While fuel pumps do technically be able to run on low voltage, low voltage really can make big differences in their effectiveness, causing problems such as: inconsistent fuel delivery, reduced pressure, and even long-term damage. By design, a regular fuel pump is supposed to operate at approximately 12 volts because it allows the pumps to deliver a specific range of pressures, typically from 30 to 80 psi, depending on the requirements of the vehicle. Below this voltage, sometimes in the area of 10 volts or less, the pump might have a hard time keeping up adequate fuel pressure; symptoms here include rough idling, hesitation, or complete engine stalling in extreme cases.
Low voltage affects the fuel pump’s ability to provide a constant flow rate, normally rated in LPH. For example, while a pump may be rated at 130 LPH at 12 volts, only about 90-100 LPH may be delivered at lower voltages. This can easily cause a lean fuel mixture under high-demand situations, such as when one rapidly accelerates or drives uphill. In high-performance vehicles with a more precisely tuned fuel system, low voltage typically equates to fuel starvation, increased opportunity for misfires, and even some engine knock because of the lack of sufficient fuel. Low voltage to the fuel pump typically arises due to a couple of things, which are generally poor wiring connections and failing relays among others. Over time, it has been found in some high-mileage vehicles that some wiring deteriorates and develops resistance, which drops the voltage delivered to the pump. Sometimes this is more obvious when operating in cold-weather conditions, due to the fact that the output of the battery itself is sometimes lowered and can be considered to be a low-voltage problem. This is where most mechanics would tend to check wiring and batteries if there were issues regarding fuel problems in the delivery system, since the threshold of 100,000 miles had been reached or exceeded.
Some high-performance applications use voltage regulators for the express purpose of supplying the fuel pump with constant voltage. In such systems, it will exhibit some smoothing to current draw in order to provide consistent pump performance during fluctuations in battery voltage. In the majority of regular vehicles, though, a well-maintained electrical system should keep the voltage within a range that’s acceptable to handle fuel pump operations.
As Henry Ford, the great automotive innovator once said, “Quality means doing it right when no one is looking.” Testing the voltage that the fuel pump receives is one assurance it gets the proper voltage to maintain efficiency and avert sudden failures. See Fuel Pump for a high-quality fuel pump that handles various demands in style.