The fuel pump relay allows your vehicle to start up and shut down by activating the fuel pump. In addition, it ensures the fuel pump has a reliable and consistent source of electricity. Since it’s a crucial electronic component of the fuel delivery system, you will surely notice when the fuel pump relay is not working properly.
The main reason why a fuel pump relay fails is due to excessive amperage. The fuel pump could be drawing too much current, which can blow out the fuel pump relay. The fuel pump relay also degrades over time and usage.
This article will discuss the work of a fuel pump relay, what makes it go bad and common symptoms of a bad fuel pump relay.
What is a fuel pump relay?
The fuel pump relay is a fuse located in the car’s fuse box that is essential to the combustion engine’s performance. It supplies a steady flow of electrical current to the fuel pump.
When you turn the ignition, the fuel pump relay responds by generating a voltage signal and sending power to the pump. The pump then pressurizes the fuel system and delivers the correct amount of fuel to the injectors. The injectors then spray this fuel into the combustion chamber.
When the engine starts running, the fuel pump relay shuts off, and the oil pressure sending unit supplies the fuel pump with electricity instead. When you switch off the ignition, the fuel pump relay activates again to power down and turn off the fuel pump.
What causes a fuel pump relay to go bad?
Several factors could ruin your fuel pump relay. They include:
Age
Every time the fuel pump relay clicks over, and it degrades a little bit. So if your car has high mileage or you have driven it over 150,000 miles, it becomes more likely not to click back into its original position. Some common fuel pump relay damages that occur over time include coil wear and contact point rust.
Electrical power surges
Another reason for the relay failure is the voltage may be too high that the contacts on the relay burn. The contacts are essential in passing the current through. In other cases, high voltage can cause the signal coil to get shorted. A weak car battery can also cause electrical surges.
Wiring issues
Wiring issues such as loose connections, a short in the line, bad connection, or damage on the wire can disrupt the constant and proper flow of power from the battery to the fuel pump relay.
Signs and symptoms of a bad fuel pump relay
If the fuel pump relay goes bad, you will notice it immediately. Also, bad fuel pump symptoms can vary depending on your vehicle’s make and model and the problem’s severity. Below is a list of all the signs and symptoms that indicate you have a bad fuel pump relay.
The engine stalls or stops suddenly while driving
A faulty fuel pump relay cuts off power to the fuel pump and causes your engine to stall while driving. This is due to inadequate fuel or pressure. The relay could also be too damaged that the car suddenly shuts down while driving since no fuel is reaching the engine.
If your vehicle stops when you can’t call a mechanic, you can perform a fuel pump relay bypass to activate the fuel pump using jump cables.
Rough acceleration or idle
A bad fuel pump relay will not be able to maintain a sufficient supply of fuel. So you’ll likely hear rough sounds from your engine when accelerating or when your car is idle.
The engine doesn’t start.
Sometimes the fuel pump relay doesn’t break down slowly. It might work one day, and you won’t start your car the next. If the fuel pump relay is completely dead, your fuel pump won’t have any power to deliver fuel to the engine. So you may be able to crank the engine, but there will be no fuel to start the combustion process.
Check engine light
Like other electrical components, the fuel pump relay connects to the vehicle’s ECU(Electrical Control Unit). So when the relay starts failing, it prevents sufficient fuel from reaching the car’s fuel system. This reduced fuel will set off the fuel pressure sensor and trigger some trouble codes, which you can read using an OBD2 scan tool. The OBD scan tool will display the following codes; P0230 and P0231.
Poor engine performance
Besides the check engine light, a bad fuel pump relay will start affecting the performance of your engine. A stalling engine could have many reasons, and one of them is a bad fuel pump relay—the relay powers the fuel pump, which provides fuel for combustion.
But a faulty relay will not send the required voltage to activate the fuel pump; in turn, your engine won’t have enough fuel to start to run properly.
In other instances, the bad relay won’t create enough pressure, thus causing your engine to misfire.
No noise from the fuel pump
A functional fuel pump usually produces a low-volume hum or kick when it sends fuel to the engine. You will typically hear this sound from the rear of the vehicle, near the fuel tank, as the pump pressurizes the fuel delivery system. Also, when you turn the ignition on or off, you should hear the fuel pump relay clicking in the fuse box.
But when the fuel pump relay fails, the pump will not have the power to operate; thus, it will run silently. So you will not hear any noise from the fuel pump when starting the car or accelerating.
Fluctuating fuel consumption
A bad fuel pump relay can cause either increased or decreased fuel consumption. This means your engine will run lean sometimes and rich at others.
Most of these symptoms could also be from a faulty fuel pump. So testing the fuel pump relay using a multimeter should confirm it’s defective and needs replacing.
Can a fuel pump relay work intermittently?
Yes, a failing fuel pump relay can work intermittently. Since the fuel pump relay directs current to the fuel pump, any problem with the relay will affect the fuel supply into the combustion chamber. Eventually, this will affect other parts of the car. Some of the factors that can make a fuel pump relay work intermittently:
- Bad ground – Incorrect grounding of the relay can cause it to work intermittently. It will also lead to issues with the contacts
- Worn contacts – The fuel pump relay wear down over time which can cause problems with turning on and off the pump.
- Loose terminals – If the connection between the terminals and the coils on the relay is loose, it can cause the fuel pump to not work at times.
- Coils – The coil gets weak over time and affects the occasional performance of the fuel pump.
Can a bad fuel pump relay cause a misfire?
Yes, a faulty fuel pump relay can cause the engine to misfire and other problems with the ignition system, especially at idle. A defective fuel pump relay won’t provide the necessary power to activate the fuel pump. Insufficient fuel reaching the combustion chamber causes incomplete or no combustion. Therefore, your vehicle won’t start, no matter how much you crank the engine.
Can a bad fuel pump relay cause low fuel pressure?
A defective fuel pump relay can cause low fuel pressure. Therefore your engine will crank but won’t start at all. The fuel pressure in your vehicle ensures the fuel injectors spray a fine air-fuel injection pattern for the engine to function properly. This pressure also depends on the car manufacturer.
So if the fuel pump relay is faulty, it cuts the power to the fuel pump, causing it to deliver fuel at little to no pressure. This will cause poor engine performance, such as a hard start, stalling, hesitation, or misfiring.
Conclusion
Although the fuel pump relay is durable, it is not immune to damage or deterioration over time. This will prevent your fuel pump from running properly and, in turn, affects your engine’s performance. If you experience one or more of the symptoms listed above, you should have a professional mechanic diagnose and replace the fuel pump relay immediately to avoid worse issues.