shutoff control valve which simulates low oil pressure.

Under normal engine operating conditions, engine lubricating oil is directed through supply line (4), see previous illustration, to cover (4). This oil is then directed against control piston (6).

One end of worm slide follower (2) is piloted into guide (5). The follower is free to pivot about slide follower shaft (3) in the housing and is actuated by the movement of guide (5).

SHUTOFF CONTROL (Cross Sectional Side View; Normal Operation)
1. Worm shaft. 2. Slide follower. 3. Slide follower shaft. 4. Cover. 5. Guide. 6. Piston. 7. Spring. 8. Release rod.

Worm shaft (1) is driven by the safety shutoff drive which is driven by the fuel pump and governor drive shaft thus rotating any time the engine is operating.

When the engine oil pressure is within the safe operating range, the piston (6) is held against the guide (5) compressing the spring (7) and pivoting the slide follower (2) out of mesh with the worm shaft (1).

Should the lubricating oil pressure drop below normal operating range, the oil pressure acting on piston (6) will also drop and spring (7) will force guide (5) and piston (6) to the stop position and cause slide follower (2) to pivot on shaft (3) and mesh with worm shaft (1).

SHUTOFF CONTROL (Top View; Normal Operation Position)
1. Worm shaft. 2. Slide follower. 3. Slide follower shaft. 5. Guide. 8. Release rod. 9. Pin. 10. Release lever. 11. Spring.

With slide follower (2) engaged with worm shaft (1), the slide follower will travel the length of worm portion of shaft (1). As the follower comes close to the end of its travel, pin (9) on the follower makes contact with release lever (10). The release lever is then tripped and releases rod (8) which is forced outward by spring (11).

SHUTOFF CONTROL (Side View; Shutoff Operation Position)
1. Worm shaft. 2. Slide follower. 3. Slide follower shaft. 5. Guide. 6. Piston. 7. Spring. 8. Release rod.

Release rod (8) moves to contact spring-loaded plunger (12) in the rear of the governor drive housing. The plunger then moves forward contacting the lever assembly in the governor drive housing, moving it to the OFF position and stopping the engine.

SHUTOFF CONTROL (Top View; Shutoff Operation Position)
1. Worm shaft. 2. Slide follower. 8. Release rod. 9. Pin. 10. Release lever. 11. Spring.

RACK SHUTOFF
12. Plunger.

Overspeed Shutoff

Should an overspeeding condition occur, the overspeed shutoff control located in the shutoff control housing will actuate the release rod and then the fuel rack to OFF position to stop the engine.

Overspeed carrier assembly (1) is driven by gears and the safety shutoff drive which is driven by the fuel pump and governor drive shaft thus rotating whenever the the engine is operating. Within the carrier flange is a rotating weight (2) held toward the center of the carrier shaft by an adjusting screw, spring and nut.

OVERSPEED CONTROL
1. Carrier assembly. 2. Rotating weight. 3. Release lever. 4. Release rod.

As the engine rpm increases, the centrifugal force acting on the weight increases and the weight moves out of the carrier flange. This movement of the weight continues until the spring force (tending to hold the weight in) is equal to the centrifugal force (tending to throw the weight out).

When the engine overspeeds, the weight will continue to move out of the carrier flange until it makes contact with release lever (3) and releases release rod (4) which actuates the fuel shutoff linkage and stops the engine.

Emergency Manual Shutoff Button

The emergency shutoff button (5) is never used for normal shut-down. Under normal conditions all load would be first removed from the engine and the engine rpm lowered to low idle before the engine is shut off.

If an emergency situation is encountered where the engine should be shut down immediately, push the emergency shutoff button and hold in the button until the release rod has been released.

By pushing button (5), plunger (4) acts against pin (3) which forces spring-loaded weight (1) out of carrier assembly (2) creating the same condition as overspeeding.

EMERGENCY SHUTOFF
1. Weight. 2. Carrier assembly. 3. Pin. 4. Plunger. 5. Button.

Resetting The Control

Whenever the engine has been shut down by the safety shutoff control, the reason for the shutdown must be corrected and the control reset before the engine can be restarted.

Resetting After Overspeed and Emergency Manual Shut-down

The spring-loaded release rod is relatched by moving the reset lever (1). The engine can now be started.

SHUTOFF CONTROL RESET
1. Lever.

Resetting After Low Oil Pressure or Water Temperature Shut-down

Push reset button (4) on the top of the shutoff control housing. This manually moves the control piston (3) and pin against slide follower guide (1). The movement of the guide pivots worm slide follower (2) away from the end of the worm shaft and allows the spring to return the slide follower to the start of the worm shaft threads.

SHUTOFF CONTROL RESET
1. Slide follower guide. 2. Slide follower. 3. Piston. 4. Reset button. 5. Release rod.

Latch the spring-loaded release rod (5) by pulling on the reset lever. See the topic RESETTING AFTER OVERSPEED AND EMERGENCY MANUAL SHUT-DOWN.

The engine can now be started.

NOTE: In cold weather operation it my be necessary to push the reset button momentarily while cranking the diesel engine to prevent actuating the shutoff control. This is necessary as the oil pressure may not reach the operating range rapidly enough due to the longer cranking period usually encountered under these conditions.

Under normal operation conditions, lubricating oil pressure will reach the operating range before the follower has reached the limit of travel and actuates the release lever and rod.

Overspeed Control Adjustment

The overspeed control mechanism is adjusted at the factory and should not be changed unless the carrier assembly has been disassembled or the adjustment disturbed in some way. The overspeed control is originally set to shut down the engine if the engine rpm rises more than 18% above full load rpm.

Adjustment on Engine

The adjustment is made by removing the plug from the front of the shutoff housing to gain access to the weight adjusting screw. It may be necessary to rotate the flywheel until the adjusting screw can be reached with an offset screwdriver (1) as illustrated.

ADJUSTING THE WEIGHT SPRING TENSION
1. Offset screwdriver.

One complete turn of the adjusting screw will vary the maximum overspeed limit from 45 to 50 rpm. Clockwise rotation of the adjusting screw will compress the spring and raise the maximum speed limit, while counterclockwise rotation of the screw will allow the spring to expand and lower the maximum speed limit.

Bench Testing

On engine adjustment of the control may be impractical. The FT907 Adapter (C) with a reversible variable speed drill (D) and tachometer will allow a bench adjustment to be made.

1. Connect the 1P7443 or 4S6991 Tachometer) part of the 4S6553 Engine Test Box) to the tachometer drive on the safety shutoff control (A).

2. Use the FT907 Adapter and variable speed drill to drive the control as shown.

NOTE: If adjustment or check of the overspeed is made without depressing the oil pressure reset button, a low oil pressure activation can result.

3. Read the speed indicated on the 4S6991 Tachometer at the moment the safety control is activated. The reading indicates engine speed (2 rpm on the scale for each rpm the input shaft is turned).

TESTING OVERSPEED CONTROL
A. Safety control. B. 4S6553 Engine Test Box. C. FT907 Adapter. D. Reversible variable speed drill.

4. If necessary, turn the weight adjusting screw, reset the release rod and again test and adjust until the proper setting is made.

Safety Shutoff Control

Removal and Installation

Remove ball joint (1) and nut (2) and slide cable (3) free of the support bracket.

Remove the safety shutoff control (4) and cable (3) as a unit.

Inspect all parts for wear or damage and replace if necessary.

PREPARING TO REMOVE SAFETY SHUTOFF CONTROL
1. Ball joint. 2. Nut. 3. Cable.

PREPARING TO REMOVE SAFETY SHUTOFF CONTROL
3. Cable. 4. Safety shutoff control. 5. Oil line. 6. Bolts (five).

Reset Button and Piston Removal and Installation

REMOVING COVER ASSEMBLY
1. Bolts (three). 2. Tachometer drive housing assembly (when so equipped). 3. Cover assembly.

REMOVING PISTON
4. Piston.

Replace the mounting gasket if necessary.

Reset Button Disassembly and Assembly

Inspect the O-ring seal (3) and replace it if damaged.

RESET BUTTON DISASSEMBLY
1. Plunger. 2. Spring. 3. O-ring seal. 4. Pin.

Removal and Installation of Drive Assembly

DRIVE AND ADAPTER REMOVAL
1. Screw (two). 2. Adapter assembly. 3. Drive shaft.

The drive shaft (3) and adapter assembly (2) should be removed as a unit.

Disassembly and Assembly of Drive Assembly

NOTE: After removal, the gear assembly (2), consisting of two gears, one spacer, a bearing, and two dowel pins (8) can be disassembled by driving out the dowel pins.

Inspect all parts for wear or damage and replace any required.

DRIVE ASSEMBLY DISASSEMBLY
1. Adapter. 2. Gear assembly. 3. Washer. 4. Snap ring. 5. Dowel. 6. Shaft. 7. Gear. 8. Dowel pins (two). 9. Drive shaft.

Carrier and Weight Disassembly and Assembly

With the adapter and drive shaft removed, the carrier and weight assembly (1) can be removed from housing (2) and disassembled in the following manner:

1. Using 8H695 Puller and 8B7560 Step Plate, remove gear (5) and replace it if worn or damaged.

2. Clean up the staked area around screw (6) and remove the screw from carrier (4).

CARRIER AND WEIGHT REMOVAL
1. Carrier and weight assembly. 2. Housing.

NOTE: The screw (6) is both a guide for the weight and a safety device to keep the weight from flying out should the bolt (3) break for any reason.

CARRIER DISASSEMBLY
3. Screw. 4. Carrier. 5. Gear. 6. Screw. 7. Weight.

NOTE: When removing screw (3), count the number of turns required to remove. When installing the screw, install with the same number of turns. For correct adjustment after assembly, see the topic, OVERSPEED CONTROL ADJUSTMENT.

3. Remove screw (3), nut (10), spring (8), weight (7) and pin (9) from carrier (4).

CARRIER DISASSEMBLY
3. Screw. 7. Weight. 8. Spring. 9. Pin. 10. Nut.

4. Assemble in reverse order of disassembly, restaking the area around the screw (6).

Emergency Shutoff Button Removal and Installation

Inspect the O-ring seal (1) and replace it if damaged.

EMERGENCY SHUTOFF BUTTON REMOVAL
1. O-ring seal. 2. Plunger. 3. Spring. 4. Button.

Inspect the plunger (2) for wear or damage and replace it if necessary.

Guide Removal and Installation

GUIDE REMOVAL
1. Guide. 2. Cotter pins, washers, springs (two) and pins (two).

Worm Shaft and Slide Follower Removal and Installation

WORM SHAFT ASSEMBLY REMOVAL
1. Snap ring (earlier controls). 2. Worm shaft assembly.

NOTE: The shaft (6) is pressed into the housing (7). To remove the springs (3), slide follower (4) and tube (5), it is necessary to damage shaft (6). The ten coil spring is installed on the shaft at the release lever pin side of the slide follower as is the single twenty coil spring in earlier controls. The spring with six or seven coils is installed on later controls on the other side of the slide.

SLIDE FOLLOWER REMOVAL
3. Spring (earlier controls have one). 4. Slide follower. 5. Tube. 6. Shaft. 7. Housing.

Install in the reverse order of removal, pressing in a new shaft (6).

Release Rod Removal and Installation

Remove the seals and plug (3), then back off nut (2) and remove the cable, release rod (1) and nut (2) as an assembly.

NOTE: The plug (3) is a guide for the end of release rod (1) and retainer for the seal.

Install in the reverse order of removal.

RELEASE ROD REMOVAL
1. Release rod. 2. Nut. 3. Seal and plug.

Release Rod Disassembly and Assembly

Before disassembly, measure the distance from rod end to collar face. This distance should be 1.95 in. (49,53 mm) for 6L9237 and 8L5299 Controls; for 4L8129 Controls the measurement should be 1.89 in. (48,01 mm).

PREPARING TO DISASSEMBLE RELEASE ROD
1. Cable. 2. Nut. 3. Washer. 4. Spring. 5. Release rod.

1. To remove spring (4) and collar (7), drive out spring pins (8) (two on later controls).

2. To separate nut (2) from the cable assembly (1), drive out spring pin (6).

3. Inspect all parts for wear or damage and install new parts if necessary.

DISASSEMBLING RELEASE ROD
1. Cable. 2. Nut. 5. Release rod. 6. Spring pin. 7. Collar. 8. Spring pins (two on later controls).

NOTE: If a new released cable and rod assembly is installed, drill the spring pin hole (two spring pins on later controls) in the rod before assembly. Place the collar on the rod with counterbore of collar tightly over hex on the rod. Drill a 3/32 in. hole in rod using collar as a templet. After assembly the distance from rod end to collar face should be 1.95 in. (49,53 mm) for 6L9237 and 8L5299 Controls; for 4L8129 Control the measurement should be 1.89 in. (48,01 mm).

4. Assemble in the reverse order of disassembly.

NOTE: When the control is equipped with a stop bracket (9) for the reset lever, a .12 in. (3,05 mm) clearance (10) between the lever and bracket is required. Make adjustment to the length of release rod (5) to obtain this clearance.

RESET LEVER STOP CLEARANCE
5. Release rod. 9. Stop bracket. 10. Clearance of .12 in. (3,05 mm).

Release Lever Removal and Installation

PREPARING TO REMOVE RELEASE LEVER
1. Bolt.

RELEASE LEVER REMOVAL
2. Spring. 3. Lever.

Inspect all parts for wear or damage and replace any required.