Cause Analysis of Isuzu Engine Failure

- Jul 31, 2020-

Cause Analysis of Isuzu Engine Failure

There are many reasons for the phenomenon of engine weakness, which can be summarized as the following aspects from the perspective of working principle and practice:

     1. Gas is blown into the oil circuit of the diesel fuel supply system, which reduces the amount of oil in the oil supply system, resulting in a small amount of oil in the high-pressure oil circuit.

     2. Engine injector is damaged, diesel is poorly atomized, and injector is dripping. According to past experience, the fuel injector drips oil. There are two possible reasons. One is because the high-pressure diesel fuel sprayed from the fuel injection system often entrains some mechanical impurities into the fuel injector when the engine is working. Attached to the sealing cone surface of the needle valve body to make it tightly sealed; second, due to the ablation of high-pressure and high-temperature gas in the combustion chamber, the frequent scouring of mechanical impurities during work combustion, the sealing ring between the needle valve and the needle valve body There will be pitting and corrosion pits on the surface, which will cause the deterioration of the sealing performance between the injector needle valve and the needle valve body and drip oil, which will cause poor combustion.

     3. Malfunction of diesel high pressure oil pump. The cylindrical pressure relief ring belt and the delivery valve seat have serious wear conditions, and the pressure relief belt and the upper end of the valve seat are ground into a conical shape, which makes the matching gap too large, so that the pressure relief belt will not be damaged when the fuel injection pump is working. All the valve seats are exposed and the oil pressure of the high-pressure oil pipe decreases. In order to increase the oil pressure in the oil pipe to the injection pressure during the second injection, it takes more fuel supply time, so the injection time lags behind. The amount is correspondingly reduced, so that when the high-pressure fuel pump stops supplying fuel, there is too much residual diesel in the high-pressure fuel pipe, and the remaining oil pressure is too high, so that the fuel injection nozzle is not simply sprayed and the phenomenon of back drip occurs.

     4. The cylinder pressure is too low. The reasons for the low cylinder pressure: the gaps of each piston ring are aligned and not staggered; the piston ring breaks and the cylinder pulls the cylinder; the valve spring suddenly breaks or the valve bites suddenly; the cylinder gasket is damaged. Insufficient pressure will inevitably emit a large amount of white diesel vapor or oil mist from the exhaust pipe, resulting in insufficient engine power.

     5. The fuel supply advance angle is too small. When assembling the engine, the timing gear mark and the high-pressure oil pump gear mark were not aligned, causing the high-pressure pump to supply oil too late.

     6. The cylinder gasket of the engine is eroded, the sealing is not tight, and the cooling water rushes into the cylinder, causing poor engine combustion.