How to Diagnose The Power Failure of Single Pump Diesel Engine?

The fault diagnosis method for insufficient power of a single pump diesel generator is different from other types of diesel engines and has certain uniqueness and originality. Taking the example of the Daidz BFM1013 single pump diesel generator, a brief explanation is as follows:

(1) Speed detection. Check the maximum idle speed with a tachometer. According to the different configurations of diesel engines, the maximum idle speed should be 6% -8% higher than the rated speed; Calculation formula: maximum idle speed=rated speed xl.07r/min; If the maximum idle speed is not enough, check if the high-speed limit screw is not set enough and adjust it accordingly.

(2) Check the fuel injectors. Are there any leaks or defects such as pitting caused by insufficient primary oil circuit pressure.

(3) Check the low-pressure oil circuit system of the diesel generator. Insufficient low-pressure oil circuit pressure can directly lead to insufficient power and injector cavitation.

The pressure detection point of the low-pressure oil circuit of the diesel generator should be located behind the oil outlet of the fine filter (i.e. the oil inlet of the crankcase). If there is no measurement space at this location, it can be measured in front of the return oil valve (i.e. at the outlet of the crankcase).

Attention: At the rated speed, the pressure measured at the outlet of the crankcase should be about 0.01MPa lower than the pressure at the inlet of the crankcase.

The following factors may be the cause of insufficient low-pressure oil circuit pressure: 1. Whether the fuel primary or secondary filter is blocked; 2. Is the oil return overflow valve damaged; 3. Is there excessive flow resistance in the oil pipeline from the fuel tank to the oil pump; 4. Can the oil pump provide sufficient oil supply pressure; 5. Is there too much flow resistance in the return oil pipeline from the return oil overflow valve to the fuel tank? If this resistance is too high, the return oil quantity is insufficient and the fuel temperature will increase (the fuel temperature should not exceed 80 ℃). If the fuel pre pressure is insufficient while ensuring that the filter element is not clogged, the return oil relief valve should be inspected or replaced.

If the pressure is still insufficient, the entire oil pipeline should be checked for excessive flow resistance: directly use an oil barrel to supply oil in front of the oil pump, so as to determine whether the resistance is caused by the original factory equipped oil supply pipeline from the tank to the oil pump and the diesel coarse filter element. The inner diameter of the oil pipe in front of the fuel pump should not be less than 12mm, and the fuel pressure at the inlet of the fuel pump at high idle should be greater than -0.O5MPa. For diesel engines that meet Euro II emissions, it should be greater than -0.035MPa.

If the pressure is still insufficient, the return oil volume should be checked: remove the return oil end of the return oil pipe from the tank and directly insert it into an empty bucket. Measure the return oil volume of the diesel engine at high speed without load within 1 minute, which should be above 8L.

(4) Check the boost air pressure and exhaust temperature at full load. Only when the speed drops from the highest idle speed to the rated speed, can the output power of the diesel engine reach full load. At full load, the boost pressure in the intake manifold should reach at least 0.13MPa, and the exhaust temperature (measured at a point 100mm behind the turbocharger) should be between 450 ℃ and 480 ℃. The methods for measuring boost pressure are divided into static measurement and dynamic measurement. Static measurement value: 0.5MPa; Dynamic measurement value: 0.13-0.15MPa. If the fuel supply is sufficient but the boost pressure is still insufficient, the exhaust back pressure should be checked and should not exceed 4.9kPa.

(5) Check the exhaust brake assist system. If the vehicle (diesel engine) is equipped with an exhaust brake assist system, the internal valve position of the exhaust brake valve should be checked. If approaching the semi closed state, it will cause poor exhaust of the diesel engine, which will affect the speed of the turbocharger and cause insufficient intake, ultimately leading to insufficient diesel power.

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