Clogging of the Fuel Pump and Misfire of the engine have a very strong relationship. Tests show that if the clogging rate of the fuel filter is above 30% (for example, if the pore size is reduced from 50 microns to 35 microns), the fuel supply pressure will fall from 50 psi to 38 psi, the fuel injector flow error rate will rise from ±2% to ±8%, and the probability of the air-fuel ratio (AFR) being off the ideal ratio (14.7:1) will be 45% greater. For instance, in 2020, the Honda Accord was complained about for misignition due to a clogged fuel pump filter. OBD information showed that the short-term fuel correction value (STFT) of the defective vehicle fluctuated by ±25% (usually ±10%), and the misignition rate jumped drastically from 0.1 times per minute to 4.2 times per minute. After the recall, the pump body was replaced and the rate of misignition reduced by 92% (Data source:) NHTSA Recall Report.
Restrictions in flow destabilize combustion directly. If the fuel output flow rate of the Fuel Pump is reduced from 5 L/min to 3.2 L/min (attenuation of 36%), then the fuel injection pulse width must be raised by 40% in high load conditions. Yet, ECU regulation lag can make the single-cylinder mixture concentration differ by ±5%, leading to cyclical fire failure. From SAE’s study in 2022, if the flow rate decreases by 70% of its rated value, underignition probability of turbocharged engines (like the Volkswagen EA888) at 3000 RPM rises from 0.5% to 12%, and the false alarm rate of the knock sensor tribles. A typical example is that user experience from BMW B48 engine shows that after a blockage at a local fuel pump, fire failure probability concentrated in the 3/4 cylinder is 68% (due to the pressure gradient difference at the fuel rail end).
The existence of impurities aggravates circuit and machinery failure. If the water percentage in the Fuel exceeds 0.1% or the particulate matter concentration is over 50 mg/L, the Fuel Pump impeller wear rate increases by 200%, causing A dynamic balance deviation greater than 0.8g·cm, thus resulting in motor current oscillations (from 5A±0.3A to 5A±1.5A). Ford’s 2021 research found that vehicles using low-grade ethanol fuel (E15) were four times more likely to accumulate metal particles from fuel pump rust plugging the fuel injector filter than those using conventional gasoline, and the cost of a misfire fault repair increased from $300 to $1,200 (fuel injector replacement). Furthermore, internal rust of the pump casing will increase the resistance value (e.g., from 2Ω to 5Ω), reduce the motor power by 30%, increase the range of fluctuation of fuel pressure to ±12 psi, and increase the rate of fire failure to 8 times per minute for cold start.
Diagnostic data are able to quantify the impact of congestion. Carefully monitored by the fuel pressure sensor, when the median pressure at idle speed is less than 40 psi (factory setting is 50-60 psi) and the Variance is more than 1.5, the prediction accuracy rate for the misfire risk model is as high as 89%. User data of 2022 Toyota Camry reveal that below 45 psi pressures, the rate of second cylinder misignition is 2.3 times greater compared to other cylinders, causing insufficient fuel delivery towards the end due to the variation in the oil rail length. Moreover, when fault codes OBD-II P0300 (random flame failure) and P0171 (system shortage) appear together, there is more than a 65% chance that fuel pump clogging exists (source of data: Bosch Diagnostic Manual).
Risk to safety should be weighed against economic risk. The cost of cleaning one fuel pump is roughly 50 to 100 US dollars. But if damage is caused to the fuel injector due to clogging, repair will be enhanced to 400 to 800 US dollars. According to the J.D. Power 2023 report, frequent replacement of the fuel filter (every 30,000 kilometers/2 years, at $30) can reduce the underignition failure rate by 72% and save the average amount of around $220 in yearly maintenance. Industry instances show that after General Motors changed its fuel pump filter from an unspecified to a 10-micron precision in 2021, its underignition warranty claims fell by 41%, recovering an annual expense of 18 million US dollars directly.
Technological development promotes congestion early warning. Bosch’s 2023 smart Fuel Pump uses pressure and flow sensors to calculate the pressure difference (ΔP) of the filter screen in real time. When ΔP exceeds 2 psi, it triggers a warning with a precision of up to 95%. The tests show that this technology has raised the MTBF (Mean Time Between Failures) of underfire faults from 150,000 kilometers to 220,000 kilometers, reducing users’ maintenance costs by 35%. They have been described as factory equipment on high-end models by companies like Audi and Mercedes-Benz, in a clear affirmation of the inherent value of preventive maintenance to the management of the risk of underignition.