Usage:
Misfiring And Running Rough
1. Intermittent Electrical Connection
Look at the "check engine" light on the dash to determine if there are any faults. See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913. If faults are found, follow the procedures to identify and correct the faults.
2. 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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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.
3. 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.
4. 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 (see Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913). If a cylinder is found where the cutout makes no difference on the engine performance, 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. SENR3914).
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. SEHS9120, Removal And Installation Of Unit Injector Sleeve.
The "check engine" light on the dash can be used to determine if there are any electronic system faults relating to the injectors. Fault codes 72, 73, 74, and 75 relate to the injector operation and wiring. See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.
5. Fuel Injection Timing Not Correct
Check the fuel injection timing calibration and make necessary adjustments. See the topics, Engine Test Procedure Number P-402, [Checking Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP (Electronic Control Analyzer and Programmer)], and Engine Test Procedure Number P-403, [Calibrating Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP (Electronic Control Analyzer and Programmer)], in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.
6. 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. SENR3909. 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.
7. 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. |
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- * 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.
8. 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. SENR3909.
9. 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. SENR3914.
10. 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. SEHS9120, Removal And Installation Of Unit Injector Sleeve. Torque the fuel injector hold down bolt to 30 ± 7 N·m (22 ± 5 lb ft).
11. Defective Injector Sleeve
Corrosion or cracks in the injector sleeve 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. SEHS9120, Removal And Installation Of Unit Injector Sleeve. Torque the fuel injector hold down bolt to 30 ± 7 N·m (22 ± 5 lb ft).