We take forklift diesel engine as an example

  • Why does the engine emit blue smoke?

The reason for the blue smoke emission is that there is an excess of oil burning in the combustion chamber. The reasons for this phenomenon and how to eliminate it are as follows：

  1.  The oil sump is overloaded with oil, too much oil will splash to the cylinder wall with the high-speed crankshaft and run into the combustion chamber. The way to get rid of it is to stop for 10 minutes, check the oil dipstick and drain the excess oil.
  2. The cylinder liner piston ring set is badly worn resulting in excessive clearance, this causes oil to escape into the combustion chamber for combustion, while crankcase exhaust gases increase. The treatment is to replace worn parts in time.
  3. The piston ring is out of action. If the piston ring does not have enough elasticity, is stuck in the ring groove by carbon, or the ring mouth is in the same straight line, or the oil ring return hole is blocked If the piston ring is stuck in the ring groove, or the ring mouth is in the same line, or the oil ring return hole is blocked, it will lead to the oil entering the combustion chamber and the phenomenon of blue smoke. This is done by removing the piston rings, removing the carbon deposits, rearranging the ring fasteners and, if necessary, replace the piston cylinder kit.
  4. Excessive valve and guide clearance. A large amount of oil enters the combustion chamber inside the rocker arm during air intake and burns. This can be dealt with by promptly replacing worn valves and guides.
  5. Emissions of blue smoke and other reasons such as oil is too thin, oil pressure is too high, the engine is not well broken in, will cause oil combustion and blue smoke.

  • Why does the engine emit black smoke?

The phenomenon is due to incomplete combustion of fuel and generated. When black smoke is produced, it is often accompanied by a drop in engine power, high exhaust temperatures and high water temperatures, which This leads to wear and tear of several engine parts and affects engine life. The causes and troubleshooting methods for this phenomenon are as follows:

  1. Insufficient air intake or blocked air intake pipe. In order to find out the cause the following checks should be carried out: whether the air filter is blocked; whether the air intake pipe is leaking; whether the turbocharger is damaged.
  2. Improperly adjusted valve clearance Poor contact with the valve seal ring band. Valve clearance, valve springs and valve oil seals should be checked.
  3. The supply of each cylinder of the high pressure oil pump is uneven or too large. This leads to unstable speed and intermittent black smoke, which should be adjusted to make it balanced or within the specified range.
  4. The injection advance angle should be adjusted if the oil is injected too late.
  5. Poorly working or damaged fuel injectors should be removed for servicing.
  6. The cylinder liner and piston ring assembly are badly worn. When this situation occurs, the piston ring seal is not tight, the air pressure in the cylinder drops, resulting in the diesel engine can not fully combustion and black smoke, The engine power drops drastically and in severe cases the engine will stall automatically under load.

  • Why does the engine emit yellow smoke?

The yellow smoke is emitted at the medium speed stage at the beginning of the start-up period, and gradually decreases or disappears when the temperature rises or the load increases. It is easy to stall at idle speed Fire, body shaking, simultaneous air intake “choking”, lack of power and difficult starting, the reasons for this phenomenon and the methods of elimination are as follows Below.

  1. The individual intake and exhaust valves are not closed tightly, or the valve springs are not sufficiently elastic, the valve push rod is bent, and the intake and exhaust valves are ablated. The treatment is; grind the valves valves, remove carbon and replace worn parts.
  2. Excessive clearance between camshaft journal and seat bore or misalignment of air distribution phase, ablation of most valves, the cylinder liner and piston ring are excessively worn, the treatment is; adjust the clearance and replace the worn parts.