There are several reasons for the pressure drop: Mechanical wear, fuel contamination and system leaks. Fuel pumps have seals, bearings and impellers that wear out over time, particularly in high-pressure systems that operate at 60 PSI or higher. Such wear decreases the pump’s ability to maintain peak pressure, causing a slow performance degradation that can eventually strangle the engine’s horsepower.
Debris or contamination from fuel impurities (especially for older vehicles) will clog filters, inhibit flow, and create pressure drops. Industry data suggests nearly 30% of all fuel pump failures are due to fuel contamination. These problems are only compounded with the use of ethanol-blended fuels, as proven with the fact that ethanol also absorbs water, thus increasing the chances of corrosion and other internal damage. Ethanol can break down rubber and plastic seals and gaskets within fuel systems built for pure gasoline, hastening degradation in vehicles not “flex-fuel”-compatible.
Another cause of loss of fuel pressure is leaking in the fuel lines or bad connection. Cracks in a fuel line and bad fitting cannot maintain proper pressure in the system. In fact, as automotive expert Richard Bell points out, “A small leak can transform a well-designed, well-functioning fuel system into a performance nightmare,” which emphasizes just how vital it is for each and every fuel system to be completely airtight. If left alone to fester, these little leaks can turn into costly repairs, so regular maintenance checks on fuel lines should always be done.
Pressure regulators for fuel pumps have also contributed to the smooth pressure levels. These regulators are most of the time set up to a certain rating in PSI (for example: 40-50 PSI depending on the engine) to keep the fuel flow controlled through pressure relief valves. Should these valves fail, they can pass excess fuel overboard, causing a loss of pressure in the system. 15% of the fuel pressure incidents include a misaligned or damaged regulator, typically on higher mileage vehicles.
Lastly, a lack of voltage to the pump — often due to corrosion in the wiring or a weak battery — will reduce the pump output. Fuel pumps need a stable voltage to work, and that is rarely lower than 12-14 V. Anything below this range greatly decreases pressure & thus, fuel flow. Many of these pumps are built to the maximum and if they are not fed well regulated voltage, it may be a little higher if the volts are low. Check the electrical items for this sort of problem, especially in cars over 10 years old.
If you’re looking for quality and credible options to solve these problems, reliable sources like Fuel Pump have products specifically designed to maintain a stable pressure and resist wear from ethanol.