EXHAUST SMOKE ANALYSIS
1. High exhaust-back pressure or a restricted air inlet causes insufficient air for combustion and will result in
incompletely burned fuel.
High exhaust-back pressure is caused by faulty exhaust piping or muffler obstruction and is measured at the
exhaust manifold outlet with a manometer. Replace faulty parts.
Restricted air inlet to the engine cylinders is caused by clogged cylinder liner ports, air cleaner or blower air
inlet screen. Clean these items. Check the emergency stop to make sure that it is completely open and
readjust it if necessary.
2. If the engine is equipped with a throttle delay, check for the proper setting, leaky check valve and restricted
filling of the piston cavity with oil from the reservoir.
If the engine is equipped with a fuel modulator, check the cam to determine if it is stuck in the full-fuel posi-
tion. Verify tightness of the roller lever clamp on the control tube. Determine correctness of the installed fuel-
modulator piston spring and check if the spring has taken a permanent set, or if the spring rate is too low.
Check for improperly timed injectors and improperly positioned injector rack control levers. Time the fuel
injectors and perform the appropriate governor tune-up.
Replace faulty injectors if this condition still persists after timing the injectors and performing the engine tune-
Avoid lugging the engine as this will cause incomplete combustion.
3. Check for use of an improper grade of fuel. Refer to Fuel and Oil Specifications.
4. Check for internal lubricating oil leaks and refer to the High Lubricating Oil Consumption chart.
5. Check for faulty injectors and replace as necessary.
Check for low compression and consult the Hard Starting chart.
The use of low-cetane fuel will cause this condition. Refer to Fuel and Oil Specifications.