發動機燃燒室內可燃混合氣濃度過低，會造成發動機動力不足、污染排放超標，以及積炭增加等一系列問題，有時發動機故障燈也會點亮。導致可燃混合氣濃度不正確的原因有哪些呢?
下面我們就一起來看檢修思路。
故障檢修與診斷
該車配備了渦輪增壓發動機和高壓油泵，查看故障出現時的凍結幀，看到高壓燃油的壓力資料低於參考值，且當時發動機正處於負荷較高的工況。連接燃油表，起動發動機，急速時的燃油壓力符合標準。
進行路試，中低速行駛時沒有出現故障警告，高壓燃油資料符合標準。但在進入高速行駛之後，儀錶板上出現了故障警告，此時的高壓燃油壓力低於標準。從上述測試結果推斷，發動機在高功率輸出時沒有得到充足的燃油供應，可能的故障點包括燃油泵供油不足、燃油濾清器堵塞以及高壓油泵在發動機高功率輸出時出現泄壓。
故障排除
與車主溝通得知，車輛不久前剛更換過燃油濾清器。通常來說，新燃油濾清器出現堵塞的可能性不大但在查看該車匹配的燃油濾清器型號時，維修人員發現一個細節，該車型燃油濾清器有兩種配置.
這款車的發動機有高低功率版本之分，對應的燃油濾清器型號不同，其能承受的壓力也不一樣。但這些燃油濾清器的外觀形狀相同，如果不注意很容易裝錯。高功率燃油濾清器外殼上印有“6.6 Bar”字樣，而在低功率燃油濾清器上，這個數字是“4.0 Bar”
如果給高功率車型安裝低功率的燃油濾清器，在發動機高負荷運轉時，燃油泵輸出的壓力就會使燃油濾清器泄壓，導致發動機動力不足，出現混合氣過稀的故障記錄，發動機故障燈點亮。
舉升車輛檢查燃油濾清器，外觀比較新，但燃油濾清器外殼上並沒有刻印品牌和零件號，懷疑是劣質產品。此類劣質燃油濾清器，恐怕在生產環節就沒有“區分高低壓”的概念，也直接引發了故障,更換對應型號的高功率版燃油濾，隨後再次外出路試，故障不再出現，高壓燃油壓力資料始終正常，故障排除。
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A low concentration of combustible mixture in the combustion chamber of an engine can cause a range of problems such as lack of engine power, excessive pollution emissions and increased carbon build-up, and sometimes the engine fault light will come on.
What are the causes of incorrect combustible mixture concentration? Let's look at the following inspection ideas
Troubleshooting and diagnosis
The vehicle is equipped with a turbocharged engine and a high pressure fuel pump. When looking at the freeze frame at the time of the fault, the high pressure fuel pressure data was lower than the reference value and the engine was under high load. Connect the fuel gauge, start the engine and the fuel pressure at high speed is within the standard
During the road test, there was no fault warning at low and medium speeds and the high pressure fuel data was in line with the standard. However, after entering high speed, a fault warning appeared on the dashboard and the high pressure fuel pressure was below standard at this time. From the above test results, it can be deduced that the engine is not receiving sufficient fuel supply at high power output. Possible fault points include insufficient fuel supply to the fuel pump, clogged fuel filter and pressure relief from the high pressure fuel pump at high power output of the engine.
Troubleshooting
Talk to the owner and find out that the vehicle has recently had its fuel filter replaced. Normally, a new fuel filter is unlikely to be clogged, but when looking at the matching fuel filter model of the car, the mechanic found a detail that the car had two configurations of fuel filters.
This car has a high and low power version of the engine and the corresponding fuel filters are different and can withstand different pressures. However, these fuel filters are identical in appearance and can easily be fitted incorrectly if care is not taken. The high power fuel filter has the word "6.6 Bar" printed on the housing, whereas on the low power fuel filter the number is "4.0 Bar".
If a low-powered fuel filter is fitted to a high-powered model, the fuel pump pressure will drain the fuel filter when the engine is running under high load, causing the engine to be underpowered and a lean mixture fault to be recorded and the engine fault light to illuminate.
The fuel filter was relatively new in appearance, but there was no brand or part number engraved on the fuel filter casing, so it was suspected to be an inferior product. This kind of inferior fuel filter, I am afraid that in the production link there is no "distinguish between high and low pressure" concept, but also directly caused the fault, replace the corresponding model of high power version of the fuel filter, then again outside the road test, the fault no longer appears, high pressure fuel pressure data is always normal, the fault is eliminated.
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