3208 TRUCK ENGINE Caterpillar

Too Much Exhaust 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 with 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. To remove the air from the fuel system open the manual bleed valve on the fuel injection pump housing. Operate the priming pump until the flow of fuel from the manual bleed valve is free of air. Close the manual bleed valve and fasten the fuel priming pump. 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 heads, and permit the fuel to come out until it is free of air. Tighten the fuel line nuts. If air is not removed in this way, put 5 psi (35 kPa) [CAUTION do not use more than 8 psi (55 kPa)] of air pressure to the fuel tank and check for leaks at connections between the fuel tank and the fuel transfer pump. If there are no leaks at the connections, remove the fuel supply line from the tank and connect it to an outside fuel supply. If this corrects the problem in 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 (GMG00501) 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 adjustment is .015 in. (0.38 mm) and exhaust valve adjustment is .025 in. (0.64 mm).

8. Bad Fuel Nozzle(s) - Bad fuel nozzles will normally cause the engine to "misfire" (ignition 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 Cylinders(s) - See the chart 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 the chart FUEL IN CRANKCASE OIL.

11. Damage to Positive Crankcase Ventilator Valve or Valve Assembled Wrong - The positive crankcase ventilator valve must be assembled correctly and the diaphragm and/or gasket must be free of damage.

12. Worn Valve Guides - See the Specifications section of this Service Manual for the maximum permissible wear of the valve guides. The repair procedure for valve guides is in the Reconditioning Procedures section of this Service Manual.

13. 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. Check cylinder condition with the cylinder leakage tester. Special Instruction (GMG00694) gives the test procedure. 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.

14. Wear or Damage to Pistons - Check piston ring to groove clearance. 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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