There are a few common symptoms that hint towards a failing fuel pump relay. The fuel pump relay sends power to the fuel pump so that the engine can receive fuel. A failure in the relay would mean the fuel pump will not get the electrical signal it needs, which could result in a drop off in performance from the engine.
One common symptom of a bad fuel pump relay is difficulty starting the engine. Before the engine can start, the fuel pump has to pressurize the fuel system and a bad relay could stop this from happening. You may also encounter sporadic starting issues or a complete lack of fuel pump noise after you turn the key. One in seven no-start complaints filed with automakers can be attributed to a faulty fuel pump relay, which was well observed when the National Institute for Automotive Service Excellence (ASE) conducted a 2020 study that said it accounted for ~7% of all no-starts.
Engine Stalling Is Also Symptom of Bad Relay The relay switches the power to fuel pump, and when it fail sometimes while the engine is running, then fuel pump will stop working, interrupting with feeding gas. This may lead to stalling, especially when the engine is under load or idling. It starts stalling randomly then after a few minutes it can start. It may be the cause of a defective relay(Q&A)
A bad fuel pump relay can also cause the check engine light to come on. The engine control module (ECM) is able to monitor the fuel pressure, so if it begins to speculate that the fuel pump may be starting to act indiscriminately in any way, shape or form no matter how intermittent and carries out an operation fault, then DTCs like P0230 (Fuel Pump Primary Circuit Malfunction) or P0087 (Fuel Rail/System Pressure Too Low ) are flagged. The OBD-II scanner would be able to read these codes and give you an idea of what the problem is.
Finally, if you have a multimeter, you can test the fuel pump relay. You can measure between the terminals of the relay to see if you have continuity (or voltage on a hot side) to know if it is working or not. Continuity may not exist or may not be continuous as usual, and there are proper readings of voltage according to the electrical schematic of your vehicle. A faulty relay, however, is a simple and inexpensive fix generally ranging from $20-$50 depending on the vehicle.
Automotive expert and businessman Elon Musk said that “an electric drivetrain consists of the smallest parts that can influence the performance of the car” when speaking about electrical components. For instance, a fuel pump relay can fail and create headaches.
Summary: Symptoms such as trouble starting, engine die-offs, or check engine lights should be indications of a failing fuel pump relay. For more information, visit Fuel Pump and check out Diagnosing or Replacing Your Fuel Pump.