The fuel supply of the high-pressure fuel pump is precisely calculated and set by the manufacturer based on engine combustion efficiency, emission requirements, etc. Any arbitrary adjustment will break the precise balance of the fuel system and cause a series of serious consequences:
1、 Abnormal engine performance
Power output disorder
Fuel supply increase: Excessive fuel injection leads to incomplete combustion, and unburned fuel accumulates in the combustion chamber, which may cause "detonation" or "premature combustion", resulting in severe engine shaking, power drop, and even piston and valve erosion.
Reduce fuel supply: Insufficient fuel supply can lead to a lean mixture in the cylinder, insufficient engine power, weak acceleration, and possible "stalling" during heavy loads.
Deterioration of fuel economy
Deviation of fuel supply from the original factory set value can cause an imbalance in the air-fuel ratio (air to fuel ratio). For example, the optimal air-fuel ratio for an electronically controlled high-pressure fuel pump in a diesel engine is approximately 14.7:1. Increasing the fuel supply will cause the air-fuel ratio to be lower than this value, resulting in incomplete fuel combustion and an increase in fuel consumption by 15% -30%.
2、 Excessive emissions and damage to the post-treatment system
Uncontrolled emission of pollutants
When the fuel supply is too high, the nitrogen oxides (NOx) and particulate matter (PM) produced by fuel combustion will increase significantly, directly leading to vehicle emissions exceeding the standard and failing annual inspections.
For National VI vehicles equipped with DPF (particulate matter filter) and SCR (selective catalytic reduction system), excessive combustion of fuel can accelerate DPF blockage and damage the SCR catalyst due to abnormal exhaust temperature, with repair costs reaching thousands of yuan.
Post processing system chain failure
Abnormal fuel supply can trigger a fault alarm in the ECU (engine control unit), forcing it to enter "limp mode" (limiting power output), and may also misjudge post-processing system faults, resulting in unnecessary component replacement.
3、 The lifespan of high-pressure fuel pumps and injectors is shortened
The internal wear and tear of the oil pump has intensified
Increasing the fuel supply requires the oil pump to output higher pressure (such as increasing the pressure of the common rail system from 1600bar to above 1800bar). Exceeding the design load will accelerate the wear of precision components such as plungers and oil outlet valves, resulting in internal leakage and decreased pressure holding capacity of the oil pump. Ultimately, the oil pump needs to be replaced as a whole (at a cost of approximately 2000-5000 yuan).
Abnormal damage to the fuel injector
Fluctuations in fuel supply can cause the injector to frequently operate in an over flow state, causing the nozzle needle valve to become stuck and worn due to excessive oil pressure, resulting in dripping or poor atomization. For example, the rated flow rate of Bosch CRIN series injectors is 200ml/30s, and forcibly increasing it to 250ml/30s will increase the needle valve wear rate by 2-3 times.
4、 ECU data disorder and security risks
Control system misjudgment
The fuel supply of the high-pressure fuel pump is strictly matched with the preset parameters of the ECU, such as injection pulse width and rail pressure. Random adjustment can result in actual fuel quantity not matching the ECU command, causing "rail pressure too high/too low" fault codes, and even burning the ECU circuit board (with repair costs exceeding a thousand yuan).
Risk of fuel leakage
Increasing the fuel supply may cause the pressure in the fuel pipeline to exceed the design limit (such as a low-pressure fuel pipe with a pressure resistance of 5 bar, increasing the pressure to 7 bar), resulting in rubber pipeline rupture, joint oil leakage, and the possibility of spontaneous combustion in high temperature environments.
5、 Suggestions for correct operation
Non professional adjustments are strictly prohibited: The fuel supply of the high-pressure oil pump must be read through a dedicated diagnostic device (such as the Bosch EDC17 system that requires a VCI diagnostic instrument) to accurately calibrate the data stream based on the engine operating conditions. Unauthorized personnel are not authorized to modify parameters.
Priority principle for troubleshooting: If there is suspicion of abnormal fuel supply, it is necessary to first check whether the fuel pressure sensor, rail pressure regulator (PCV valve) and other components are damaged, rather than directly adjusting the fuel supply.
Relying on original factory technology: When it comes to adjusting oil pump parameters, it is necessary to contact the manufacturer's after-sales or professional maintenance station and use original factory software for calibration (such as matching oil pump data with Insite software for Cummins QSB engines).
Summary: The fuel supply of the high-pressure fuel pump is the "core parameter" of the fuel system. Adjusting it arbitrarily is like "tampering with the DNA of the engine", which not only causes performance, emissions, and lifespan issues, but may also lead to safety risks. When repairing, it is necessary to follow the principle of "data first, professional operation" to avoid irreversible damage caused by blind adjustments.
