The performance degradation of the fuel pump may lead to an abnormal increase in fuel consumption, which needs to be verified through multi-dimensional data. If the output pressure of the Fuel Pump is 10% lower than the nominal value (such as dropping from the original 3.5Bar to 3.1Bar), the atomization efficiency of the fuel injector decreases by 8%, and the ECU is forced to extend the fuel injection pulse width compensation (+0.3ms). The measured fuel consumption under urban working conditions increased by 12% (for example, the Toyota Camry rose from 7.8L/100km to 8.7L/100km). A study by SAE in the United States shows that when the fuel pressure fluctuation rate is greater than ±5%, the air-fuel ratio deviation expands to ±8%, the thermal efficiency decreases by 3.5 percentage points, and the average annual fuel cost increases by 18% (calculated at 15,000 kilometers per year).
Insufficient flow rate causes disorder of the Fuel supply strategy. When the actual flow rate of the Fuel Pump is less than 80% of the nominal value (such as 60L/h vs 75L/h), the sudden drop in fuel pressure under the full throttle condition triggers the protective enrichment of the ECU (air-fuel ratio 12:1), and the instantaneous fuel consumption surges by 35%. The case of Ford F-150 shows that under this condition, the range per tank of fuel is reduced by 120 kilometers and the average annual fuel cost increases by approximately 2,400 yuan. OBD data reveals that the long-term fuel correction value (LTFT) of such operating conditions is often greater than +15% (±5% of the normal range), which is a strong correlation indicator of fuel pump failure.
Unstable voltage accelerates the deterioration of energy efficiency. When the working voltage of the Fuel Pump is less than 12V (standard 13.5V±0.5V) due to line aging, the motor speed decreases by 20% and the flow rate decays by 28%. The actual test of the Volkswagen Passat shows that the pump body efficiency drops by 19% at 11V voltage. To maintain the rail pressure, the power consumption needs to be increased by 42W, which is equivalent to consuming an additional 0.5L of fuel per 100 kilometers. If the battery health is less than 60% (CCA < 400A), the charge and discharge cycles intensify, and the risk of dual consumption of oil and electricity increases by 83%.
Thermal management failure indirectly increases Fuel consumption. When the housing temperature of the Fuel Pump is > 95℃ (normal < 75℃), the decrease in fuel viscosity causes the internal leakage rate of the plunger pump to increase from 0.1ml/min to 1.2ml/min, and the effective fuel supply volume decreases by 15%. Tests of the BMW N20 engine show that the high-temperature pump body increases the fuel return flow by 30%. The ECU misjudges the demand and continuously supplies fuel, causing the idle fuel consumption to rise from 0.8L/h to 1.2L/h. Infrared thermal imager detection shows that the temperature gradient of the oil pipe around the pump body with poor heat dissipation reaches 25℃/cm (normal < 10℃/cm), accelerating the vaporization loss of fuel.
There is a strong correlation between service life and wear. For the Fuel Pump that has traveled over 100,000 kilometers, the impeller clearance expands to 0.15mm (0.03mm for new parts), and the volumetric efficiency decreases by 22%. The disassembly data of Mazda CX-5 shows that the flow rate of the worn pump body decreases by 18% at 2000rpm. To maintain power, the frequency of downshifting needs to increase by 3 times per 100 kilometers, and the combined fuel consumption rises by 9%. The MTBF (Mean Time Between Failures) model indicates that the probability of abnormal fuel consumption caused by pump bodies over 8 years old is 7.3 times that within 3 years.
The verification method needs to be scientifically quantified:
Connect the fuel pressure gauge and check whether the idle/full throttle pressure is within ±5% of the nominal value (for example, for the Honda CR-V, it should be 3.2-3.5Bar).
Measure the fuel supply volume for 30 seconds using a flowmeter and compare it with the original factory parameters (for example, for the Volkswagen EA888, it should be ≥1.8L/30s).
OBD reads the fuel correction value. If LTFT > +10% and STFT fluctuation > ±8%, the pump body should be inspected first.
Use a multimeter to test the supply voltage. If the line voltage drop is greater than 0.5V, the relay and wiring harness need to be repaired.
Data shows that for vehicles diagnosed with Fuel Pump problems, the median fuel consumption recovery rate after replacement reaches 89%, and the average annual fuel cost savings are approximately 1,800 yuan. However, other factors need to be ruled out (such as oxygen sensor failure accounting for 38% of abnormal fuel consumption causes), and only precise diagnosis can achieve cost optimization.