Common Signs and Symptoms of Bad Fuel Pump Relay

Modern automotive engines are designed to use a precise amount of fuel at any given moment. The fuel pump relay is responsible for this. So if you are to get the most automotive experience from your car, you need to recognize the common signs and symptoms of bad fuel pump relay.

The fuel pump relay is responsible for powering the fuel pump so that the precise amount of fuel is delivered to the injectors and, ultimately, the combustion chamber. It is a device that contains electrical components fitted into a small aluminum or plastic cylinder box.

It comes in different ratings and dimensions and is situated in different locations in the vehicle (depending on the brand and model).

Going by the role of the fuel pump relay, we are going to discuss symptoms of a bad fuel pump relay and how to fix it.

Symptoms of Bad Fuel Pump Relay 

There are several reasons for which a vehicle’s fuel pump relay can go bad. None of these reasons are good, and they almost always lead to the same result; a problematic driving experience. It is essential to know the signs of a faulty fuel pump relay that you could test and replace it where necessary.

Here are a few fuel pump relay fuse is blown symptoms to look out for:

how to test a fuel pump relay

Engine Issues

One of the apparent signs of a bad fuel pump relay is issues with your engine. The reason is simple.

Turning your ignition is meant to provide the fuel that creates the combustion explosion. A bad fuel pump relay will not relay the required electrical power to the fuel pump, which in turn does not deliver the designated amount of fuel to the engine.

You might get the engine to crank when you turn the motor, but since there is no power to activate the fuel pump, there is no fuel being sent to the engine so that the vehicle won’t start, no matter how long you crank the engine.

In some cases, a bad fuel pump relay that is not providing enough pressure might even cause your engine to misfire. So if you have ever asked, “can a bad fuel pump relay cause misfire”, the answer is yes.

There are a ton of other reasons why your engine might have performance issues. Bad fuel filters can be one of such reasons. That said, an excellent place to start your checks would be the fuel pump relay.

A Silent Fuel Pump 

An electrically powered fuel pump often makes a whining sound when you start your vehicle. The whirring sound shows that electricity is being relayed to the fuel pump and fuel is being pumped to the engine. The reverse is the case with a faulty pump relay.

When electrical power is no longer being relayed to the fuel pump, it goes silent when the ignition is on. Although there are other reasons for a quiet fuel pump, it is often silent because its power source has been cut off and has become non-functional.

Loss of Power 

Without constant and specific amounts of fuel, your vehicle’s engine won’t function properly. You are likely to experience a loss of engine power when there is a reduction in fuel being relayed to the engine.

This loss of power might be because of a failed fuel pump relay or fuel pump failure both of which ultimately affects the fuel that gets to your vehicle’s engine. It could also be one of the symptoms of a bad fuel pump. Once the fuel is cut off, the engine loses power and stalls. So, whenever your vehicle stalls suddenly, then you might have a failed fuel pump relay.

Engine warning lights Come Up

Your fuel pump relay will not trigger a code, but it sets a sequence in motion that leads to a code coming on. When the fuel pump relay fails, no fuel gets sent to the car’s fuel system. This lack of fuel then causes specific sensors to come on when there is an absence of the required levels of air and fuel mixtures.

So sometimes, when you see the check engine lights on your dashboard, the root cause might be a failed fuel pump relay and not a bad fuel pump

A Burnt Fuel Pump Relay

This situation is arguably the most obvious sign that you have a failed fuel pump relay because a burnt relay is irreversibly damaged. A burnt fuel pump relay often is a result of high current or voltage. A burnt fuel pump relay might lead to serious fires happening in your vehicle in some scenarios.

FAQs:

Q: Will A Car Run With A Bad Fuel Pump Relay?

That depends on the extent of damage to the fuel pump relay. Once there is an issue with your fuel pump relay, the fuel supply to your vehicle’s engine gets cut off, and the engine loses power and stalls.

 If the fault in the fuel pump relay is minimal, the vehicle might be able to start after a while. On the flip side, your car will not start if the fuel pump relay is completely damaged. So can a fuel pump relay work intermittently? It depends on the extent of damage to the relay.

Q: “What Causes A Fuel Pump Relay To Go Bad?”

There are many reasons why your fuel pump relay can go bad, and they are all linked to the way it operates. The most common cause of a fuel pump relay going bad is electrical power surges that increase the voltage.   The fuel pump relay is designed to have a winding that causes contacts to pass current or voltage.

 In some cases, the current or voltage might be so high that the contacts get burned. In other instances, the signal coil gets shorted because the signal was at a high voltage or current.

Q: Can AutoZone Test A Fuel Pump Relay?

 AutoZone fuel pressure test gauges are great for troubleshooting your vehicle’s pump relay once it is a fuel-injected vehicle. You would need to have a Schrader valve test port for the AutoZone test gauge to work with. However, if your car does not have such a valve, then you could improvise using an adapter.

The AutoZone test gauges make the troubleshooting process convenient and straightforward.

Q: Can I Bypass the Fuel Pump Relay?

You could bypass a fuel pump relay by using a jumper assembly that comes with a toggle switch that you can use to turn the fuel pump on and off manually. Here is something you should know. It is okay to bypass your fuel pump relay if it is something of a test for the wiring or the relay. However, if your fuel pump works after you must have bypassed the fuel pump relay, the relay is most likely bad. It is a bad idea to try to drive around with a vehicle that has a jumped fuel pump relay.

That said, a fuel pump relay bypass offers a way on how to start a car with a bad fuel pump relay.

Q: How Do You Test A Fuel Pump Relay?

It is pretty simple to do that. Follow these steps

Park the car on safe and level ground

Engage the vehicle’s parking brake and put the transmission in “Neutral” or “Park.”

Turn the ignition key in the “ON” position.

After doing this, try to listen hard for the sound of the fuel pump, this is often a faint buzzing or clicking sound that might escape your notice if you don’t pay attention. Do not be bothered if you don’t hear any sounds. Proceed to the next step

Locate the fuel pump relay

For most cars, the fuel pump relay is situated in the engine compartment. The internet, the owner’s manual, or the service manual all of these are great go-to resources for locating the relay. You might even find a fuel pump relay diagram while searching for the location.

Once you have located the relay, try to pay closer attention to it to listen to the clicking or buzzing sound while the key is still in the “ON” position. You might get someone to join you at this point.

 Disconnect the negative cable from the car battery

The idea is to disable the power that is sent to the fuel pump and the related circuits. A wrench or socket set should make this task easier for you.

Remove the fuel pump relay

You can do this using a pair of needle-nose pliers if you find it difficult to do with your bare hands.

Set Your Multi-meter tool to resistance mode

At this point, you should connect test lights (preferably multi-meter) to the load and battery pins in the fuel pump relay. Connect the ground of the power supply to the ground pin in the relay.

Send power to the input voltage pin.

The multi-meter tool should make a beeping sound every time you do this. If that does not happen, your fuel pump relay is either broken or burned out.

Testing your fuel pump relay should be the next step after you have noticed any of the symptoms described above. Here is a video on how to test a fuel pump relay. It should make the troubleshooting process easier for you.

Final Words

It is essential to know and recognize the common signs and symptoms of a bad fuel pump relay, and how to fix it to prevent further damages that could result from it. Why? Because y our vehicle’s fuel pump relay is a vital component that prompts your fuel pump to start once you fire your engine. It is prone to wear and tear that could cause it to get damaged like all devices.

Once the fuel pump relay goes bad, the fuel supply to the engine is cut off, and your engine stalls. We have described some of them in this article, so hopefully, you can avoid the complications of a bad fuel pump relay like engine misfire.

Osuagwu Solomon

Osuagwu Solomon is a seasoned automotive technician for the past 9 years, and a technical writer. He loves writing about auto professional repair guides, DIY repair guides, and buyer’s guide. After spending six years in the automotive workshop, he decided to impact his knowledge to people aside his domain, and he has achieved this by centering his Automotive writing skills on REPAIRS.

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