Yes, an old worn-out fuel pump will lead to similar idle issues as when it can no longer provide a steady stream of fuel to the engine. Fuel pumps are vital in a modern vehicle for keeping the pump pressure at its designed levels which usually ranges between 40 to 60 psi and provides smooth engine operation. This pressure can vary if the pump is faulty, which may cause rough idling or even stalling of the engine. Based on industry data, fuel pump failures account for roughly 15% of all idle-related issues in 100k mile+ vehicles. This number goes up as the fuel pump ages from normal wear and tear, a common occurrence in high-mileage vehicles.
The fuel pump is designed to deliver a consistent flow of fuel for the engine whether it was idling or at WOT. When running at an idle the engine is taking in less fuel, so any stumble or cut-off would be more noticeable. The fuel injection system with sensors are programmed to idle and keep the right air-fuel mixture, but if that levels of the fuel pressure is not suitable or drop below from standard than it motive out erratic idling or even stalling in engine. That may sound absurd, but in multiple cases we've heard a failing fuel pump will have an engine idling smoother again within minutes of being replaced, just illustrating how vital the fuel system that feeds your engine is when it comes to performance.
Fuel systems have been in the top 3 causes of vehicle recalls over the past years. For example, Subaru recalled around 200,000 cars in 2020 because the fuel pumps were faulty and led to rough idling and engine stalling. It was a recall that finally hammered home the idea of regular fuel delivery, particularly during low engine speeds. Both the Bosch and Delphi people suggest regular service to avoid idle stability problems, especially in areas that have extremely hot ambient temperatures because in these environments fuel pumps are given a very hard time.
But fuel efficiency also drops when the pump does not maintain optimal pressure for the fuel. The engine can sometimes compensate for fuel delivery problems by consuming more fuel, and drivers may see a decrease in miles per gallon (MPG) as a result. A failing fuel pump will lower fuel efficiency by an average of 5-10%, especially during idle or low-speed driving. The decrease in efficiency also results in increased emissions, so regular fuel system checks are equally important for performance and environmental reasons.
Fuel system integrity is an oft-mentioned topic among engineers and those that live and breathe in the world of automotive equipment. Like Kiichiro Toyoda, the founder of Toyota, once said: failure is the mother of invention — and constant failure (in this case writing cars off) for mechanical problems such as fuel pump failures leads to advancements in vehicle design. With this, a continuous assessment with tools like the fuel pressure gauges can detect premature indications of fuel pump failure so you are able to avoid major repair work later.
To learn all there is to know about the affects of fuel pumps on idle stability and overall fuel system performance, please visit Fuel Pump.