10 Signs of a Bad Fuel Pressure Regulator

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The fuel pressure regulator sounds like a simple and unimportant piece of equipment. This part is small but it’s important to your fuel system and engine running smoothly. 

Unfortunately, it’s hard to diagnose and determine when you are having issues with your fuel pressure regulator. 

Don’t worry. I’m here to help. In this post, I will go over the different signs of a bad fuel pressure regulator and what you can do to fix it. 

Symptoms of A Bad Fuel Regulator

1. Engine Misfires

One of the most common signs of a bad fuel pressure regulator is when your engine begins to misfire. This happens because your fuel pressure regulator is in charge of managing the fuel to air ratio inside your engine. When the fuel to air ratio inside your engine is off, this will cause misfires.

The misfires typically happen because there is not enough fuel and too much air inside your engine. The result is that your engine won’t fire the cylinder properly, and it will cause a misfire.

If you are not familiar with a misfire, a misfire sounds like a popping or backfiring sound. These sounds are sudden and occur quickly.

Below is a video of what you might hear when your engine misfires.

2. Poor Engine Performance

When you are driving with a bad fuel pressure regulator, your engine performance will begin to suffer. This includes reduced acceleration, fuel economy, and engine power.

The main reason that your engine performance will suffer is due to the fuel-air mixture inside the engine. A bad fuel pressure regulator will often result in an imbalanced mixture with fuel or air.

This is often referred to as running lean (high air-to-fuel mixture) or running rich (high fuel-to-air mixture).

When this happens, your engine is not running at the optimal fuel mixture combination. This can cause your engine to suffer.

Some of the most noticeable issues running lean or running rich can cause reduced fuel efficiency, loss in power, or weak acceleration.

If you experience any of these issues, then you should consider checking your fuel filter and using an ODB code reader to help you diagnose the issue.

The great thing is that ODB can give you codes that will tell you if your engine is running rich, lean, or if there is an issue with your fuel pressure regulator.

3. Leaking Gasoline

A dangerous symptom of a bad fuel pressure regulator is gas leaks. Unfortunately, the only liquid that a bad fuel pressure regulator is gasoline. 

Gasoline can start leaking from a fuel pressure regulator if there is any damage or wear and tear on the regulator. 

Some common reasons that cause a leak in a fuel pressure regulator include: 

  • Ruptured diaphragm 
  • Malfunctioning vacuum 
  • Ripped or worn down gaskets and seals

If you see gas leaking from your car or gas on any other components inside your hood, you should immediately inspect your fuel pressure regulator. 

You should also inspect your fuel pressure regulator if there is a strong scent of gasoline inside your hood. 

4. Black Smoke Coming from Exhaust

Another common sign of a bad fuel pressure regulator is black smoke coming from your exhaust. Again, the intensity can vary, but this is a major concern if there is dark smoke coming from your exhaust.

One of the main reasons a bad fuel pressure regulator can cause black smoke is that it can cause your engine to run rich.

When your engine is running rich, it’s burning too much gasoline. This results in heavy, black smoke coming from your exhaust.

You should inspect your car and use an ODB reader to identify if there are any issues with the fuel pressure regulator or if your engine is running rich.

5. Black Spark Plugs

When your spark plugs are black, this is referred to as carbon fouling.

Your spark plugs will typically turn black if you are driving with a rich fuel-to-air mixture. This can cause carbon fouling and can result in misfires and reduced fuel efficiency.

Carbon fouled spark plugs can cause your car to misfire and also reduce the effectiveness of your engine.

If you see black spark plugs, you should begin to inspect other parts of your car to determine the issue.

You can use an ODB reader to help you identify which spark plug is causing the issue, if you are running rich, or if there is an issue with your fuel pressure regulator.

Your ODB reader may detect a fouled spark plug in some cases, but it may not detect any issues with your fuel mixture or fuel pressure regulator. If you do experience any of these issues, you should try to determine the cause of the issue.

6. Car Won't Start

A bad fuel pressure regulator can cause your engine not to start. If your fuel pressure regulator stops working, your engine will either run too rich or too lean.

In this situation, this can cause issues when you are trying to start your car. When there is not enough fuel reaching your engine, your car won’t start. Likewise, in some cases, if the fuel is too rich, it can damage your spark plugs and prevent your engine from starting.

Unfortunately, there are many reasons that can cause your car not to crank or start. This can make it hard to diagnose why your car is not starting.

One way to help you determine if the issue is with your fuel pressure regulator is if you hear a crank but no combustion to start the engine.

Typically, you won’t hear a crank when you try to start your engine if there is an issue with your battery or alternator.

7. Gasoline Leaking From Exhaust

Another common sign that your fuel pressure regulator is failing or going bad is if fuel or liquid comes out of the exhaust pipe.

If your fuel pressure regulator is failing, you will experience gasoline/fuel leaking from your exhaust pipe.

This happens because a failing fuel pressure regulator can cause your fuel mixture to become rich. This means that their ratio of fuel to air is not optimal. With rich fuel, there is too much fuel in the mixture.

With too much fuel in your fuel mixture after your engine ignites the fuel, there will be extra fuel in your system.

This extra fuel will make its way down and out of your exhaust pipe. If there is fuel coming out of your exhaust pipe, you can expect to experience black smoke coming from your exhaust as well.

If you see the liquid coming out of your exhaust, you should take a small sample and determine what it is. If it’s gasoline, you should take your car to a professional to help you choose the cause of the gasoline.

While a faulty fuel pressure regulator can be the cause, other issues can cause this as well.

8. Check Engine Light Comes On

If you are experiencing issues with your fuel pressure regulator, your check engine light is likely to turn on. 

There are many reasons that your check engine light might turn on. The best way to determine the cause of your check engine light is to use an ODB reader. 

The ODB reader will tell you the reason for the check engine light. Multiple reasons can trigger the check engine light. Some of the most common readings you might experience are: 

  • Rich fuel mixture 
  • Lean fuel mixture 
  • Damaged Fuel Pressure Regulator 

9. Small of Gasoline Coming From Dipstick

Another common issue associated with a failing fuel pressure regulator is the smell of gasoline on your motor oil dipstick.

When the fuel pressure regulator begins to fail, this can cause gasoline to start leaking.

When this happens, the fuel can leak out of the car or into other parts of your vehicle. One of the most common areas that gasoline can leak into is into the motor oil compartment.

When this happens, you can sometimes see the gasoline inside the motor. However, a more effective way to determine if there is gasoline inside your motor oil is to inspect and smell the dipstick. If there is any scent of gasoline, then you have an issue.

Motor oil and gasoline have very distinct smells. Therefore, there should never be the scent of gasoline on your dipstick.

10. Backfires and Issues Decelerating

When your fuel pressure regulator begins to fail it can cause your engine to run rich. The result is that this can cause a build-up of gasoline. 

This build-up of gasoline can cause your car to backfire. A car backfires when there is a build-up of gasoline and then it ignites inside the exhaust. This will result in a loud pop coming out of the exhaust. 

With a failing fuel pressure regulator, this backfires typically happens when you are decelerating. As a result, when you begin to decelerate you will experience a jerk forward or backward. 

If you experience backfires you should have a professional inspect your car or you can inspect your fuel pressure regulator. 

How To Test Fuel Pressure Regulator?

The fuel pressure regulator is a small but important part of your vehicle. Fortunately, checking and replacing your fuel pressure regulator is much easier than it sounds. 

If you follow the steps below you can test your fuel pressure regulator to determine if it’s going bad and what you need to do to replace it. 

1. Test Your Fuel Pressure Regulator Using a Gauge

The easiest and most effective way to test your fuel pressure regulator is using a fuel pressure regulator gauge. However, it’s important to note that you can only use a gauge if your fuel pressure regulator has an accessible valve known as a Shrader valve. 

Some vehicles don’t have a Shrader valve which means you have to use a different method. 

Testing the fuel pressure regulator is quite simple and easy to use.

  1. Keep your car off. 
  2. Plug your pressure gauge into the Shrader valve.
  3. Make sure you know what your fuel pressure should be for your car. You can find this online or on your owner’s manual. 
  4. Start your engine and leave it idling. 
  5. Check the fuel pressure in your system and make sure it matches the ideal range. 
  6. Remove the vacuum line from your fuel pressure regulator. You should experience an increase in your fuel pressure. This can range anywhere from 5 to 15 PSI. If you don’t experience the rise, then there is an issue with your fuel pressure regulator. 
  7. Turn off your engine and check your fuel pressure. The pressure should remain for around 5 minutes before its starts decreasing. 
  8. If your fuel pressure does not meet your car’s requirements, this is a sign that there is an issue. If your fuel pressure decreases quickly after turning off your vehicle, your fuel pressure regulator is going bad. 

2. Test Your Fuel Pressure Without a Gauge

Unfortunately, some cars don’t have a Shrader valve, which means you can’t use a fuel pressure gauge. This means you will have to find a different way to test your fuel pressure.

In the past, this wasn’t easy. However, today you can use a Bluetooth ODB reader. Bluetooth ODB readers use an app to display any codes and metrics from your vehicle.

It’s important to note that not all ODB readers provide fuel pressure readings. It’s important to confirm you can get this reading.

When you use an ODB reader, it should give you the fuel pressure. You can test the fuel pressure both with the vacuum line and without the vacuum line.

3. Check for Leaks

It’s also important that you check for any leaks. Remember that the only thing that the fuel pressure regulator can leak is gasoline. 

If you see gasoline leaking from under your hood or gasoline marks inside your hood or on the fuel pressure regulator then there is a problem. 

If there is a leak in your fuel pressure regulator you should get this immediately fixed. This is a serious issue that can leak to dangerous driving conditions. 

What Is a Fuel Pressure Regulator?

The fuel pressure regulator regulates the fuel pressure inside your engine. It does this by controlling the amount of fuel, and air enters your engine. The fuel pressure regulator adjusts air and fuel to enter to maintain a certain level of fuel pressure inside your engine.

The fuel pressure regulator uses a bypass valve, also known as the ball seat. The ball seat allows the fuel regulator to control the flow it allows fuel to pass through. By adjusting the ball seat, the fuel pressure regulator either increases or decreases fuel and air flow. As a result, by adjusting the fuel flow, the fuel pressure regulator can control the pressure inside the fuel system.

The fuel system starts with the fuel pump. The fuel pump will pump fuel into the fuel system, and the fuel will flow to the fuel injectors. The fuel injectors will then release the fuel either directly into the cylinders or into the fuel bay.

When the fuel injectors open, the pressure inside the fuel system decreases. To normalize the fuel pressure inside the system, the fuel pressure regulator much increase the pressure. To do this, the fuel pressure regulator closes the ball seat to only allow a small flow of fuel through the valve.

In turn, this reduction in pressure through the valve increases the pressure inside the fuel system. When the fuel injectors close, the fuel pressure regulator will open the ball seat to allow more flow, maintaining the pressure inside the fuel system again.

How Much Does It Cost To Replace A Fuel Pressure Regulator?

If you replace the fuel pressure regulator by yourself you can expect to pay between $125 and $250. If you have a professional repair your fuel pressure regulator you can expect to pay between $200 and $350. 

Fortunately, replacing the fuel pressure regulator is relatively cheap and easy to complete. 

Typically professionals can complete the repair in less than 2 hours and in many cases less than 1 hour. 

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