康明斯发动机动力不足常见故障判断与排除

一、康明斯柴油发动机动力不足的现象与原因分析 

　　柴油发动机的工作过程经历进气、压缩、作功、排气四个行程。柴油机在进气行程中吸入的是纯空气;在压缩行程接近终了时，气缸内空气压力可达3.5～4.5MPa、温度高达750～1000K，同时，柴油经喷油泵将油压提高到10MPa以上，通过喷油器喷入气缸，在很短时间内与空气混合后便立即自行发火燃烧。在高压气体推动下，活塞向下运动并带动曲轴旋转而作功，废气同样经排气管排入大气中。

　　康明斯发动机与传统柴油机最大的不同是采用了PT喷油器，即是将传统燃油泵的柱塞(产生高压)与喷油器针阀(控制喷射)集成为一体，取消了高压油管，有效地消除了在高压和高速下供油的压力波动对供油规律的影响，而且有更高的喷油压力(60～150MPa，甚至更高)，不仅可以满足强化发动机所需的高喷油压力和高喷射速率，而且雾化好、充气效率高，更有利于燃烧和提高发动机性能。

 

　　发动机动力不足，从理论上讲，主要是由于气缸内混合气燃烧不良或发动机运动机件摩擦阻力过大。导致燃烧不良的原因很多，例如:燃油供应不足、雾化不良，供油提前角不准、气缸密封性下降、进气不足、排气不畅或配气相位失准等。摩擦阻力过大的原因主要是发动机运动机件的间隙过小或润滑油供应不足。

　　发动机动力不足且连续排黑烟，是发动机大多数缸或所有的缸均供油量过多、燃油与空气混合比例失调、燃烧时严重缺氧、柴油燃烧不完全，悬浮游离状的碳元素随废气一同排出而形成的。若排气管是断续排黑烟，且伴有“突突”声，说明个别缸燃烧不完全。

主要原因为:

①喷油泵调试不当，使供油量过多，燃烧不完全。

②多数喷油器的喷射质量差。

③供油不正时。

④进气门开启高度降低、开启时间推迟，导致进气不足。

⑤空气滤清器滤芯过脏或空气滤清器安装有误，使空气不流畅。

⑥增压器的增压效能下降。

⑦燃油质量过差。

 

　　发动机运转不均匀，排气管大量排白烟、高速运转不良、加速不灵敏，而且温度易过高，主要的原因则有:喷油提前角过小、喷油器雾化不良、发动机温度过低、气缸内有水或油中有水等。

二、康明斯柴油发动机动力不足的故障诊断与处理方法 

　　诊断此类故障时，应从故障特征最明显处着手，遵循由表及里、先易后难、少拆为益的基本原则。

　　1．排气管排黑烟 

　　(1)若发动机突然冒黑烟，但运行一段时间后故障自然消失，则多为燃油质量较差所致，由于油中的杂质堵塞喷油器致喷射质量差，排气冒黑烟，运行一段时间后杂质被高压油冲掉，此种故障不用处理。

　　(2)若连续排黑烟，可考虑检查进气是否通畅、进气管是否变形增加了进气阻力。先拆下空气滤清器盖，取出滤芯并清理维护后重新试机，观察排气管是否仍继续排黑烟。如果排烟明显减少，则说明是空气滤清器过脏或安装有问题，影响了进气量，应加强对进气系统的维护保养。

　　(3)若进气道气流通畅，则应检查供油时间是否过迟，供油过迟会使进入气缸的燃油来不及充分燃烧就被排出而形成黑烟。

　　(4)多数喷油器的喷射质量严重恶化，燃油雾化差，不能适应燃烧室形状的需要，致使可燃混合气形成困难，部分燃油转化成游离碳被排出，这也是导致黑烟的原因之一，故也应对喷油器进行检查修理。

　　(5)检查燃油质量是否合乎标准，应使用符合发动机在该地区环境温度下正常工作的标准柴油。

　　(6)检查增压器的工作是否正常。当增压器失效时，发动机进气终了的压力下降，致使压缩终了温度、压力均下降，影响燃油的喷射雾化和燃烧温度。

　　(7)如喷油泵维修时间不长、排气管排黑烟，则应考虑是否喷油泵调试不当使供油量过多，对此应重新校正喷油泵在各种工况下的供油量，使之符合规定。

　　(8)若上述均正常，且发动机已运行了很长时间，可考虑检查气门开启的高度和开启时间是否正确。长时间的使用可使气门传动机件磨损，正常的配气相位和气门升程失准，进气量减少，缸内残余废气量相应增加，直接影响燃油的充分燃烧。

　　(9)对于转速不均、断续排黑烟、发动机无力的诊断可采用逐缸断油法检查。当某缸断油时，发动机转速明显降低，黑烟减少，异响也消失，则说明该缸供油量过多，应对该缸喷油量进行检查调整。若发动机转速变化较小，黑烟消失，则说明该缸喷油器喷雾质量差，应对该喷油器进行检查维修。若发动机转速仍无变化，则说明该缸不工作，应检查该缸的高压供油情况，对PT喷油器进行检查和调整。

　　2．排气管排白烟 

　　(1)发动机动力不足，排气管排灰白烟雾，首先将手靠于消声器排气口处，如果手上留有水珠，则应检查柴油中和气缸内有无水分。

　　(2)发动机刚发动时冒灰白烟，起因是起动时温度过低，部分柴油挥发成蒸汽，未经燃烧直接排出所致。若待发动机温度升高后灰白烟逐渐消失，则属正常现象。若发动机刚起动时冒灰白烟，且温度升高后冒黑烟，则说明气缸压力不足，虽然压燃条件有所改善，但柴油仍不能完全燃烧，使发动机动力不足，应对气缸压力进行检查维修。

　　(3)发动机动力不足，排气管排灰白色烟雾，通常是喷油提前角过小或喷油器雾化质量不佳所致。若伴随发动机温度过高、提速缓慢的情况，则可认为是喷油时间过迟，否则是喷油器雾化质量不佳。由于康明斯发动机采用的是PT喷油器，将传统燃油泵的柱塞与喷油器针阀集成为一体，因此无论喷油时间过迟还是喷油器雾化质量不佳都要对PT喷油器进行调整。

Cummins engine underpowered common fault judgment and exclusion
A Cummins diesel engine power shortage cause analysis
The working process of the diesel engine has experienced an intake, compression, for power, exhaust four stroke. Diesel pure air sucked in the intake stroke; in the compression stroke near the end of the cylinder, the air pressure of up to 3.5 ~ 4.5MPa, ~~ 1000K temperature up to 750, Meanwhile, the diesel fuel by the fuel injection pump hydraulic raise to more than 10MPa injected into the cylinder through the injector itself immediately after a very short period of time is mixed with air pyrophoric combustion. Driven by high-pressure gas piston downward movement and driven by the crankshaft rotation for power, the exhaust gas is the same through the exhaust pipe into the atmosphere.
Cummins Engine with traditional diesel engine is the biggest difference PT injector that is traditional fuel pump plunger (to generate high pressure) and injector needle (control injection) are integrated, and the abolition of the high pressure tubing, effectively eliminate the influence of high pressure and high speed oil supply pressure fluctuations on the oil law, but higher injection pressure (60 ~ 150MPa, or even higher), not only meet the the enhanced engine required high injection pressure and high injection rate, and atomization, volumetric efficiency is high, is more conducive to the combustion and improve engine performance.
Lack of engine power, in theory, primarily due to the poor combustion gas mixture within the cylinder or the engine moving parts, the frictional resistance is too large. Many reasons lead to poor combustion example: fuel supply shortage, poor atomization, fuel supply advance angle are not allowed to cylinder sealing decline, inadequate intake, poor exhaust valve timing inaccuracy. Excessive frictional resistance mainly due to the moving parts of the engine the gap is too small or inadequate supply of such oil.
Lack of engine power, and continuous row of black smoke, the engine most cylinder or cylinder excessive oil, severe hypoxia imbalance of the fuel and air mixture, combustion, diesel combustion incomplete, suspended free-shaped carbon element with the The exhaust gas discharged together formed. If the exhaust pipe is intermittent row of black smoke, and accompanied by "chug" sound, indicating that the individual cylinder combustion is incomplete. The main reason for that: ① injection pump debugging properly, so that the excessive amount of oil, incomplete combustion. ② the majority of the injector injection of poor quality. ③ oil supply is not correct. (4) the intake valve opening height decreased postpone the turn-on time, leading to inadequate intake. (5) air cleaner element too dirty air filter is installed incorrectly, so that the air is not smooth. ⑥ turbocharger supercharging performance drop. ⑦ fuel quality is too poor.
Engine running unevenly, exhaust pipe a large number of rows of white smoke, poor high-speed operation and acceleration insensitive, and easy too high temperature, the main reasons are: injection advance angle is too small, poor atomization of the fuel injector, the engine temperature is too low, within the cylinder, water or oil, water and the like.
Cummins diesel engine power failure diagnostic and treatment methods
Diagnosis of such failure, proceed should be the most obvious fault feature, follow the outside to the inside, the easier issues first, less demolition for the benefit of basic principles.
1. Exhaust pipe smoky
(1) If the engine suddenly black smoke, but running for some time after the fault disappears naturally, is more due to poor fuel quality, due to impurities in the oil clogged injector caused by the poor quality of jet black smoke exhaust run after a period of high pressure oil impurities are washed away, do not have to deal with such a failure.
(2) If a continuous row of black smoke, consider check intake patency and whether the intake pipe deformation increased intake resistance. Remove the air filter cover, remove the filter and clean the machine re-test after maintenance and observation continue smoky exhaust pipe. If the smoke is significantly reduced, the air filter is too dirty or installation problems, affecting the feed rate, should strengthen the maintenance of the intake system.
(3) If the inlet air to flow freely, you should check whether the injection time with late, too late to fully burn oil too late to make the fuel into the cylinder to be discharged and the formation of black smoke.
(4) serious deterioration in the quality of most injector spray fuel atomization, can not meet the needs of the combustion chamber shape, resulting in a combustible mixture formation difficult part of the fuel is discharged into free carbon, which also contributed to the reason of black smoke a fuel injection, it should also inspect repairs.
(5) Check the fuel quality standard, and should be used in line with the engine at the ambient temperature of the area under the normal work standard diesel.
(6) Check the turbocharger is working properly. When the failure of the turbocharger, the end of the engine intake pressure is decreased, resulting in the compression end temperature, pressure drop, and to affect the fuel spray atomization and combustion temperature.
(7) injection pump repair time is not long, smoky exhaust pipe, you should consider whether the injection pump debugging improper excessive oil, this should be recalibrated fuel injection pump in the amount of oil under various conditions compliance.
(8) If the above normal, and the engine has been running for a long time, could be considered the correct check valve opening height and open time. The long period of use allows the valve train engine wear and misalignment normal valve timing and the valve lift, intake air amount reducing cylinder corresponding increase in the amount of residual gas, and directly affect the full combustion of the fuel.
(9) For speed uneven, intermittent row of black smoke check off the oil law-by-cylinder engine unable to be used for diagnosis. When a cylinder off oil, engine speed decreased significantly reduce black smoke, abnormal noise disappeared, the cylinder oil excessive checks adjustment to cope with the cylinder fuel injection quantity. If the engine speed changes, black smoke disappeared, the poor quality of the cylinder injector spray respond to the injector for inspection. If the engine speed remained unchanged, the cylinder does not work, you should check the high pressure fuel supply situation in the cylinder, check and adjust the PT injector.
2. Row of white smoke exhaust pipe
(1) the lack of engine power, exhaust pipe row of gray smoke, first hand against the muffler exhaust port at the hands left drops of water, you should check whether the water in the diesel and cylinder.
(2) when the engine has just launched to take gray smoke, causes the starter when the temperature is too low, some diesel volatile steam without burning directly discharged due. Gray smoke gradually disappear until the engine temperature is elevated, it is a normal phenomenon. If the engine is just starting to take gray smoke, black smoke and the temperature rises, the cylinder pressure, compression ignition conditions improved, but the diesel is still not complete combustion, the engine is underpowered, and respond to the cylinder pressure checks and maintenance .
(3) the lack of engine power, exhaust pipe row of gray-white smoke is usually fuel injection advance angle is too small or injector atomization due to poor quality. Accompanied by excessive engine temperature, slow speed, you can think is the injector too late, otherwise poor quality fuel injector atomization. Cummins Engine PT injector is integration, the traditional fuel pump plunger injector needle as a whole, regardless of injection time is too late or injector atomization quality is poor PT injector must carried adjustment.