The process of diagnosing fuel pump relay issues begins with symptoms such as an engine stalling, no-start conditions, or an intermittent fuel pump operation. This is often symptomatic of the relay not sending a steady signal of 12 volts to the fuel pump, which normally runs at a constant 12 volts. In such cases, If the relay fails Pump will not be receiving power and hence fuel cannot be delivered properly and leads to low-pressure or complete shutdown of the pump.
To test it, find the relay, usually found in the fuse box, often under the hood. Test the terminals of the relay for continuity with a multimeter. With the relay energized, the continuity should exist across certain terminals in the majority of relays. If there is no continuity, the relay could be bad, and in that case, replacing it can make it operate normal. Voltage drop is when a multimeter reading is less than 12 volts, decreasing fuel pump efficiency by 10-15%, leading to intermittent fuel flow, and stalling of the engine.
Another relatively simple test is to listen for clicks when the ignition is turned to the “on” position. You should hear the relay click as it engages and sends power to the fuel pump. If there is no click sound it can either because of a bad relay or corroded connections. The most usual reason why relays tend to burn out is because, corrosion in the terminals, increases the resistance, which makes the relay heat up and burn out sooner than later. Use of electrical cleaner at terminals sometimes can be helpful in case of mild corrosion which allows the relays to perform properly and also have the Fuel Pump to function.
You can also confirm relay problems by swapping the suspected relay with an identical relay in the fuse box. If it Does, your old one is probably Bad. Fortunately, relays only cost $10-$20 bucks each, so replacing them is a cheap way to resolve potentially larger, and more expensive fuel pump or wiring problems.
Identifying and correcting relay issues provides a steady power supply to the fuel pump, which helps maintain consistent fuel pressure and reliable engine performance. Relay checks on a routine basis play the most significant role, especially with older vehicles, in ensuring we do not face sudden failures in the Fuel Pump, thereby adding to the overall reliability of the vehicle.