Fuel Pump Relay – How a Fuel Pump Relay Works

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A Fuel Pump Relay pressurizes the fuel pump when it is time to build up fuel pressure in the rail. That is to say, the job of the fuel pump relay is to generate a voltage signal and supply current to the fuel pump.

Fuel Pump Relay

However, a faulty fuel pump relay is one of those things drivers should expect when they have a car issue. So, when a driver turns his key to start his car, it’s expected that everything turns over. But if it doesn’t the person will probably jump to the most common culprits, the battery, the starter, or the alternator.

What will be your next action if those parts are in order? That is why you need to read this write-up till the end. Because there are some other potential causes like a faulty fuel pump relay.

Fuel Pump Relay

You might be wondering what a fuel pump relay is, where’s it at, and how do you know if it’s working the way it should? Asking the above questions is very necessary and very important in other to find the correct fix to the problem. So, that’s why this write-up will be unleashing important information about the Fuel Pump Relay, how to fix the issue, where the relay is located and lots more.

What is a Fuel Pump Relay?

This is an electronic component that is embedded in virtually all vehicles that has an internal combustion engine. It is mostly located in the fuse box found in the engine bay. It also works as the primary electronic switch that controls power to the fuel pump.

However, it is usually controlled by the ignition or Powertrain Control Module, and when turned on, will provide current to the fuel pump so that it may function. So, as the fuel pump relay controls power to the fuel pump, if it eventually develops a fault, it can cause issues with the fuel pump. This brings about drivability problems for the vehicle.

How a Fuel Pump Relay Works

When you turn the key, your car’s ECM will send a signal to the fuel pump to put the right amount of fuel into the combustion chamber to start your engine.

The car’s ECM does this by controlling a relay, which is the fuel pump relay. So, when the relay gets enough power, it switches over and sends that power to the fuel pump. But when it doesn’t, it switches off and the fuel pump shuts down.

However, the original position for the fuel pump is off, otherwise, you’d constantly run out of fuel! The fuel pump relay is the gateway between the ECM and the fuel pump.

Where Is the Fuel Pump Relay Located

The exact position of this can vary depending on what you drive. However, there are two major locations you should check. They are;

  • Below the hood of your vehicle by the firewall or
  • Below the dash on the passenger side of your vehicle

Moreover, no matter where your fuel pump relay is, just know that you’re looking for the fuse box.  You’ll need to take the fuse box cover off to find the fuel pump relay.

Signs of a Faulty Fuel Pump Relay

Before you proceed to start swapping relays and ordering new parts, please if you notice any of these signs.

Unable to Start Your Vehicle

Car refusing to start is the most likely sign of a faulty fuel pump relay, though, mostly overlooked. Most drivers mostly assume it’s either a dead battery or a bad starter, but if the combustion chamber doesn’t have any fuel, there is no way the engine will start.

However, when you turn on the key, you should hear a click in the fuse box. But if you don’t hear it and you can’t start your vehicle, you might have a faulty fuel pump relay.

Check The Engine Light

If your car is starting but it is having mechanical problems, then a check engine light, it might be your first sign that you have a faulty fuel pump relay. Lots of engine codes will point you straight to the fuel pump or fuel pump relay.

Engine Stalling

If your car is stalling out after starting it, it could be a whole lot of problems, but one possible cause is a faulty fuel pump relay. And because of how easy it is to check, it’s always worth ruling it out early in the troubleshooting process.

Poor Acceleration

If your car’s fuel pump relay is on the fritz, then you might start to notice some acceleration problems when the fuel pump relay doesn’t kick on and off as it should. This poor acceleration can quickly turn to engine stalls, and eventually, you might not be able to start your vehicle at all!

Take note of this; sometimes it doesn’t break down slowly. It might work today, and the next day you might not be able to get your vehicle started.

I Can’t Hear A Noise or Kick From the Fuel Pump

When you’re starting your vehicle, you should hear your fuel pump kick on as it tries to send fuel to the engine. Though you might not be able to hear it from the cab of your car, if you send someone back to the fuel pump, they should hear it kick on.

But if they can’t hear it kick on, you either have an electrical malfunction, a faulty fuel pump, or a faulty fuel pump relay.

What Causes a Fuel Pump Relay to Fail?

Technically a short or other electrical malfunction can cause the failure of the fuel pump. Though, the most common cause of a broken or damaged fuel pump relay is age. So anytime the relay clicks over it wears down just a little bit, and after about 100,000 –  200,000 miles, that’s quite a few clicks.

It’s eventually just too much for it to handle and it either won’t click over again, or it won’t click back to its original position. However, it is normal, and as long as it isn’t happening over and over again, there’s nothing you need to do other than replace the relay.

How to Test a Fuel Pump Relay

There are three easy methods you can test the relay. The first two methods aren’t completely foolproof but can give you the result.

  1. Swap the Relays

There is more than one relay in the fuse box, with different functions, but exactly the same. So, all you need to do to check any individual relay is swap it with another relay! If the problem goes away, then the relay is what’s causing the problem.

Though, the only disadvantage of this method is that if you have two faulty relays nothing will change. That’s why it’s best to make sure you’re swapping in a brand new relay.

  1. Use a 9 Volt

Check a relay with a 9-volt battery, remove the relay and connect the positive and negative terminal of the 9-volt to the two studs on the relay and listen for a click.

The 9-volt battery terminals line up, so you won’t need jumper wires or anything, making it a quick and easy test. If the relay is working, correctly then it should click over when you connect the battery and click back when you take it off.

The disadvantage with this method is that your relay doesn’t typically operate off of 9-volts. Though is close enough to troubleshoot almost any relay, if you have one right on the edge, then you might get a false reading.

  1. Check Resistance Levels

Using a multimeter is the only 100% best way to check a relay. Relays work through resistance. So, once they get enough power, it overcomes the resistance and clicks the relay over. Though the exact number of Ohms your relay should have can vary some, it should be between 50 and 120.

Few Ohms means your relay is always activated, while too many means it won’t open at all. If the relay shows an open or out limit reading, it means the coil is bad and you’ll need to replace it.

Fuel Pump Relay Replacement Cost

If after testing and you found out the problem is from there, there’s really no need to get a mechanic. Replacing the relay is quick and easy, which means all you need to do is purchase the part.

When you buy the new relay, all you need to do is pull out the old relay and push the new one in. Is it very simple right?

In terms of making purchases, an average fuel pump relay only costs about $25. The prices vary based on location, model, types etc. Also, if you take it to the mechanic you will be charged for if(Extra expenses).

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