3306 DIESEL TRUCK ENGINE Caterpillar

Too Much Exhaust Smoke - White Smoke; Blue Smoke


White Smoke

Recommended Procedure

1. Cold Outside Temperatures ... When the air outside is cold, the cylinder temperature is cooler. Not all the fuel will burn in the cylinders. The fuel which does not burn comes out the exhaust as white smoke. White smoke is normal in cold temperatures until the engine operates long enough to become warm. There will be less white smoke if No. 1 diesel fuel is used.
2. Long Idle Periods ... When an engine runs at idle speed for a long period of time, the cylinders cool and all of the fuel does not burn. Do not idle an engine for a long period of time. Stop an engine when it is not in use. If long idle periods are necessary, use No. 1 diesel fuel.
3. Low Quality Fuel ... Test the engine using fuel according to recommendations by Caterpillar Tractor Co.
4. 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 a fuel injection line nut at the cylinder head. With the governor lever in the shutoff position, operate the fuel priming pump until the flow of fuel from the loosened fuel injection line is free of air. Tighten the fuel line nut. Fasten the priming pump and start the engine. If the engine still does not run smooth or releases a large amount of white smoke, loosen the fuel line nuts one at a time at the cylinder head until the fuel that comes out is free of air. Tighten the fuel line nuts. If the air can not be removed in this way, put 5 psi (35 kPa) of air pressure to the fuel tank.


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

Check for leakage 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.

5. Fuel Injection Timing Not Correct ... Check and make necessary adjustments as per Testing and Adjusting section of this Service Manual.
6. Automatic Timing Advance Does Not Operate Correctly ... Check with engine warm. Use the 1P3500 Timing Light Group. Special Instruction Form No. SMHS6964 gives the test procedure. If the timing light is not available, make rapid "acceleration" (increase in speed) from low idle to high idle. Engine must have smooth acceleration. A timing advance that does not operate correctly can cause delays of the engine acceleration at some rpm before high idle, or possibly cause the engine to run rough and have exhaust noise (backfire) during acceleration. This condition is difficult to find if engine acceleration is slow or at a constant engine rpm.
7. Valve Adjustment Not Correct ... Check and make necessary adjustments as per Testing and Adjusting section of this Service Manual. Intake valve clearance is .015 in. (0.38 mm) and exhaust valve clearance is .025 in. (0.64 mm).
8. Bad Fuel Nozzle(s) ... Bad fuel nozzles will normally cause the engine to "misfire" (injection not regular) and run rough, but can cause too much smoke and the engine still be running smooth. Remove the fuel nozzles and test as per Testing and Adjusting section of this Service Manual.
9. Misfiring Cylinder(s) ... See Misfiring and Running Rough.

Blue Smoke

10. Engine Oil Level Too High ... Do not put too much oil in the crankcase. If the oil level in the crankcase goes up as the engine is used, check for fuel in the crankcase. See FUEL IN CRANKCASE OIL.
11. Worn Valve Guides ... See the Specifications section of this Service Manual for the maximum permissible wear of the valve guides.
12. Worn Piston Rings and/or Cylinder Walls- ... Worn piston rings and/or cylinder walls can be the cause of blue smoke and can cause a loss of compression. Make a visual inspection of the cylinder walls and piston rings. If necessary, measure the cylinder walls and piston rings. For the cylinder and piston ring specifications, see the Specification section of this Service Manual.

NOTE: High wear at low mileage is normally caused by dirt coming into the engine with the inlet air.

13. Wear or Damage to Pistons ... Check the piston ring grooves for wear. This engine can have piston grooves and rings of the KEYSTONE (taper) design. A special 5P4812 Piston Ring Groove Gauge is available to check the top two ring grooves in the piston. For instruction on use of the gauge, see the GUIDELINE FOR REUSABLE PARTS: PISTONS AND CYLINDER LINERS, Form No. SEBF8001. Pistons which have worn grooves and pistons with damage or defects can cause blue smoke and too much oil consumption. Make sure the oil return holes under the oil ring are open.
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