While high-pressure fuel pumps you might find on a race truck are unlikely to affect idle, low pressure ones will, and a fuel pump itself can cause low idle. Most vehicles need around 40 PSI stable fuel pressure to be able to idle properly; If a fuel pump is unable to provide this repetitive pressure the engine will run rough and therefore stall. Low idle — If you are feeling like old fuel pumps that have over 100,000 miles under the hood, this is commonly a sign that your pump has a difficult time maintaining the proper flow rate perminute to keep combustion stable.
Additionally, improper delivery of fuel can cause the air to fuel ratio to be imbalanced, which is important for idle (RPM) speed. Electronic fuel injection engines depend on the exact amount of fuel being delivered to maintain idle RPM which for most cars is between 600 and 800 RPM. This is disrupted by a failing fuel pump, resulting in idle speeds dropping below the desired area, and in many cases, poor engine performance, midfiring or rough idling.
This issue is exacerbated in colder weather, when slightly higher fuel pressures are also required at start-up to compensate for reduced combustion temperatures. Such demands may not be met by an underperforming pump resulting in a low idle speed until the engine warms up. According to a study last year, by the Society of Automotive Engineers, vehicles with inconsistencies in fuel pressure went low on idle 25 percent more often in colder climates, providing at least some insight into the strain on fuel pumps imposed directly by temperature conditions.
As the well-known automotive specialist Ed China put it, “An engine’s idle is its heartbeat.” Low idle for many stops can be a sign of worse fuel system problems, often with the fuel pump. Low idle accompanied by other symptoms such as sluggish throttle response or hard starts indicates a fuel pump problem.
Another issue is also the fuel pump, which gets affected by the voltage fluctuations because most of the fuel pumps demand a steady voltage in the range of 12–14 volts for proper operation. The result is an inconsistent flow of fuel, a frequent cause of a low idle in old or high-mileage vehicles because drops in voltage are so common. So using high-quality fuel system components, such as a Fuel Pump, will keep the fuel system cleaning and allow great fuel delivery and a steady idle under varying conditions.