Early detection of fuel pump relay failure is basically founded on attention to specific signs that the electrical system is malfunctioning. It includes but is not limited to symptoms like intermittent engine stalling. The fuel pump relay supplies power to the fuel pump, and if it starts to go bad, the fuel pump may not get consistent voltage. A typical relay should always provide 12 volts to the fuel pump. A simple drop in voltage of just 10% can easily cause the engine to misfire, developing stalling at any instance, especially when it is at an idle or running at low speeds.
Another symptom is poor starting of the car. Once the fuel pump relay goes bad, the fuel pump may never promptly turn on, leading to poor and/or delayed engine starts. In a normal occurrence, a good fuel pump would prime the system in under two seconds once the ignition key is turned. If it takes more time or the engine cranks several times before it actually starts, voltage may not always be passing properly through the relay. Because of malfunctioning fuel pump relays causing wide-scale starting issues, a major automotive manufacturer issued a recall in 2018 for several of its models.
Other symptoms of a relay problem could be clicking sounds from the fuse box. Due to the fact that the fuel pump relays are simply electromagnetic switches, a weak relay could make an audible clicking sound as it tries to pull in. With prolonged wear and tear, some relays lose their efficiency by 10-20% and randomly trip on and off, which may cause the fuel pump to also turn on and off.
Less fuel economy is another symptom. In case the relay in the fuel pump happens to fail intermittently, then the potential of the fuel pump to sustain a continuous pressure will be reduced. Fuel pressure should be constant at about 40 to 60 psi depending on the vehicle. A faulty relay may lower that pressure about 5 to 10 psi, and thereby the engine is forced to run less efficiently than usual; this can lower fuel economy by up to 15%.
Firstly, voltage can easily be checked using a multimeter to confirm indeed the relay has failed. Measurement of voltage at the output terminals of the relay while the engine is running will indicate whether or not correct power is supplied through the relay. Any reading below 12 volts with large fluctuations implies the failure of the relay and thus needs replacement. These relays usually range in cost from $20 to $50 and are thus a cheap component to replace compared to the possible damage of a fuel pump in fail. For more information on diagnosis and preventing Fuel Pump issues visit Fuel Pump.