How Do You Know If Your Fuel Pump Relay Is Bad?

A malfunctioning fuel pump relay causes anything from having trouble starting your car to the engine not turning over at all. An fuel pump relay is about the size of a pea, but a critical part in controlling the electrical current to the Fuel Pump. In a healthy relay, the Fuel Pump is supposed to receive 12 volts upon turning the ignition switch to the ON position and that relay should last the lifespan of the car which can be 100,000 to 150,000 miles. However, like all parts, relays can fail over time, so identifying potential malfunction early saves money and additional damage to the fuel system.

The prime example of a bad fuel pump relay is a car that refuses to start but cranks. This when the relay fails to supply power to the Fuel Pump, where delivery of a fuel stops. In fact, AAA Automotive Reports states that when there is a no-start condition, a customer complains that the vehicle is not running, the faulty fuel pump relays represent about 15-20% of such conditions. If you suspect this problem, check that the fuel gauge is working—if it is and the fuel gauge reads fuel but the car doesn’t start, then the relay is not supplying the Fuel Pump.

One more symptom of a faulty relay is power cutting on and off to the Fuel Pump. The car will start when first cranking over, but then later may die or not restart. According to a study performed by Bosch Fuel systems, approximately 30% of sporadic engine stall events could be attributed to faulty relays that would fail to supply voltage (intermittently). This kind of trouble is near impossible to test directly without the use of diagnostic equipment but can be diagnosed quickly by turning the key to the “on” position and listening for the Fuel Pump priming. The absence of the familiar hum of the pump could indicate a bad relay.

“The smallest part can sometimes be the most painful piece,” Robert Martin, an automotive technician, says. If you want to quickly test the relay, you can try swapping it with another relay of the same type found in the vehicle (the horn relay or headlight relay are good options). If the car works with the swapped bank relay, the original bank fuel pump relay is definitely defective. But if this test fails, the problem may go deeper, like a sagging Fuel Pump or even a wiring problem.

Another option to diagnose a bad fuel pump relay is to check for the voltage. With a multimeter, test for voltage at the terminal of the fuel pump. If you can’t get more than about 12 volts when you’re listening to the ignition, your relay isn’t sending the right amount of current. If those voltages jump around or are erratic, it may signal a problem with the relay’s internal contacts.

Finally, it is not unusual to see mechanical failure in the relay. In older cars or cars subject to harsh driving conditions the internal contacts in the relay can burn out or corrode. As Automotive Repair News explains: ‘In vehicles of over 10 years old, around 10% of relays will suffer a mechanical failure with a total loss of function.

As it turns out, if the relay is the problem, replacing it is a cheap fix, usually costing somewhere between $30 and $100, depending on the make and model of the vehicle. But you can notice the relay going bad; you will need to listen to the pumping of gasoline (the fuel pump) process, although driving with a bad relay can put extra stress (possibly lead to) on the Fuel Pump.

If you are looking for an alternative relay or Fuel Pump, then Kemso Fuel Pump provides reliable, high-quality products that are built to last and perform consistently well. For more information, click here: Fuel Pump

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