The main tests for the voltage supply of the fuel pump are to ensure adequate delivery and to diagnose problems such as stalled or poorly accelerating engines. Poor performance by the fuel pump is usually related to any kind of insufficient or disrupted voltage feeding. The fuel pump, usually powered by approximately 12 volts, will not work or result in poor performance if it suffers a voltage drop.
Locate the electrical connector of the fuel pump. This can typically be found near the fuel tank or on the fuel line itself, depending on the vehicle model. Disconnect the power connector to access the wires supplying the fuel pump with power. The fuel pump relay and fuse are often located near the fuse box and can be tested separately to eliminate external sources of electrical failure. For example, one of the most common problems-a blown fuse-will not allow power to reach the fuel pump.
Checking the Voltage Using a Multimeter To check the voltage with a multimeter, place the meter on DC voltage and insert the probes into the fuel pump connector terminals. A system in good working order should show a voltage of about 12 volts when the ignition is turned on. If it is much lower-voltage, say below 10 volts, then the car definitely has a wiring issue or failing fuel pump relay. As a matter of fact, according to most motor experts, over 15% of fuel pump failure can be attributed to reasons like voltage drops due to damaged wiring or faulty relays.
Another, more sophisticated way to check the voltage is to check it under load-that is, while the fuel pump is operating. In this way, it is assured that the system is capable of sustaining the required voltage during the operation of the pump. If the voltage sags severely under load, it may indicate a problem with either the fuel pump or the electrical feed.
In these cases, the problem has often been traced to either a faulty fuel pump control module or an ignition switch that could have failed over time. Sometimes, problems with voltage supply can be fixed by replacing or repairing one of these components. In such cases, replacement of the component will often get the voltage right and clear the problems in the fuel pump. This easy-to-repair but important issue is the cause of more than 10% of fuel pump-related complaints in car diagnostics.
Proper testing and diagnosis can save time and money in the case of fuel pump failure, as many times, rectifying the voltage problem will restore functionality to the system. For more reliable and efficient fuel pump systems, it’s always best to consult a reputable source like Fuel Pump.