A: Why is my fuel pump running all the time? Most often this occurs due to a bad fuel pump relay. Controlling the electric current, the relay turns on and off at which that initiates or denergize the pump. If the relay sticks in the "on" position, the fuel pump stays on even when the engine is turned off. This can lead the pump to fail prematurely due to overheating. In any case, the relay should turn off the pump a few seconds after the engine is turned off in order to keep system pressure (usually between 40 and 60 PSI) up for the next start.
A failed fuel pressure regulator is one of the other potential causes. The regulator stabilizes fuel delivery to the engine. When it does go bad, your fuel pump will run all the time as it is trying to keep the pressure in spec. As an illustration, when the fuel pressure is below a critical threshold–often around 50 PSI in most contemporary automobiles–the pump could remain on for an excessive period of time to help correct for the fall.
Running all the time could be as simple as wiring leading to a fuel pump. If wiring to the pump is damaged or shorted it can send an always on signal to run the pump constantly. In one of the Hyundai recall in 2019, due to defective wiring to the fuel system some of its models experienced fuel pump malfunctioned and had issues such as running continuously leading battery drain and overheat. This illustrates how the quality of wiring can affect the operation of your pump.
High temperature is also one of the reasons why the pump continue to operate when it should not, because as in this case electrical components that control the operation may become faulty. When the fuel pump is oversized to cope with the long-term survival of a pump in very hot climates, electrical components housed internally may be stressed due to high temperatures. Fuel pumps that fail in very hot climates up to 15 per cent more often than those in cooler weather are a general example of heat related problems.
That is to say, in the words of popular mechanic Scotty Kilmer, “When something that shouldn't run runs, you have an electrical problem or a mechanical failure. This tidbit reinforces the need to fix things such as a fuel pump that is constantly running now instead of later, and subjecting your engine or electronic components to additional damage.
Letting the fuel pump run dry, for instance, will cut down on a temporary component in use and allow it some time to cool off. Being able to check the relay and the wiring as well as knowing how to test for a bad pressure regulator can stop this lack of performance. If you suspect an issue, it is better to change the parts which are malfunctioning earlier rather than doing an expensive repair.
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