Diagnosing a low voltage Fuel Pump requires a step-by-step process to find what is preventing it from operating correctly. Usually, a good Fuel Pump works within a voltage of about 12 volts, which is the standard voltage most vehicle batteries provide. Anything below that voltage can easily cause poor fuel delivery, rough idling, or even stalling. If the voltage to the Fuel Pump is always less than 12 volts, then the pump will not work properly, and the engine will suffer as a result.
To start troubleshooting a low voltage problem, a multimeter should first be connected to the power connector of the Fuel Pump. This is typically done with the ignition “on”, but the engine not running. A reading lower than 12 volts reflects issues with power supply to the Fuel Pump, including wiring fault and a bad relay. It is also probable that corroded or loose connections-very much common in vehicles with a history of running under harsh environment conditions and high age-account for the voltage drop. According to the National Renewable Energy Laboratory, a study showed that poor electrical connections can cause a voltage drop of up to 20% and may greatly reduce performance.
Next is to check the Fuel Pump relay and fuse; these are responsible for feeding power to the Fuel Pump. A faulty relay may cause a voltage drop because it will not supply the required current to the pump. In fact, it is estimated by the Automotive Maintenance and Repair Association that nearly 30% of Fuel Pump failures can be directly related to a problem with either a relay or fuse. Generally, this is a quick fix when it comes to low voltage problems, as replacing the relay or fuse can restore the proper voltage to the fuel pump.
Additional checks should also be made on the vehicle’s battery voltage. A weak or undercharged battery can also cause a low voltage supply to the Fuel Pump. If the battery voltage is below the standard 12-14 volts, it can affect the overall electrical system, including the Fuel Pump. According to automotive experts, a failing battery is responsible for approximately 15% of Fuel Pump malfunctions. If the battery turns out to be the problem, it may have to be replaced before further diagnosis of the Fuel Pump.
Lastly, the wiring to the Fuel Pump should be checked for any damage or wear and tear. Over time, exposure to heat, moisture, and friction can degrade wires and cause power loss. With much exposure, especially in older models, the wiring harness can get brittle, crack, and lead to intermittent connections causing voltage low. In such instances, if the problem areas are identified, then there could be a need to replace wiring or connectors in order to ensure proper voltage supply to the Fuel Pump.
It also means the voltage at the power connector of the fuel pump must be tested, the condition of the relay and fuse reviewed, the battery voltage inspected, and whether the wiring is intact checked. By identifying these on time, potential further problems related to performance may be saved, plus it may avoid high costs due to repairs.