Typical indications of a worn fuel pump are anything from abnormal performance and delayed starting to bad gas mileage, engine misfires and strange noises or a fluctuating pressure meter. The pump is no longer able to hold enough pressure, typically 40–70 PSI on a fuel-injected engine, making restart more difficult. If the pump is worn, it may take a number of seconds to build this pressure, leading to extended crank times. For fuel pumps with this kind of delay on high-mileage vehicles, the problem usually amounts to internal component wear — degraded impellers or weakened motor windings.
Poor mileage often signals a fuel pump that no longer provides a steady stream of gas. With a worn pump it is unable to supply the exact fuel-to-air ratio required by the engine for the best combustion process and this will reduce miles per gallon by 10 – 15% or more. In older cars, the pump can also gradually lose efficiency which is why mechanics recommend keeping an eye on MPG changes as early warning signs of an impending failure.
Inconsistent pressure can result in inconsistent fuel being injected into the system, which will present itself as an engine misfire, a common symptom of a worn fuel pump as well as poor acceleration. Worn out pumps may deliver fuel inconsistently leading to transient fuel starvation and therefore misfires. In fact, fuel delivery-related misfires make up as much as 20 percent of all engine performance complaints, according to a Society of Automotive Engineers study.
Abnormal sounds, especially squeaky whining or grinding, indicate that the fuel pump is stressed and therefore strained, typically because a clogged filter or low fuel level is forcing the fuel pump to work overtime. Extended stress makes parts wear faster as parts wear out quicker when the pump is pushed past its limits. When less wear occurs, and this can be mitigated by replacing fuel filters every 30,000 miles (inert and free-flowing filters will allow the pump to run less).
As automotive expert Ed China says, “Unusual sounds are usually the first signs of problems.” Recognizing these early indicators could prevent complete pump failure and preserve your vehicle’s performance.
To prevent these symptoms of wear, a quality Fuel Pump protects against wear and tear by ensuring a consistent delivery of fuel and ensures the efficiency of the system and longevity of the overall fuel system.