Relays are used on fuel pumps to manage the high current required to constantly pump fuel without overloading the electrical system of the vehicle. Most fuel pumps operate on a 12-volt circuit and at constant amperage-usually within the region of 10 to 15 amps. Wiring the pump directly to the ignition switch would require high current through the switch itself, possibly leading to overheating and wear on the switch in the long term. Instead, it acts as a relay-intermediate device that offers a high-current path to the fuel pump, drawing only very minimal control currents from the ignition system. Essentially, this will prevent overloading on the ignition components and increase their lifetimes.
Relays also guarantee reliable fuel pressure, which is critical to engine performance. Fuel pumps need to pump fuel under constant pressure. A relay provides the constant power supply to maintain such fuel pressure and avoids voltage drops that would create disturbances in fuel pressure. Poor connection may starve the fuel pump of adequate voltage and develop erratic fuel delivery, possibly leading to lean air-fuel mixtures, engine hesitation, or stalling. According to specialists in automotive technology, voltage stability, as maintained by the relay, is critical to ensure proper engine performance and fuel efficiency.
Another advantage of the relay usage is safety, enabling fast fuel pump shutdown in case of emergency. In case of an accident, a relay connected to the car's safety system can cut power to the fuel pump to minimize the danger of fuel leakage and fire. If there wasn't that kind of relay-controlled cut-off, a constantly working fuel pump would increase the danger in case of collision.
Relays are designed to meet higher fuel flow demands by fuel pumps for high-performance applications. Most of the modified engines require more than 300 liters per hour of fuel delivery, which puts immense electrical demand on the vehicle. A relay can efficiently handle such an electric need of fuel pumps and provide the Fuel Pump with much greater capacity without causing electrical failure or overheating.
