bad Fuel Pump Relay

The fuel pump relay is an electrical component that’s activated when the ignition is turned on – its main purpose is to provide and maintain a consistent voltage supply to the fuel pump. Its located inside the engine bay in the fuse box and it’s controlled by the ignition or PCM. Since the fuel pump relay provides power to the fuel pump, if you have a bad fuel pump relay that’s failing, then it can cause a lot of problems with your vehicle. Luckily, rather than going to the dealership to get your vehicle inspected, there are a few symptoms you’ll notice in your vehicle that’ll signify your fuel pump relay is bad.

As soon as you turn on your vehicles ignition, the fuel pump relay is turned on – it then puts pressure on the fuel pump then the oil pressure in the fuel system takes over to help the system start your vehicle. The relay is basically a switch that uses a small voltage to provide a signal to open or close the contact of a higher voltage.

Symptoms of Bad Fuel Pump

Overtime, components in your vehicle start to wear out and this is normal for all components including the fuel pump relay. It could be failing due to dust, or a sudden voltage increase – this can affect the fuel pump relays performance over time and this won’t be good for your engine since it’s a vital component. If the fuel pump relay can’t transfer the correct voltage, you’ll notice that there’s a few signs.

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Engine Doesn’t Start

The fuel pump relay is meant to maintain the voltage to the fuel supply so it’s ready to start going once you turn on your car’s engine. If the relay fails or doesn’t work as it should, then the engine won’t start. If there’s no fuel supply to the engine system due to a failing fuel pump relay, then your engine won’t start. The engine runs on fuel and without the combustion of fuel and air in the chambers, the engine won’t be able to start. This can also happen if you have a clogged fuel filter so you shouldn’t use this as a direct symptom.

Engine suddenly turns off

If there are any signs of weakness within the fuel pump relay, then the engine is going to suffer with it. Therefore, if the fuel pump relay is faulty, then this will directly show within the engine. You may start stalling or in a bad scenario, the engine could misfire. If the fuel pump relay isn’t allowing enough fuel to the combustion chamber, the engine will turn off. The engine needs to run on the right air-fuel mixture – sometimes can run on a mixture that’s too rich but if the mixture of fuel is inadequate, the engine could turn off.

Unresponsive Fuel Pump

If your fuel pump isn’t responding when the car starts, this could be a sign that the fuel pump relay isn’t functioning properly. When you start your car, the fuel pump will start working immediately and you might hear a slight buzzing sound that will signal this. If the fuel pump relay isn’t delivering the right amount of oxygen to the fuel pump, then it won’t be able to start when the car starts. If you have a faulty fuel pump relay, the fuel pump won’t respond – if you’re unaware its because you have a bad fuel pump relay, then it could cause you to keep turning on the ignition in the hope that you hear the fuel pump start working.

Loss of Power

If your vehicle loses power whilst you’re driving, this could indicate that the fuel pump isn’t too good. Your vehicle may stop completely, or it could lose power whilst on the road partially. This could be because the combustion chamber isn’t receiving the right amount of fuel, therefore the correct mixture can’t be created. If you notice that your vehicle loses power and you notice some other symptoms with it, then this can indicate that the fuel pump relay isn’t working correctly.

Engine starts for a few seconds

You may start your car and the engine comes on as normal and you hear all the right noises, then you may notice that the engine power goes down or turns off and you aren’t able to drive your vehicle. If the fuel pump relay was functioning incorrectly as soon as the engine turned on, it’ll be directly affected, therefore, you’ll notice that the engine loses its power. If you notice this whenever you start your vehicle, it could indicate that the fuel pump is bad and needs replacing.

No Noise from Fuel Pump

Along with an unresponsive fuel pump, if you turn on your vehicle and you don’t notice that there’s a noise come from the fuel pump, this could be because of the bad fuel pump relay. Most fuel pumps produce a humming vibrating noise that can be heard from the outside of your vehicle near the fuel tank. If the fuel pump relay isn’t working correctly, the power will be cut off to the fuel pump which will stop it from working and you’ll hear silence when the ignition is on.

Check Engine Light Comes on

If you notice that the check engine light comes on in the background, this could indicate the fuel pump isn’t working correctly. The vehicles computer constantly monitors the emission control system, and this includes the fuel pump and the fuel pump relay. If the PCM notices that the fuel pump relay isn’t providing the correct voltage reading, the ECU could trigger the check engine light.

Since the check engine light can come on for a host of reasons, it can be difficult to pin down the problem to a bad fuel pump relay. Luckily when the check engine light comes on, it provides the vehicles computer with error codes that’ll let it know what the exact problem is. To check what these error codes are and what they mean, you’ll need a professional OBD2 scanner. You can use an OBD2 scanner (View on Amazon) to diagnose the error codes the vehicles computer is giving you. If you see that the error code is related to the fuel pump relay, then you’ll need to get them checked out in your local workshop. A professional OBD2 scanner will allow you to look up the error codes on the scanner, whilst a standard OBD2 scanner tool will force you to look up the error codes meaning in your car’s manual. You should receive an error code of P0230 or P0231.

High Mileage

As you may know from the Second Law of Thermodynamics, everything wears down over time so at some point in the vehicle’s history, the fuel pump relay will need replacing. If you notice that you’ve done between 100-200k miles, then it’s time to start heading to the workshop because your fuel pump relay could be at the end of its lifetime.

Long Engine Start Time

Usually when you start your vehicle, you hear the engine start shaking and you’ll feel the vibrations in your vehicle. If you start your car and you notice yourself cranking the motor for more than 10 seconds, this could be an indication that you have fuel problems – any problems with fuel could be down to a bad fuel pump relay.

How to Fix Bad Fuel Pump Relay

If the fuel pump relay is bad, then its a sign that you’ve been failing to maintain your vehicle. Maintaining things like your battery and other parts of the vehicle will allow the fuel pump relay to function properly over a long period of time. If not, over time the fuel pump relay will go bad and you’ll have to get it repaired at a dealership which can cost a lot.

If you want to avoid relay problems or other issues and save $100s of dollars that you’ll spend at the auto repair shop, you’ll need to service your vehicle often – you can use our mechanic-rated Auto Maintenance and Repair Manual to do this. It’s basically what mechanics use to go through your vehicle to check if there are any problems that need fixing. As soon as they notice the most minor problem, they’ll ask you to fork out some money even though it’s a problem you can fix yourself in minutes – the manual will teach you how to maintain your vehicle every few thousand miles and it’ll teach you how to fix minor problems that mechanics will ask you to pay for; saving you money in the long run.

A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.

How to Test Fuel Pump Relay

If you want to know for sure that there’s a problem with your fuel pump relay, you can test it out using a multi-meter (View on Amazon).

1. Make sure that you park your vehicle on a level ground and make sure to put the engine on parking brake and put the transmission in Park or Neutral. If you have a garage, it’s best to leave your car here rather than in the open.

2. Turn on the ignition and make sure all the devices are on. As you turn on the ignition, you should hear the fuel pump active as soon as the key is turned. If you’re in an enclosed environment, then it’ll be easier to hear the fuel pump make noise than if you were out in the open. If you can’t hear the fuel pump don’t worry – it’s quite hard to hear so make sure your environment is as quiet as possible.

3. Since the relay is located in the engine compartment inside the fuse box, you’ll need to raise the hood to gain access to the fuel pump relay. To locate the fuel pump relay, you can check your service or owner’s manual. If you can’t do this, then you can check below on how to find your fuel pump relay.

4. You need to make sure that you can hear the fuel pump relay in the engine compartment after lifting up the hood and turning the ignition on. If you were unable to hear the buzzing noise from the relay, you can get a friend to listen out for it to.

5. You need to disconnect the negative battery cable from the car battery – this will disable the function of the fuel pump and all the components related to it.

6. You’ll need to remove the fuel pump relay – to do this, you need to know it’s located and if you aren’t able to remove it by hand, then you need to use needle nose plyers to pull them out.

7. Grab a multi-meter (View on Amazon) and set It to resistance mode. Resistance mode will allow you to test the fuel pump relays resistance to measure if it’s working. You should see 4 pins on the fuel pump relay. The ground, input voltage, battery, and load which will be connected directly to the fuel pump relay – you need to connect the multi-meters probes to the load and battery pins on the relay. You need to provide a power supply of 12-volts to the fuel pump relay and connect the ground of the power supply to the ground pin.

8. Feed the power into the input voltage pin – each time the power touches the input voltage, the multi-meter should beep and provide a resistance. If there’s no resistance, your fuel pump relay is broken, and you need to get it replaced.

9. If you are going to get the fuel pump relay replaced, you need to make sure that it’s the same fuel pump relay that’s fitted into the fuel box.

Where’s the Fuel Pump Relay Located

The fuel pump relay is located inside a fuse box in the engine compartment. The fuse box looks like a long black box and it contains the fuel pump relay as well as other fuses and relays. It’s unlikely that the fuel pump relay is located differently in your vehicle but it’s still possible. Because it’s a switch that’s controlled by the PCM, chances are it’s in the fuse box. If you can’t find it here, then you’ll need to check out your vehicles service manual or the repair manual – if you no longer have this with you, you can consult with a mechanic.

Fuel Pump Relay Replacement Cost

If you’re going to get the fuel pump relay replaced after noticing that you have a faulty one, you should be aware that the average cost of replacement is between $100 – $250. The fuel pump relay itself is going to cost between $20 and $50 while the labor cost will take up the rest of the price. If you’re going to have the vehicle inspected for a bad fuel pump relay, then it could cost more. If you want to save money, you should purchase the fuel pump relay (View on Amazon) separately – this can be acquired on Amazon or in the nearest car shop.