3176 MECHANICAL TROUBLESHOOTING Caterpillar

Mechanical Troubleshooting

Usage:

Abnormal Cooling System

Overheating

1. Defective Temperature Gauge

If the temperature gauge shows that the coolant temperature is above normal and all other conditions indicate that conditions are normal, check the coolant temperature in another method, such as:

* Read the coolant temperature with an ECAP or DDT.

* Install an 8T0470 Thermistor Thermometer Group

* Install a temperature sensitive tape.

* Install a new gauge that is known to be good.

2. Low Coolant Level

Low coolant level can cause overheating to occur. Low coolant level can be caused by leaks in the cooling system or by improper filling of the radiator. With the engine cool, the coolant level should be at the low end of the fill neck on the radiator. If the coolant is below this level, a visual inspection should be done to see if any leaks can be seen. If nothing obvious is seen, refer to the topic Loss Of Coolant in this section. Fill the radiator according to recommendations in the Operation & Maintenance Manual.

3. Dirty Radiator

Check for debris between the fins of the radiator core which could restrict the free flow of air through the radiator core. Also check for debris or deposits on the inside of the core which could restrict the free flow of coolant through the radiator. Clean out any debris that is found.

4. Fan Belt Slippage

Check for proper fan speed with the fan engaged. Check the belt tension. Check the belt tensioner bearing and spring for proper operation. Check the belt and pulleys for lubricant contaminants which could cause belt slippage. Check the belt for hardening and glaze caused by heat and slippage. Repair or replace any defective parts that are detected.

5. Faulty Fan Clutch

Check to verify that the fan clutch is engaging properly. Refer to the Truck Manufacturer's Service Manual for the proper procedure.

6. Defective Hoses

Check the hoses for leaks, cuts and loose clamps. Check for any hoses that are collapsed or restricted that could cause a decrease in the amount of flow of coolant through the engine or radiator. Replace as necessary.

7. Defective Pressure Cap

Inspect the sealing surface of the pressure cap and the radiator. Look for any damage to the seal or the sealing surface. Remove any foreign material and replace any defective seals. Check the sealing pressure of the cap with the Cooling System Pressurization Pump Group, 9S8140. This will check the opening pressure of the cap. If the cap is defective, replace it.

8. Shutters Not Functioning Correctly

Check the opening temperature of the shutters. The shutters must be completely open at a temperature below the fully open temperature of the water temperature regulator.

9. Defective Water Temperature Regulator

If the water temperature regulator is not opening properly or if the seal is damaged, it can cause the engine to overheat. Check the water temperature regulator for proper operation according to the test procedure for the thermostat located in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR5108.

10. Defective Water Pump

Check the water pump impeller for damage or looseness on the shaft. Also, see the topic, Cooling System, in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR5108.

11. Air/Combustion Gas In The Cooling System

Air/Combustion Gas in the cooling system reduces the heat transfer from hot engine parts to the coolant and causes low coolant flow. The most common causes of air are:

* Improper filling of the cooling system trapping air in the system.

* Combustion gas leaking into the system. If air/combustion gas is present in the cooling system, the engine should be checked for internal cracks (cylinder head, injector sleeve, cylinder liner) or for a defective cylinder head gasket.

* Air compressor leaking air to coolant.

Before testing, be sure the cooling system is filled correctly. Use a wire to hold the relief valve in the radiator cap open. Put the hose over the end of the overflow pipe. Start the engine and operate it at high idle rpm for a minimum of five minutes after the engine is at normal operating temperature. After five or more minutes at operating temperature, place the loose end of the hose in the bottle filled with water. If the water gets out of the bottle in less than forty seconds, there is too much exhaust gas leakage into the cooling system. Find the cause of the air or gas getting into the cooling system and correct as necessary.

12. Incorrect Fan, Fan Or Shroud Not In The Correct Position

The fan and shroud must be in the proper position to provide adequate flow of air to the radiator. The fan must be large enough to pull air through most of the area of the radiator core. Make sure the fan size, fan shroud, and position of the fan and shroud are according to the recommendations of the Truck Manufacturer.

13. Radiator Too Small

Check the recommendations of the Truck Manufacturer to be sure that the radiator is the proper size for the current power setting of the engine.

14. Air Restriction In The Engine Compartment

Check to make sure the filters, air conditioners, and other equipment are mounted in the engine compartment in such a way that they do not interfere with the flow of air into and out of the compartment.

15. High Outside Temperature

If there is not a large enough difference between the outside air temperature and the coolant temperature, the cooling system may not be capable of cooling the engine. To get better cooling, the truck can be operated in a lower gear to increase the speed of the cooling fan and the water pump, or a reduced vehicle speed to reduce the HP requirement.

16. Operation At High Altitude

The boiling point of the coolant decreases as the altitude the vehicle is operated at increases. Proper cooling system pressure must be maintained to prevent the coolant from boiling. If the truck is going to be used at a higher altitude for extended periods of time, a higher pressure radiator cap should be used.

17. Engine Used At A Lug Condition

"Lugging" the engine causes the engine rpm and fan rpm to operate slower. Low engine rpm will cause a reduction in coolant flow and air flow that may cause the engine to overheat. If the engine temperature is rising into a critical area, downshift the truck to a lower gear to provide increased engine rpm.

18. Air Inlet Restriction

Restriction of the air coming into the engine causes higher cylinder temperatures and raises the temperature of the coolant. Check for a restriction in the system. Air flow through the air cleaner must not have a restriction (negative pressure difference measurement between atmospheric air and air that has gone through air cleaner) of more than 635 mm (25 in) of water with a used or plugged air cleaner element. Air flow through the air cleaner must not have a restriction (negative pressure difference measurement between atmospheric air and air that has gone through air cleaner) of more than 381 mm (15 in) of water with a new air cleaner element.

19. Exhaust Restriction

A restriction in the exhaust will cause the engine temperature to increase due to higher cylinder temperatures. Make a visual inspection of the exhaust system to check for damaged piping or for a defective muffler. If no damage is found, the system should be checked for excessive back pressure. The back pressure must not exceed 1016 mm (40 in) of water. A simple visual check can be made by disconnecting the exhaust pipe from the turbocharger. Run the engine with the pipe disconnected to see if the problem has been corrected.

20. Fuel Injection Timing Not Correct

Check and make the necessary calibrations to the fuel injection timing. See Engine Test Procedure Number P-301 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

21. Shunt Line Restriction

Check for restriction in the shunt line from the radiator top tank to the water pump. A restriction can cause a lower coolant flow and overheating.

22. Transmission Problems

Verify that the power-shift or automatic transmission is in proper adjustment and is operating properly as per the manufacturer's Service Manual. A transmission that is out of adjustment will cause additional heat to be transferred to the engine cooling system.

23. Engine Power Set Too High

Make sure the radiator size complies with the Truck Manufacturer's recommendations for the current engine power setting. Check the power settings of the engine with an ECAP to make sure they agree with the specification plate.

Overcooling

24. Defective Temperature Gauge

If the temperature gauge shows that the coolant temperature is below normal and all other conditions indicate that conditions are normal, check the coolant temperature in another method, such as:

* Install an 8T0470 Thermistor Thermometer Group

* Install a temperature sensitive tape.

* Install a new gauge that is known to be good.

25. Long Idle Periods

Running the engine for extended periods of time under no load conditions will cause the engine heat to dissipate at a faster rate than it is being generated.

26. Very Light Loads

Very light loads, very slow speeds, or downhill travel can cause below normal heating due to the decreased amount of fuel that is being burned. The installation of shutters will help correct this problem by decreasing the flow of air into the engine compartment.

27. Defective Water Temperature Regulator

If the water temperature regulator is stuck open, it will cause below normal engine heating. To test the thermostat, see the topic, Testing The Cooling System, in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR5108.

28. Faulty Fan Clutch (Will Not Disengage)

Check for proper operation of the fan clutch. Refer to the Truck Manufacturer's Service Manual for the proper procedure.

29. Vent Line Unrestricted

If the vent line (OEM) between the temperature regulator and the radiator top tank is unrestricted, overcooling could result. If overcooling continues, install a valve assembly in the line that will allow air venting but restrict coolant flow with the engine running. The vent line should be orificed to 4.8 mm (0.19 in).

Loss Of Coolant

External Leaks

Pressurize the cooling system using the 9S8140 Cooling System Pressurizing Pump Group and check the following:

1. Leaks In Hoses Or Connections

Check all hoses and connections for visual signs of leakage. If no leaks are found, look for damage to hoses or loose hose clamps. NOTE: Also, check for leaks in accessories such as fuel heaters and transmission oil coolers.

2. Leaks In The Radiator And/Or Expansion Tank

3. Leaks In The Heater

4. Leaks In The Water Pump

Check the water pump for leaks before starting the engine, then start the engine and look for leaks. If there are leaks at the water pump, repair the pump or install a new pump.

5. Cylinder Head Gasket Leaks

Look for leaks along the surface of the cylinder head gasket. If leaks are found, remove the cylinder head and install a new head gasket.

6. Air Compressor Leaks

Coolant Leaks At The Overflow Tube

7. Defective Pressure Cap Or Relief Valve

Check the sealing surfaces of the pressure cap and the radiator to be sure the cap is sealing correctly. Check the opening pressure and sealing ability of the pressure cap or relief valve with the 9S8140 Cooling System Pressurizing Pump Group.

8. Engine Runs Too Hot

If coolant temperature is too high, pressure will be high enough to move the cap off of the sealing surface in the radiator and cause coolant loss through the overflow tube. If this occurs, refer to the portion, Overheating, of the topic, Abnormal Cooling System.

9. Expansion Tank Too Small Or Installed Incorrectly

The expansion tank can either be a part of the radiator or it can be installed separately from the radiator. The expansion tank must be large enough to hold the expansion of the coolant as it gets warm or has sudden changes in pressure. Verify that the expansion tank is installed correctly and that it is the proper size according to the specifications of the Truck Manufacturer.

10. Air/Combustion Gas In The Cooling System

Air/Combustion Gas in the cooling system reduces the heat transfer from hot engine parts to the coolant and causes low coolant flow. The most common causes of air are:

* Improper filling of the cooling system trapping air in the system.

* Air compressor leaking air to coolant.

The cooling system can be checked for air using the BOTTLE TEST. The equipment needed to do this test is a one pint bottle, a bucket of water, and a hose which will fit the end of the overflow pipe of the radiator. Before testing, be sure the cooling system is filled correctly. Use a wire to hold the relief valve in the radiator cap open. Put the hose over the end of the overflow pipe. Start the engine and operate it at high idle rpm for a minimum of five minutes after the engine is at normal operating temperature. After five or more minutes at operating temperature, place the loose end of the hose in the bottle filled with water. If the water gets out of the bottle in less than forty seconds, there is too much exhaust gas leakage into the cooling system. Find the cause of the air or gas getting into the cooling system and correct as necessary.

Internal Leakage

If coolant is found in the engine oil check the following internal components for damage:

11. Cylinder Head Gasket Leakage

If the cylinder head gasket leaks between a water passage and an opening into the crankcase, coolant will enter the crankcase.

12. Cracks In The Cylinder Head

Cracks in the upper surface of the cylinder head, or in an area between a water passage and an opening into the crankcase, can allow coolant to enter the crankcase.

13. Cracks In The Spacer Block

Cracks in the spacer block between a water passage and an opening into the crankcase can allow coolant to enter the crankcase.

14. Cylinder Liner Leakage

A damaged or missing liner seal can allow coolant to enter the crankcase. Replace any seals as needed. A cracked cylinder liner can also allow coolant to enter the crankcase. Check the liner for cracks and replace as necessary.

If coolant is found in the fuel or fuel in the coolant, remove the unit injectors and check the injector sleeves for cracks.

15. Defective Injector Sleeve

Corrosion or cracks in the injector sleeve can permit fuel to enter the coolant and also can allow coolant to enter the fuel supply manifold. It is also possible for combustion gas to enter the cooling system due to a leak in the injector sleeve. When this condition exists, the coolant level generally increases and exits the overflow.

Engine Will Not Start

Crankshaft Turns

1. Install the Electronic Control Analyzer and Programmer (ECAP) or the Digital Diagnostic Service Tool (DDT). See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

2. Electronic Self Check. Check the electronics diagnostic lamp on the dash to determine if there are any faults in the engine electronics system. Repair or replace parts as needed. See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

3. Check all wiring harness connectors.

NOTE: Connectors can be forced together with pins out of sequence.

4. Check Cranking Speed Of Crankshaft. Using the ECAP or DDT, check the speed of the crankshaft while the starter is cranking. If the crankshaft speed is below 250 rpm, then proceed to item 5. If the crankshaft speed is above 250 rpm, then proceed to item 6. If no rpm is displayed, refer to Engine Test Procedure Number P-102 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

5. Possible Causes Of Low Cranking Speed:

A. Low Battery Voltage

Check battery voltage. If the voltage is less than 8 volts for a 12 volt system, or 16 volts for a 24 volt system, put a charge to the battery. If the battery will not hold a charge, load test the battery. Use the 4C4911 Battery Load Tester and make reference to Operating Manual, Form No. SEHS9249 for complete information on use of the 4C4911 Battery Load Tester.

B. Defective Cable, Battery To Starter, Or Defective Connection

With ignition switch in the START position, check the voltage at the connection of the battery cable to the starter. If there is no voltage, or if the voltage is low at this connection and there is good voltage at the battery, check for a defective cable or connection between the battery and the starter.

C. Oil Too Thick For Free Crankshaft Rotation

Refer to the 3176 Truck Engine Operation And Maintenance Manual, Form No. SEBU6163 for the correct SAE grade oils for the ambient temperatures at which the engine is being operated. At temperatures below -23°C (-10°F), it may be necessary to warm the oil for free crankshaft rotation.

D. Defective Starter Motor

Remove and test. Make repairs as necessary or install a new starter motor.

E. Extra Outside Loads.

Damage to the power take-off equipment (if so equipped) and/or transmission can put extra load on the engine and prevent free rotation of the crankshaft. To check, disconnect the transmission and power take-off, and start the engine.

F. Transmission Or Power Take-off Problem

See the Truck Manufacturer's Service Manual.

G. Internal Engine Problem

Disassemble the engine and check all components for damage. See 3176 Diesel Truck Engine Disassembly And Assembly, Form No. SENR5109.

6. Can Exhaust Smoke Be Seen While Starting?

If exhaust smoke can be seen while starting the engine, then proceed to item 7. If exhaust smoke cannot be seen while starting the engine, then proceed to item 8.

7. Possible Causes-Engine Will Not Start

A. Cold Outside Temperatures

If temperatures are at or below 0°C (32°F) it may be necessary to use starting aids. It may also be necessary to heat the engine oil, fuel and coolant.

B. Air In Fuel System

With air in the fuel system, the engine will normally be difficult to start, run rough, and release a large amount of white smoke. If the engine will not start, loosen the highest drain plug on the front end of the fuel manifold. Operate the fuel priming pump until the flow of fuel from the loosened drain plug is free of air. Tighten the drain plug. If the air cannot be removed in this way, put 35 kPa (5 psi) of air pressure to the fuel tank.

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NOTICE

Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.

Check for leaks at the connections between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the lines. If there are no visual leaks, remove the fuel supply line from the tank and connect it to an outside fuel supply. If this corrects the problem, the suction line (standpipe) inside the fuel tank has a leak.

C. Poor Quality Fuel

Remove a small amount of fuel from the tank and check for water or other contamination in the fuel. See Special Instruction, Form No. SEHS7067 for complete information on fuel recommendations for Caterpillar diesel engines. If there is water in the fuel, remove the fuel until it is free of water. Fill with good quality fuel. Change the fuel filter and prime the system using the fuel priming pump. If there is water in the fuel, use an outside source of good quality fuel, prime and start the engine. If the engine starts easily, remove all the fuel from the fuel tank and fill with good quality fuel. Prime the fuel system if necessary.

D. Low Fuel Pressure

Change the fuel filter. If the pressure remains low, check the by-pass valve in the fuel transfer pump and the fuel pressure regulating valve in the fuel manifold adapter. Debris in the system can cause the valves to remain in the open position.

E. Fuel Injection Timing Out Of Calibration

Check the fuel injection timing calibration and make necessary calibrations. See Engine Test Procedure Number P-301 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

F. Valve Adjustment Not Correct

Check and make necessary adjustments. See the topic, Valve Clearance Setting, in 3176 Diesel Truck Engine Systems Operation And Testing and Adjusting, Form No. SENR5108. Intake valve clearance is 0.38 mm (.015 in), and exhaust valve clearance is 0.64 mm (.025 in). Also check for bent or broken push rod or other valve train parts.

G. Defective Unit Injector(s)

Testing of the injectors must be done off of the engine. Use the 1U6661 Pop (Injector) Tester Group with a 1U6663 Injector Holding Block, and a 1U6665 Power Supply, to test the injectors. For the test procedure refer to Special Instruction, Form No. SEHS8867, Using The 1U6661 Pop (Injector) Tester. For test specifications refer to Special Instruction, Form No. SEHS8804, Unit Injector Test Specifications for 1.7 Liter Engines.

NOTE: Inspect and repair as necessary the sealing surface (seat) of the injector sleeve in the cylinder head when removing and installing an injector. The injector sealing surface (seat) must be free of scratches or evidence of combustion products. If it is necessary to rework (ream) or replace the sleeve use 4C4054 Tool Group and refer to Special Instruction, Form No. SEHS9246, Using The 4C4054 Unit Injector Sleeve Replacement Tool Group.

H. Low Compression

See the topic, Misfiring and Running Rough in this publication.

8. Possible Causes-Engine Will Not Start

A. No Fuel In Tank(s)

Visually check fuel level in the tank(s). Be sure the tank selection valve is open for the tank with fuel in it. Be sure the fuel line between the tanks (if more than one) is open.

B. Electronic Malfunction

See Engine Test Procedure Number P-102 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

C. No Fuel From Unit Injectors.

a. Prime the fuel system per item 6B.

b. If temperatures are below -12°C (10°F), a poor quality fuel can "wax" and cause a restriction in the system. Install a new fuel filter. It may be necessary to drain the entire fuel system and replace with No. 1 grade fuel, or a blend of fuel depending on the air temperature.

c. Check for a fuel supply line restriction by removing the fuel supply line from the fuel filter base. Put 35 kPa (5 psi) of air pressure to the fuel tank.

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NOTICE

Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.

If there is no flow or a weak flow of fuel from the supply line, clean or replace plugged lines.

d. Check fuel transfer pump pumping gears and drive gear on the camshaft. Repair or replace as necessary. See 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109.

e. Drain the fuel manifold, remove each unit injector (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109) and bench test unit injectors to check flow. Replace plugged unit injectors.

D. Restriction In Exhaust System

Loosen the exhaust pipe from the exhaust manifold and start engine. If the engine starts easily, check the exhaust system for damage and/or restrictions.

Crankshaft Does Not Turn

9. Possible Causes-Engine Will Not Start

A. No Battery Voltage

Check battery voltage. If there is no battery voltage, put a charge to the battery. If battery will not hold a charge, load test the battery. Use the 4C4911 Battery Load Tester and make reference to Operating Manual, Form No. SEHS9249 for complete information on use of the 4C4911 Battery Load Tester.

B. Defective Switch, Defective Wiring Or Connection In Switch Circuit

With the ignition switch in the "start" position, check the voltage at the switch connection on the starter solenoid. If there is no voltage, or if the voltage is low at this connection, check the wiring, connections, ignition switch, and magnetic switch (if used).

C. Defective Cable, Battery To Starter, Or Defective Connection

With the ignition switch in the "start" position, check the voltage at the connection of the battery cable to the starter. If there is no voltage, or if the voltage is low at this connection and there is good voltage at the battery, check for defective cable or connection between the battery and the starter.

D. Defective Starter Solenoid

Remove and repair a solenoid which does not work when the voltage is correct at both the battery and switch connections on the starter solenoid.

E. Defective Starter Motor

If the solenoid works, but the starter motor does not turn the crankshaft, the starter motor is defective. Remove the starter motor (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109), and try to turn the crankshaft by hand (to be sure a mechanical failure inside the engine, transmission, or power take-off is not preventing the crankshaft from turning). If the crankshaft turns freely by hand, install the starter motor and engage the starter motor again. If the starter motor still will not turn the crankshaft, remove the starter motor. Repair the starter motor, or install a new one.

F. Transmission Or Power Take-Off Problem

If the crankshaft cannot be turned by hand, disconnect the transmission and power take-off (if so equipped). If the crankshaft will now turn, find the cause of the problem in the transmission or power take-off and make necessary corrections.

G. Hydraulic Cylinder Lock

Drain the fuel supply manifold, remove each unit injector (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109), and check for fluid in the cylinders while turning the crankshaft. Find root cause of the fluid and make the necessary repairs. The fluid must be removed (to prevent hydraulic cylinder lock) prior to reinstalling the unit injectors.

H. Defective Ring Gear

If the starter is working properly, but the crankshaft still does not turn, some of the teeth on the ring gear may be missing. Inspect the ring gear and replace if needed (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109).

I. Internal Engine Problem

If each of the above items have been checked and are not the problem, the engine must be disassembled (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109) to check for internal problems. Some of these internal problems may be bearing seizure, piston seizure, or valves making contact with pistons.

Fuel In Crankcase Oil

1. Defective Upper O-ring On Unit Injectors Or Leaking Unit Injector

Using the fuel priming pump, pressurize the fuel system to 689 kPa (100 psi). Check for fuel on the top deck of the cylinder head (a small amount of leakage is normal from the injector plunger barrel area after 5 minutes of constant pressure). If fuel is found, drain the fuel supply manifold. Remove each unit injector (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109), and check for a defective upper O-ring on the unit injector or if the unit injector itself is leaking.

A bad injector to sleeve seat causes combustion gas leakage that can damage the injector o-rings. Inspect injector hold down bolt thread depth for a minimum of 25 mm (0.984 in) of thread depth in the cylinder head.

2. Injector Not Seated Properly

Torque fuel injector hold down bolt to 30 ± 7 N·m (22 ± 5 lb ft).

3. Crack(s) In Cylinder Head

Pressurize the fuel gallery and check for crack(s). Crack(s) between the cylinder head fuel passages and passages open to the crankcase will allow fuel to enter the crankcase.

4. Porosity In Cylinder Head

Pressurize the fuel gallery and check for porosity. Leakage may be due to the proximity of the hole to internal fuel passages.

Fuel In Coolant

The injector sleeve seals the engine coolant from the low pressure fuel system. If there is a leak path and the engine is running, the higher pressure fuel is forced into the lower pressure cooling system. If the engine is off, the remaining cooling system pressure may force coolant into the low pressure fuel system.

To troubleshoot fuel in the coolant (or coolant in the fuel) remove the injectors and pressurize the cooling system to 103 kPa (15 psi). Inspect the injector sleeves for the following:

1. Cracked Or Pitted Injector Sleeves

2. Bad Sleeve To Head Joint

NOTE: May have to leave pressure on cooling system up to 30 minutes.

3. Cracked Or Porous Cylinder Head

Make all injector sleeve repairs using the 4C4054 Unit Injector Sleeve Replacement Tool Group. Refer to Special Instruction, Form No. SEHS9246, Using The 4C4054 Unit Injector Sleeve Replacement Tool Group.

Misfiring And Running Rough

1. Poor Quality Fuel

If poor or low quality fuel is suspected, use a source of known good quality fuel, prime and start the engine. If the problem is resolved, drain the complete fuel system, replace the fuel filter, and add fuel recommended by Caterpillar.

2. Low Fuel Pressure

Measure the fuel transfer pump pressure at rated engine rpm. The 1U5470 Engine Pressure Group can be used to measure the fuel transfer pump pressure. The 1U5470 Engine Pressure Group has a gauge to read fuel pressure to the fuel supply manifold. Special Instruction, Form No. SEHS8907 is with the tool group and gives information for its use.

NOTE: The ECAP or the DDT can also be used to check the fuel transfer pump pressure.

If the fuel transfer pump pressure is below 445 kPa (65 psi) at rated rpm, check for:

* Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc).

* Air in the fuel.

* Fuel transfer pump wear or damage. Refer to Specifications, 3176 Diesel Truck Engine, Form No. SENR5107.

* Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.

3. Air In Fuel System

Disconnect the fuel return line at the tank. Place this end of the line in a container of fuel to see if air bubbles are present while the engine is running. If air bubbles are observed, check for loose fittings or line leaks between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the line(s).

To remove air from the engine fuel system: With the engine off, loosen the fuel return line fitting at the fuel manifold. Operate the fuel priming pump until the flow of fuel is free of air. Tighten the return line fitting, fasten the priming pump, and start the engine. If the engine still does not run smooth or produces a lot of white smoke, apply 35 kPa (5 psi) of air pressure to the fuel tank to force fuel through the system.

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NOTICE

Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.

Check the fuel return line for restriction. Replace if it is plugged.

4. Injector Not Seated Properly

Leakage due to a loose injector or inadequate injector/sleeve sealing can cause combustion gas to enter the fuel supply manifold. Inspect and repair as necessary the sealing surface (seat) of the injector sleeve. The injector sealing surface (seat) must be free of scratches or evidence of a combustion leak (carbon). If it is necessary to rework (ream) or replace the sleeve use 4C4054 Tool Group and refer to Special Instruction, Form No. SEHS9246, Using The 4C4054 Unit Injector Sleeve Replacement Tool Group. Torque the fuel injector hold down bolt to 30 ± 7 N·m (22 ± 5 lb ft).

5. Defective Unit Injectors

A defective unit injector can be found using the Electronic Control Analyzer and Programmer (ECAP) and the timing adapter tool group. Run the engine at the rpm where the problem exists. Use the Interactive Diagnostics feature (single cylinder cutout) to stop the fuel supply to each cylinder in turn (see Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112). If a cylinder is found where the cutout makes no difference on the engine performance or does not increase the length of the injection duration bars for the other cylinders, that injector should be removed and tested. Drain the fuel supply manifold and remove the injector(s) (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109).

The diagnostic lamp on the dash can be used to determine if there are any electronic system faults relating to the injectors. Fault codes 72, 73 and 74 relate to the injector operation and wiring. See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

6. Fuel Injection Timing Not Correct

Check the fuel injection timing calibration and make necessary calibrations. See Engine Test Procedure Number P-301 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

7. Valve Adjustment Not Correct

8. Electronic System Malfunction

Use ECAP or DDT to determine if there are any fault codes. See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112. If faults are found, follow the procedures to identify and correct the faults. If no faults are found refer to Engine Test Procedure Number P-103 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

9. Cylinder Head Gasket Leakage

A defective head gasket can allow combustion gases to leak to:

* The exterior of the engine and can be visually detected.

* A coolant passage resulting in combustion gas in the coolant. This could cause a coolant loss through the radiator overflow. Remove the radiator filler cap, with the engine running, and check for air bubbles in the coolant caused by exhaust gases.

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Do not loosen the filler cap or pressure cap on a hot engine. Steam or hot coolant can cause severe burns.

* An adjacent cylinder. With this case two cylinders would misfire. Drain the fuel supply manifold, remove the injectors, and pressurize one of the cylinders and listen for leaking air from the other cylinder.

10. Camshaft Timing Not Correct

Camshaft timing can be checked by observing the timing marks on the front gear group. See the topic, Static Check Of The Timing Gear Position Used To Reference Electronic Injection Timing / Front Gear Group Alignment, in the Testing and Adjusting section of Systems Operation, Testing and Adjusting, Form No. SENR5108.

11. Valve Leakage; Wear Or Damage To Pistons And/Or Piston Rings; Wear Or Damage To Cylinder Liners

Refer to 3176 Diesel Truck Engine Disassembly and Assembly, Form. No. SENR5109.

Too Much Black Or Gray Exhaust Smoke

Engine Runs Smoothly

1. Poor Quality Fuel

If poor or low quality fuel is suspected, use a source of known good quality fuel, and prime and start the engine. If the problem is resolved, drain the complete fuel system, replace the fuel filter, and add fuel recommended by Caterpillar.

2. Fuel Injection Timing Out Of Calibration

Check the fuel injection timing calibration and make necessary calibrations. See Engine Test Procedure Number P-301 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

3. Air Inlet Piping Damage Or Restriction

Visually inspect the air inlet system for damage or restriction. If leaks are found, repair or replace parts as required.

If the air cleaner has an Air Cleaner Service Indicator, check the indicator for the position of the red piston. If the indicator shows red at any time, install a clean or new air cleaner element.

Air inlet restriction can be checked with a water manometer or a vacuum gauge [measuring mm (inches) of water]. Make a connection to the piping between the air cleaner and the inlet to the turbocharger. The maximum restriction allowed, with the engine at full load rpm, is 635 mm (25 in) of water. If a water manometer or vacuum gauge is not available, visually check the air filter for dirt. Clean or replace as required.

4. Exhaust System Restriction

Visually inspect the exhaust system for damage or restriction. If leaks are found, repair or replace parts as required.

Exhaust system back pressure (pressure differential between the turbocharger exhaust outlet and atmosphere) should not exceed 1016 mm (40 in) of water. An alternative check would be to remove the exhaust piping, load the engine on a chassis dynamometer to determine if the problem is corrected. If this solves the problem, the restriction is in the muffler or truck piping.

5. Valve Adjustment Not Correct

Check and make any necessary adjustments. See the topic, Valve Clearance Setting, in 3176 Diesel Truck Engine Systems Operation And Testing and Adjusting, Form No. SENR5108. Intake valve clearance is 0.38 mm (.015 in), and exhaust valve clearance is 0.64 mm (.025 in).

6. Defective Unit Injectors

A defective unit injector can be found, by running the engine at the rpm where the problem exists, with the use of the Electronic Control Analyzer and Programmer (ECAP) service tool Interactive Diagnostics feature (single cylinder cutout) to stop the fuel supply to each cylinder in turn. If a cylinder is found where the cutout makes a difference in exhaust smoke, that injector should be removed and tested. Drain the fuel supply manifold and remove the injector(s) (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109).

Engine Runs Rough

7. Misfiring and Running Rough

See the topic, Misfiring and Running Rough in this publication.

Too Much White Or Blue Exhaust Smoke

White Smoke

1. Cold Outside Temperature

White smoke is normal in cold temperatures until the engine warms up. There will be less white smoke if No. 1 diesel or blended fuel is used.

2. Engine Running Too Cold

Check the water temperature gauge in the cab. If the temperature remains below the minimum value of the gauge after a reasonable warm up time, this could indicate an open thermostat. Remove and test the thermostat. See the topic, Testing The Cooling System, in 3176 Diesel Truck Engine Systems Operation And Testing and Adjusting, Form No. SENR5108.

3. Air In Fuel System

Disconnect the fuel return line at the tank. Place this end of the line in a container of fuel to see if air bubbles are present when the engine is running. If air bubbles are observed, check for loose fittings or line leaks between the fuel tank and fuel transfer pump. If leaks are found, tighten the connections or replace the lines.

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NOTICE

Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.

Check the fuel return line for restriction. Replace if plugged.

5. Fuel Injection Timing Out Of Calibration

Check the fuel injection timing calibration and make necessary adjustments. See the topics, Engine Test Procedure Number P-221 and P-301 in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112.

6. Valve Adjustment Not Correct

7. Defective Unit Injectors

A defective unit injector can be found, by running the engine at the rpm where the problem exists, with the use of the Electronic Control Analyzer and Programmer (ECAP) service tool Interactive Diagnostics feature (single cylinder cutout, see Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR5112) to stop the fuel supply to each cylinder in turn. If a cylinder is found where the cutout makes a difference in exhaust smoke, that injector should be removed and tested. Drain the fuel supply manifold and remove the injector(s) (see 3176 Diesel Truck Engine Disassembly and Assembly, Form No. SENR5109).

8. Misfiring Cylinder(s)

See the topic, Misfiring and Running Rough in this publication.

Blue Smoke

9. Engine Oil Level Too High

Check the crankcase oil level. Maintain the level between the FULL and ADD marks on the dipstick. Refer to "Dipsticks", in the Operation Section of the Operations And Maintenance Manual, Form No. SEBU6163 for calibration of the dipstick. If the oil level increases as the engine is used, check for fuel in the crankcase. See the topic, Fuel In Crankcase Oil in this publication.

10. Worn Valve Guides; Worn Or Damaged Pistons, Rings And/Or Liners, Turbo Shaft Seal Leakage

Oil leakage into the combustion area of the cylinder(s) can be the cause of blue smoke. Inspection of these components will require engine disassembly. Refer to 3176 Diesel Truck Engine Disassembly and Assembly, Form. No. SENR5108. See 3176 Diesel Truck Engine Specifications, Form No. SENR5107 for the maximum permissible wear of the valve guides.