Usage:
Engine Runs Smoothly
Possible Causes/Corrections
Dirty Air Cleaner
If the air cleaner has a restriction indicator, see if the red piston is in view. If there is no restriction indicator, restriction can be checked with a water manometer or a vacuum gauge (which measures in inches of water). Make a connection to the piping between the air cleaner and the inlet of the turbocharger. Check with the engine running at full load rpm. Maximum restriction is 635 mm (25 in) of water. If a gauge is not available, visually check the air cleaner element for dirt. If the element is dirty, clean the element or install a new element.
Air Inlet Piping Damage or Restriction
Make a visual inspection of the air inlet system and check for damage to piping, rags in the inlet piping, or damage to the rain cap or the cap pushed too far on the inlet pipe. If no damage is seen, check inlet restriction with a clean air cleaner element.
Exhaust System Restriction
Make a visual inspection of the exhaust system. Check for damage to piping or for a bad muffler. If no damage is found, you can check the system by checking the back pressure from the exhaust (pressure difference measurement between exhaust outlet and atmosphere). The back pressure must not be more than 1016 mm (40 in) of water. You can also check by removing the exhaust pipes from the exhaust manifolds. With the exhaust pipes removed, start and load the engine on a chassis dynamometer to see if the problem is corrected.
Fuel Injection Timing Not Correct
Check and make necessary adjustments as in Testing and Adjusting section of this Service Manual.
Fuel Setting Is Not Correct
Check and make necessary adjustments as in Testing and Adjusting section of this Service Manual. See the Fuel Setting And Related Information Fiche for the correct fuel setting.
Low Quality Fuel
Test the engine with fuel according to recommendations by Caterpillar Inc. For more information see Special Instruction, Form No. SEHS7067, Fuel Recommendations For Caterpillar Diesel Engines. Also, Special Instruction, Form No. SEHS6947 has fuel correction factors and tables.
Bad Fuel Nozzle(s)
Bad fuel nozzles will normally cause the engine to misfire and run rough, but can cause too much smoke with engine still running smooth. Remove the fuel nozzles and test as in Testing and Adjusting section of this Service Manual.
Wrong Seal Washer Installed Under Nozzle(s)
The use of incorrect washers change the location of the fuel injection nozzles in the combustion chamber. This effects smoke. Check the Engine Arrangement for the correct part number to use.
Valve Adjustment Not Correct or Valve Leakage
Check and make necessary adjustments as in Testing and Adjusting section of this Service Manual. Intake valve clearance is 0.38 mm (.015 in) and exhaust valve clearance is 0.76 mm (.030 in). Valve leakage normally causes the engine to misfire and run rough.
Bad Fuel Injection Pump
An injection pump can have a good fuel flow coming from it but cause rough running because of slow timing that is caused by wear on the bottom end of the plunger. See the Testing and Adjusting section in this Service Manual for the correct specifications and procedure to check the plungers and lifters.
Fuel pumps which are severely scored from debris can cause rough running, but fuel dilution usually occurs before horsepower is affected.
Low installation torque on the fuel pump retaining nut can cause misfire, rough running and low power.
Engine Runs Rough
Possible Causes/Corrections
Misfiring Cylinder(s)
See Misfiring and Running Rough.
Fuel Injection Timing Not Correct
Check and make necessary adjustments as in Testing and Adjusting section of this Service Manual.
Automatic Timing Advance Does Not Operate Correctly
Check with engine warm. Use the 8T5300 Engine Timing Indicator Group and 8T5301 Diesel Timing Adapter Group. Special Instruction Form No. SEHS8580 has instructions and calibration procedures for this tool group. If the timing indicator group 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.
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 through the head adapter and crank the engine until fuel comes out. Tighten the fuel line nut. 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 through the head adapters 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 35 kPa (5 psi) of air pressure to the fuel tank.
| 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 leakage at the connections between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the line. 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.