The identification of air resistance phenomena under high-temperature engine conditions requires the combination of multi-dimensional parameter monitoring. The preferred diagnostic process is infrared temperature measurement: when the surface temperature of the fuel pipeline exceeds 65°C (ambient temperature > 35°C), the saturated vapor pressure of the fuel reaches 104kPa, exceeding the critical value of the pump suction force of 98kPa. At this time, the bubble generation rate can reach 200 per minute (with a diameter of 5μm). For instance, according to statistics from Dubai Taxi Company in 2022, 40% of Lexus LX570 breakdowns were caused by a peak temperature of 72°C in the fuel pipe near the intake manifold, which led to a 15-second instantaneous fuel supply interruption, with a median repair cost of 900 dirhams.
The body temperature of the Fuel Pump is the core indicator. Experiments have proved that when the pump body temperature rises to 60°C (the reference working limit is 55°C), the probability of internal fuel vaporization increases by 70%. At this time, if the measured fluctuation of the supply current exceeds ±1.5A (4.8A±0.3A under normal load), it can be determined that gas resistance has formed. BMW Technical Bulletin SIB 16 02 19 pointed out that after idling for 30 minutes, the oil pump resistance of the N52 engine jumped from 0.8Ω to 1.3Ω (an increase of 62.5%), directly causing the flow rate to drop sharply from 2.5L/min to 0.8L/min (a decrease of 68%).
OBD data stream analysis can quantify the influence of vapor lock. If the long-term fuel correction value (LTFT) suddenly increases from ±5% to ±20% and is accompanied by short-term correction (STFT) fluctuations of ±15% per second (normal value ±7%), the probability of failure exceeds 90%. In the case of the Ford F-150 5.0L model, the summer driving data record in an area at an altitude of 2,000 meters shows that when the intake air temperature is 51°C, the fuel rail pressure drops sharply from 350psi to 120psi (a decrease of 65.7%), and the frequency of ECU triggering fault codes P0191/P0087 increases by 300%.
Dynamic stress testing is the golden verification method. Connect the mechanical pressure gauge for a road test. When the fluctuation range of the oil rail pressure exceeds ±25psi (allowable value ±10psi) and the fluctuation frequency reaches 3Hz (normal 0.5Hz), it is a feature of air resistance. The recall report of Chrysler Pacifica hybrid models confirms that during tests on a 35°C slope, the pressure dropped from 42bar to 15bar within 7 seconds (below the minimum fuel supply threshold of 28bar), resulting in a 15% increase in the rate of power interruption accidents.
Economical alternative solutions include the transparent hose observation method: Install high-temperature resistant polyamide tubes (with a temperature resistance of 150°C) on the return oil pipe, and confirm air resistance when the bubble group density is visually greater than 50 per cm³. The Australian Cross-Country Association verified that the accuracy of this method reached 80% in a 45°C environment, and the implementation cost was only 15 US dollars (compared with 200 US dollars for the pressure gauge solution). However, it should be noted that the error rate of this method is ±10%, and it is not applicable to high-pressure direct injection systems.
The response strategy should integrate material upgrading and thermal management. Modifying the phenolic resin heat insulation cover can reduce the pump body temperature by 18°C (original data from Mercedes-Benz). Combined with the pulse oil pump controller (duty cycle 70% to 95%), the probability of cavitation occurrence can be reduced from 22% to 5%. The Nissan Patrol Car Club’s actual test proved that installing aluminum alloy heat sinks on the fuel guide rails (increasing the surface area by 300cm²) reduced the peak oil temperature from 74°C to 62°C (a decrease of 16.2%), and increased the engine’s thermal fade delay rate by 40%.