This is when there is an issue with the fuel pressure regulator, which controls and regulates a balance in the system. Fuel system requirement: Different engines have different specific fuel pressure needs but for the most part, it is pretty much what all vehicles require between 30 to 60 PSI. When the regulator malfunctions fuel pressures can go beyond this range, in some cases spiking as high as 80 PSI. This is quite the strain on your fuel pump and can cause problems with engine performance like a rough idle or losing power when you are accelerating.
Over- pressurization often results from clogged fuel return lines. In standard fuel systems, the unused fuel that did not flow through the engine is simply returned back to its tank via a return line. When the line clogs with either trash or rust, it hampers fuel return and pressure builds up. This is usually common in cars with older fuel systems where internal parts have broken down over time. According to industry reports, approximately 20% of return line blockage are the root cause behind fuel system failures in aged vehicles.
Another problem you can have is an over-pressurization due to a malfunctioning fuel pump relay. When there is a problem with the relay and how it controls fuel pump power, this can sometimes cause the fuel pump to run at full capacity all of time even when not needed. This raises the fuel pressure above normal operating ranges. Relay issues are often a hot topic in automotive forums when it comes to fuel pumps, and some users even claim that their vehicles started seeing up to a 15-20% drop in gas mileage due to excessive pressure from constantly cycling the pump.
Over- pressurization can occur when the aftermarket fuel pump is installed with excessive calibration. A common trick is to use an aftermarket pump that subtly pumps more fuel in -- especially if it's designed for high-performing engines. Without a proper fuel pressure regulator, these pumps can make pressures higher than the engine is calling for and create an over-fueling situation that results in poor performance. A case in point is an episode in 2019 where the warranty claims started pouring in after a flurry of fuel pump installs continued to occur on modified sports cars that began having engine misfires or delivering lousy gas mileage.
When you ask the question "why do I have a high pressure fuel pump?" usually of a pressure regulator failure, return lines are blocked or relays have failed and some aftermarket components do not match the system. Resolving all of these effectively can save your engine from long term damage. Get information about fuel pumps and their parts at Fuel Pump.