A weak or failing fuel pump can cause a wide range of symptoms, each pointing to different issues within the fuel system. One of the most noticeable signs is difficulty starting the engine. A weak fuel pump may not provide the required fuel pressure, resulting in extended cranking before the engine finally starts. These fuel pumps generally operate within a pressure range of 30 to 60 psi, depending on the vehicle, and if that pressure falls below the recommended range, it may lead to hard or no start conditions. According to AAA, poor fuel delivery can degrade the performance of an engine as much as 15%, and one of the first symptoms of a weak fuel pump is hesitation while accelerating or even a severe drop in power.
Other very common signs of a failing fuel pump include the stalling of the engine, particularly when the vehicle has been in use for some time. The weak fuel pump cannot provide consistent fuel pressure, so the engine stutters upon load or when idling. It might happen due to gradual loss of fuel pressure or because of some intermittent failure in its electrical components. According to Bosch, fuel system stalling is one of the most common complaints among motorists experiencing failing pumps, and if left unattended, it can be carried all the way to complete breakdown.
Some strange noises from the fuel tank may also indicate a failure in the fuel pump. A whining noise, generally high pitched, that comes from the rear of the car is one of the common symptoms of a failing fuel pump. This can be because the bearings inside the pump wear out, the pump becomes clogged with debris, or the fuel filter clogs and forces the pump to work harder. The fuel pump has to work hard, and as it begins to wear out, that motor can make more noise because the friction increases inside. General Motors reports most fuel pump failures are just a result of debris or dirt or rust clogging the inside mechanism of your pump and making strange noises.
A loss in fuel efficiency or increased fuel consumption can be related to a weak fuel pump too. If the fuel pump is not pumping at the correct rate, the engine will run richer than normal, which may result in poor fuel economy. According to the U.S. Department of Energy, a faulty fuel system can reduce fuel economy by up to 10 to 15%, and often the key to restoring normal performance is replacing a failing fuel pump.
In some instances, a failing fuel pump may trigger the check engine light. Modern vehicles possess fuel pressure sensors that monitor the operation of the fuel pump. If the pressure is either too low or fluctuates erratically, the computer system of the vehicle can develop an error code and turn on the check engine light. Diagnostic codes such as P0087, which indicates low fuel pressure, are common with fuel pump issues. Toyota recommends using a scan tool to read these codes and help pinpoint the exact cause of the problem.
Poor acceleration, especially under heavy throttle, can also be directly related to a weak fuel pump. When the engine is not getting enough fuel during acceleration, it will hesitate or refuse to respond to the driver’s command. This can be highly evident in case of accelerating uphill or speeding. According to Bosch, about 20% of poor driveability problems, including poor acceleration, were found to be related to low fuel pressure or faulty fuel pumps.
Lastly, a sudden loss of power or rough idling may mean the fuel pump has gone bad. The pump will either not be able to keep the required flow rate, whereupon the engine runs unevenly and even misfires. This occurs most in older cars with greater mileage, where wear and tear on the fuel pump components can cause wild fluctuations in performance.
To make accurate diagnosis and replacement, the fuel pump must be tested under correct conditions. Always use an excellent replacement part from a trusted fuel pump supplier such as Fuel Pump.