A faulty fuel pump can, in fact, cause the engine to backfire due to improper fuel flow. The fuel pumps work to create a continuous supply of fuel at appropriate pressure to the engine, usually between 40-60 psi on most vehicles. A faulty or inefficient fuel pump could mean inconsistent fuel delivery and a potential overly lean or rich air-fuel mixture. The lean mixture, especially, may cause misfires that may result in the engine backfiring. Industry reports say that as many as 15% of all engine misfires and backfires in older vehicles can be traced to the fuel system, including a faulty fuel pump.
For example, in 2017, a study by the Automotive Service Association (ASA) found that one of the leading causes of backfiring in high-mileage vehicles was poor fuel delivery, especially those with fuel pumps that have been in use for over 100,000 miles. This is because a worn-out fuel pump can’t maintain the correct pressure or volume of fuel, leading to combustion issues. When fuel is lacking, ignition is delayed, and the excess fuel ignites in the exhaust system, producing the characteristic popping or backfiring sound.
When the fuel pump cannot deliver enough pressure or if it is failing intermittently, then the engine might have fluctuating power that leads to inconsistent combustion. As put by Bosch, the fact that fuel pressure fluctuation as low as 5 psi can cause modern engine management systems to misfire merely is based on the exactingly controlled fuel delivery for smooth performance of the engine. A frequent backfiring usually characterizes the case where fuel detonates at the wrong time, either in the intake manifold or the exhaust system, and may easily create major engine damage without their solution.
Moreover, a faulty fuel pump can also cause damage to other components. For example, if the engine runs too lean due to insufficient fuel supply, it can cause overheating of the engine’s components, such as the valves, piston rings, and even the fuel injectors. Reports from the American Automobile Association, or more commonly referred to as AAA, indicate that almost 20% of all engine backfire cases result from inadequate fuel delivery, usually due to a malfunctioning or worn-out fuel pump.
When diagnosing this problem, one should monitor both the fuel pressure and the capacity of the fuel pump to deliver fuel at the correct flow rate. This mostly happens because, for a majority of the cars, when the fuel pump fails to meet the requirements of the specifications of approximately 40-55 GPH, it will not burn correctly and might lead to backfiring. In cases involving extreme measures, like forced induction with vehicles, a faulty fuel pump issue may be considered quite critical as the engine will require higher flow under load.
In short, a malfunctioning fuel pump can seriously affect the performance of the engine, and if left unattended, could lead to serious problems like engine backfiring, which may necessitate costly repairs. Anyone planning to install a replacement or an upgraded fuel pump should first check the specifications for proper flow rate and pressure as a way of avoiding these problems. For more information on fuel pumps, check out Fuel Pump.