Troubleshooting

Troubleshooting can be difficult. On the following pages there is a list of possible problems. To make a repair to a problem, make reference to the cause and correction.

This list of problems, causes, and corrections, will only give an indication of where a possible problem can be, and what repairs are needed. Normally, more or other repair work is needed beyond the recommendations in the list.

Remember that a problem is not normally caused only by one part, but by the relation of one part with other parts. This list can not give all possible problems and corrections. The serviceman must find the problem and its source, then make the necessary repairs.

Troubleshooting Index

1. Engine Will Not Start.

2. Engine Will Start, But Shuts Down When Oil Pressure Override is Released.

3. Engine Will Only Run Below 70% of Rated Speed.

4. Air Inlet Shutoff Activates on Load Rejection.

5. Air Inlet Does Not Close.

6. Engine Will Not Restart After Operation of Emergency Manual Shutoff.

7. Engine Will Not Shutdown When Checking Low Engine Oil Pressure Protection Circuit.

8. Shutoff Control Unit Does Not Operate.

FIGURE 1. PROTECTIVE SYSTEM OIL LINES
1. Plug. 2. Oil line to thermostatic pilot valve. 3. Oil return line from diverter valve. 4. Oil supply line to diverter valve. 5. Oil drain line from diverter valve.

FIGURE 2. PROTECTIVE SYSTEM OIL LINES
2. Oil line to thermostatic pilot valve. 3. Oil return line from diverter valve. 4. Oil supply line to diverter valve. 5. Oil drain line from diverter valve. 6. Cover on actuator valve body.

Engine Will Not Start

Engine Will Start, But Shuts Down When Start-Up Override Is Released

Engine Will Only Run Below 70% Of Rated Speed

Air Inlet Shutoff Activities On Load Rejection

Air Inlet Does Not Close

Engine Will Not Restart After Operation Of Emergency Manual Shutoff

Engine Will Not Shutdown When Checking Low Engine Oil Pressure PROTECTION CIRCUIT

Shutoff Control Unit Does Not Operate

Hydramechanical Protective System

PROTECTIVE SYSTEM WITH ENGINE SHUTDOWN FOR ALL FUNCTIONS (LOP, HWT, OS)
1. Oil line to air inlet shutoff actuator. 2. Return line from air inlet shutoff actuator. 3. Oil line to thermostatic pilot valve. 4. Return line from diverter valve. 5. Oil line to diverter valve. 6. From two-way valve at the diverter valve to drain. 7. From diverter valve to governor (fuel) shutoff actuator.

Many engines run thousands of hours in continuous-duty applications without any operation of the protective system shutoff actuators, valves and alarms (if so equipped).

Every 500 Service Meter Units, the emergency manual shutoff should be operated. This will check the protective system for correct operation.

If no engine shutdown occurs, further inspection of the system is needed. The drive coupling and the two-way, 5N6411 Valve (palm valve) can be tested while the engine is operating under full load. However, tests of the air inlet shutoff and the (fuel) shutoff are done with the engine at low idle. Use th following procedures to check the system more completely.

Drive Coupling Check

Put a rag around the fitting to prevent oil spray on oil supply line (5) at the diverter valve.

Operate the engine at low idle and loosen the nut on the fitting at the diverter valve one-half to three-quarters of a turn. Shake the line to break the paint. If any oil comes out under pressure, the shutoff is being driven through the coupling. Tighten the nut.

PROTECTIVE SYSTEM WITH ENGINE SHUTDOWN FOR OVERSPEED ONLY, ALARMS FOR OTHER FUNCTIONS (LOP, HWT)
1. Oil line to air inlet shutoff actuator. 2. Return line from air inlet shutoff actuator. 3. Oil line to thermostatic pilot valve. 4. Return line from diverter valve. 5. Oil line to diverter valve. 6. From two-way valve at the diverter valve to drain. 7. From diverter valve to governor (fuel) shutoff actuator. 8. Oil pressure switch for alarms.

PROTECTIVE SYSTEM OIL LINES
3. Oil line to thermostatic pilot valve. 5. Oil line to diverter valve. 6. From two-way valve (at the diverter valve) to drain.

Start-Up Override Valve Check

On an engine with an air start system, start and operate the engine at low idle. Loosen the drain line from the two-way (palm) valve. There should be no oil present. If there is any oil flow, the valve has failed and replacement is necessary.

Air Inlet Shutoff Check

Operate the engine at low idle and pull the red, emergency knob. The air inlet shutoff valve must close and stop the engine. Low oil pressure and high coolant temperature alarms should also be activated, if so equipped.

The fuel shutoff actuator must also move the governor and fuel control linkage to the "SHUTOFF" position.

Fuel Shutoff Test

Hold open the air inlet shutoff valve with a length of wire. (If another person is present, the valve can be held open by hand.)

Pull the red, emergency knob. Since the air inlet shutoff valve has been held open, the fuel shutoff actuator should stop the engine. The low oil pressure, high coolant temperature alarms should also be activated, if so equipped.

Low Oil Pressure Test

Disconnect the oil supply line that is installed between the thermostatic pilot valve and the shutoff control group, at the control group. Attach a 3N4847 Hose Assembly to the control. Use a 7D5363 Connector to adapt a 3R3837 Shutoff Valve to the end of the hose.

NOTE: If the engine is not equipped with a thermostatic pilot valve, remove the plug from where line (4) would connect to the shutoff control group.

Close the valve and start the engine and operate it at low idle. The engine will run normally.

Place the end of the hose in a bucket or other container and open the valve to drain approximately one-half liter (one U.S. pint) of oil to lower the oil pressure.

This will actuate the low oil pressure protection circuit and cause engine shutdown through the fuel shutoff actuator or activate the low oil pressure, high coolant temperature alarms, if so equipped. The air inlet shutoff should not be activated by this test.

NOTE: The fuel shutoff actuator will not be activated in a protective system that gives overspeed protection only, when a low oil pressure fault is simulated.

If th fuel shutoff actuator is not activated by this test, check the actuator, oil lines or electrical connections, and the shutoff control group for defects. Make repairs or replacements of parts as needed.

If the alarms fail to activate, make sure the pressure switch on the control valve group, the wiring and alarms work correctly to locate and repair parts as needed.

Remove the hose assembly, connector and shutoff valve from the engine. Connect the oil supply to the thermostatic pilot valve.

All of the above tests are performed at low idle. Successful shutdowns and alarms at low idle indicate correct operation. Therefore, it is not necessary to perform the tests at high idle.

Shutoff Speed Setting Adjustment

NOTE: When major disassembly or adjustment of the shutoff control group is needed, see CATERPILLAR FUEL INJECTION TEST BENCH BOOK, FORM NO. SEHS7466 for the complete specifications and test bench procedures to use.

1. Check and make sure the engine fuel settings are correct. See FUEL SETTING CHECK in the Engine TESTING AND ADJUSTING section of this Service Manual.

2. Start the engine and operate it at low idle.

SHUTOFF CONTROL GROUP
1. Emergency manual shutoff. 2. Overspeed setting adjustment bolt.

3. Before any adjustment to the shutoff control overspeed setting is made, check for correct operation of the hydramechanical protective system. Pull emergency manual shutoff knob (1). Successful shutdown of intake air and fuel indicate correct operation.

4. Remove seal and wire from the bolts and remove the cover from over the high idle adjustment screw on the Caterpillar 3161 Governor, or the seal wire from high idle screw lock nut on Woodward UG-8L Governor.

5. Connect a tachometer of known accuracy to the engine.

NOTE: Some types of engine driven equipment, such as generators, pumps or compressors, can be damaged if operated at 18% above full load speed. If so, the driven equipment must be disconnected from the engine during this test. If this cannot be done, adjustment of the shutoff control group can be made on the CATERPILLAR FUEL INJECTION TEST BENCH. See Form No. SEHS7466 for the complete test bench procedures.

6. Start the engine again and operate it at high idle with no load.

7. Turn the governor high idle adjustment screw slowly to increase engine rpm. The air inlet shutoff must close and the fuel must be shut off through the governor and fuel control linkage at 18% ± 25 rpm above full load rpm. For example, this is 2124 ± 25 rpm for an engine rated at 1800 rpm.

8. If engine shutdown does not occur at 18% ± 25 rpm above full load rpm, slowly increase engine rpm 50 rpm more. For example, this is 2174 rpm for an engine rated at 1800 rpm. If engine shutdown still does not occur, decrease the engine rpm and remove the seal and lockwire and turn overspeed adjusting bolt (2) one turn counterclockwise. Again, slowly increase the engine rpm to check for engine shutdown at 18% ± 25 rpm above full load rpm.

UG-8L GOVERNOR
3. High idle adjustment screw.

ADJUSTMENT OF HIGH IDLE ON 3161 GOVERNOR

NOTE: If engine shutdown occurs before 18% ± 25 rpm of full load rpm, turn overspeed adjusting bolt (2) clockwise to increase the shutoff control group overspeed setting.

9. Repeat the above procedure until engine shutdown occurs at the correct rpm.

10. Adjust engine high idle to the specifications shown on the Engine Information Plate which is attached to one of the right side camshaft inspection covers. If the Engine Information Plate is missing, see the FUEL SETTING AND RELATED INFORMATION FICHE for the correct specifications to use.

11. Install the seals and lockwires for the shutoff control group and the governor high idle adjustment screw.

Hydramechanical Protective System Wiring Diagrams

ALT

ALTERNATOR

AMM

AMMETER

ASOS

AIR SHUTOFF SOLENOID

ASSV

AIR START SOLENOID VALVE

B-

BATTERY NEGATIVE

B+

BATTERY POSITIVE

BATT

BATTERY

CB

CIRCUIT BREAKER

EGA

ELECTRIC GOVERNOR ACTUATOR

EGC

ELECTRIC GOVERNOR CONTROL

ENCL

ENCLOSER

FSOS

FUEL SHUTOFF SOLENOID

HM

HOUR METER

HMMPU

HOUR METER MAGNETIC PICK-UP

HMOBSV

HYDRAMECHANICAL OIL BYPASS SOLENOID VALVE

HMOPS

HYDRAMECHANICAL OIL PRESSURE SWITCH

HMRSSV

HYDRAMECHANICAL REMOTE SHUTOFF SOLENOID VALVE

HWTAS

HIGH WATER TEMPERATURE ALARM SWITCH

LOPAS

LOW OIL PRESSURE ALARM SWITCH

LWTAS

LOW WATER TEMPERATURE ALARM SWITCH

MGOPG

MARINE GEAR OIL PRESSURE GAGE

MGOPSU

MARINE GEAR OIL PRESSURE SENDING UNIT

MGOTAS

MARINE GEAR OIL TEMPERATURE ALARM SWITCH

MPU

MAGNETIC PICK-UP

OPG

OIL PRESSURE GAGE

OPS

OIL PRESSURE SWITCH

OPSU

OIL PRESSURE SENDING UNIT

PB

PUSH BUTTON

PP

PRELUBE PUMP

PPMS

PRELUBE PUMP MAGNETIC SWITCH

PPPS

PRELUBE PUMP PRESSURE SWITCH

RNS

REMOTE NORMAL SHUTOFF SWITCH

SM

STARTER MOTOR

SMMS

STARTER MOTOR MAGNETIC SWITCH

TM

TACHOMETER

TMMPU

TACHOMETER MAGNETIC PICK-UP

TS

TERMINAL STRIP

WTG

WATER TEMPERATURE GAGE

WTS

WATER TEMPERATURE SWITCH

WTSU

WATER TEMPERATURE SENDING UNIT

B

BLACK

BR

BROWN

B/W

BLACK WITH WHITE STRIPE

CU

COPPER (BARE WIRE)

DK BL

DARK BLUE

DK GR

DARK GREEN

GR

GREEN

LT BL

LIGHT BLUE

O

ORANGE

O/B

ORANGE WITH BLACK STRIPE

P/B

PINK WITH BLACK STRIPE

PU/W

PURPLE WITH WHITE STRIPE

R

RED

W

WHITE

W/O

WHITE WITH ORANGE STRIPE

W/R

WHITE WITH RED STRIPE

Y

YELLOW

Y/BR

YELLOW WITH BROWN STRIPE

3500 ENGINE WIRING DIAGRAM (REF. 5N8944) (Earlier Systems With 5N9310 Pressure Switch Assembly)

3500 ENGINE WIRING DIAGRAM (REF. 5N8944) (Later Systems With 4W2188 Pressure Switch Assembly)

CUSTOMER WIRING WITH HYDRA-MECHANICAL SHUT-OFF GROUPS

NOTE A: Magnetic pick-up and oil pressure switch to be wired to electric governor control (Woodward 2301) with a two conducter shielded cable (Belden Corp. type 8780 or equivalent). Shields are to be grounded at electric governor control grounding stud. Each shield should not have more than one ground connection.

NOTE B: Woodward 2301 Electric Governor Control terminal identification chart:

NOTE C: Caterpillar alarm and prealarm contacts are rated for a maximum of 3 amps inductive at the charging system voltage.