Auto Parts Guide, Car Maintenance

Symptoms of a Bad Fuel Pump and Fuel Pressure Regulator

fuel pressure regulator

If your vehicle is not driving smoothly or does not start smoothly all the time, the problem may be that the fuel pressure regulator is malfunctioning, because it may affect the fuel supply to the engine combustion chamber.

However, although fuel pressure regulator problems are common, it is easy to miss them if you don’t know what to look for. In some cases, you may even mistake the fuel pressure regulator for other reasons.

What is a Fuel Pressure Regulator?

The fuel pressure regulator works exactly as its name implies-it regulates the pressure of the fuel when it flows to the injectors. Where the regulator is located, its exact role depends on the type of fuel system used in the vehicle.

Continuous oil return system

Older vehicles have a continuous oil return system. With this design, fuel is delivered from the fuel tank to the fuel rail through the fuel pump. The fuel supplied by the fuel pump exceeds the demand of the engine. In order to maintain proper fuel pressure under all driving conditions, a fuel pressure regulator is used. The regulator maintains proper fuel pressure by sending excess fuel back to the fuel tank through the return pipe.

In continuous fuel systems, the fuel pressure regulator is usually installed in the fuel rail. The fuel pressure regulator is controlled by engine vacuum.

fuel pressure regulatorNo oil return system

Most modern vehicles use a non-return fuel system. As the name suggests, this type of system has no return pipe to the fuel tank and no externally mounted regulator. It controls the fuel pressure in the fuel tank. The fuel pressure regulator is usually built into the fuel pump assembly. This design can achieve more precise fuel control and reduce emissions.

Some non-return fuel systems adjust the fuel pressure by changing the duty cycle of the fuel pump (on time). The fuel pump is usually controlled by a powertrain control module (PCM) or a dedicated fuel pump control module (FPCM). The fuel pressure sensor is used to monitor system operation.

Why is the Fuel Pressure Regulator Important?

Although many fuel pressure regulators use vacuum-operated mechanical diaphragms to change fuel pressure, modern diaphragms are electronic and work in very different ways.

fuel pressure regulator


In both cases, the correct maintenance of the fuel pressure regulator is essential because it is directly responsible for distributing fuel to the engine. And a bad fuel pressure regulator will affect the performance of the engine.

How to Troubleshoot Fuel Pressure Regulator Issues

Before condemning the fuel pressure regulator, it should be tested. This is usually done by checking the fuel pressure downstream of the regulator with a mechanical pressure gauge. On many new cars, scanning tools can also be used to check fuel pressure.

fuel pressure regulator

On older vehicles with continuous fuel systems, the regulator can be checked by removing the vacuum hose. After removing the hose, the fuel pressure should increase by 8 to 10 PSI. Check for fuel in the regulator vacuum hose. This may indicate a diaphragm leak, which is also a good idea.

If the fuel pressure regulator is found to be damaged, it should be replaced. On most non-return fuel systems, this usually means that the fuel pump assembly must be replaced.

What are the Symptoms of a Bad Fuel Regulator?

 Decreased fuel efficiency

The main function of the fuel pressure regulator is to control the fuel pressure delivered to the engine. If the pressure is very low, the fuel will move in a very slow manner. The cylinder will not receive the right amount of fuel mixed with air. There is more air in the mixture than fuel. The engine will redouble its efforts to compensate. It will try to absorb more fuel. This causes the car to consume more gasoline than usual.

The same effect is possible when the fuel pressure is too high. This may cause the combustion chamber to “flood”. The engine has more fuel than air in the mixture. This also leads to a reduction in fuel efficiency.

There are other factors that can cause the fuel economy to decline. For example, a leak in the fuel delivery system can also be the cause of poor fuel economy. In any case, a decrease in fuel efficiency always indicates the poor performance of the fuel pressure regulator. This will help the mechanic diagnose the problem and find the cause of the problem for you.


Black smoke from the tailpipe

A normally running engine will never emit smoke from the exhaust pipe. This is one of the most powerful signals that the engine is using the correct air-fuel mixture. In some cases, the smoke will be somewhat white or gray. This is still normal. There are other factors that can help ensure the “correct” characteristics of the smoke from the exhaust pipe. However, if you notice black smoke coming out of the exhaust pipe of your car, one of the possible explanations is that there is a problem with the fuel pressure regulator.

There may be many reasons for the black smoke from the exhaust pipe. It may be due to a problem with the way the carburetor is installed. Black smoke in the exhaust gas may also be a sign of clogged air filters. In the worst case, a damaged injector will also produce black smoke.

People should never underestimate the possibility of fuel pressure regulator failure. As mentioned above, problems in this assembly can cause problems with the air-fuel mixture. The engine can burn more fuel than usual. The more fuel burned, the richer the gas passing through the exhaust system.


Oil spill

One of the symptoms of a problematic fuel pressure regulator that you may see in a car is a fuel leak. There are seals on both sides of the device. Damage to these seals may cause openings for fuel to pass through. The problem with seals is that they cannot last the life of the vehicle. Long-term use will also wear them out. With the rupture of the seal, fuel leaks easily.

A problem with the fuel pressure regulator is not the only cause of possible leaks in the fuel delivery system. It may be due to corrosion, the presence of contaminants, and problems in the fuel filter. Sometimes, incorrect electrical connections can also cause fuel leakage.

Fuel leakage always leads to a decrease in fuel economy. The engine is not getting the correct amount of fuel to produce energy. In this way, the engine will compensate. It will work harder to draw more fuel into its combustion chamber. If a fuel leak is found, it is best to locate it. If you are not sure how to perform the diagnosis, a mechanic can help you.


Poor acceleration

The poor performance of the fuel pressure regulator can also cause poor acceleration. This is one of the first symptoms that many car owners notice in their cars. When they step on the gas pedal, the car will not accelerate in a more normal way. This is very slow. No matter how difficult it is for you to step on the accelerator, the car will not travel fast enough.

A problem with the fuel pressure regulator is not the only cause of slow acceleration. This may also be a sign of a problem with the injector. Dirt and debris can accumulate on the tip of the fuel injector. This will block the tiny holes that spray fuel into the combustion chamber. However, such problems are easy to solve. You can use injector cleaner to help remove debris that may have accumulated on the tip.

Whether it is a problem with the fuel pressure regulator or the injector, slow acceleration is not a good sign. It always means that the engine is not receiving the correct air and fuel mixture in the combustion chamber.


Engine misfire

There are many reasons for an engine fire. The symptoms are also very obvious. You may notice very severe idling, violent acceleration, slow acceleration, and engine vibration. There are many reasons for an engine fire. This may be the cause of a problem with the spark plug or ignition coil. Injector problems can also cause the engine to misfire. This is also one of the symptoms of fuel pressure regulator failure.

A problem with this equipment may cause low fuel pressure. There is not enough fuel to reach the combustion chamber. You will hear strange noises from the engine. If left unused, you may also feel the vibration under the hood. If you continue to ignore this sign, you may damage the engine.

A mechanic can help you determine the exact cause of an engine fire. If it is a fuel pressure regulator failure, then the technician can recommend replacing it. If the cause is due to other reasons, he can also suggest other fixes. 

fuel pressure regulator


The engine cannot start

Engines that cannot be started may be caused by many problems. It may be because the battery is dead. You do not have enough power to start the electrical system of the engine, including the starter. Before considering the fuel pressure regulator failure, it is best to check the battery.

The engine may also fail to start due to a problem with the alternator. There are other potential reasons for the engine not starting. One of them is the failure of the fuel pressure regulator. We have already said that this device pushes fuel into the combustion chamber. If this function cannot be performed, your engine will not start.

In most cases, the owner must try to start the engine up to 5 times. There should be enough fuel in the combustion chamber by then. This will help start the engine. However, if you do notice this symptom, it is best to make a more accurate diagnosis. It should help to have a mechanic diagnose it for you.



The spark plug appears black

The engine needs the correct combination of air and fuel to produce power. This power comes from a controlled explosion in the combustion chamber. Therefore, the air-fuel mixture should be able to ignite at the right time. This is where the spark plug enters. It provides the necessary heating elements to ignite the fuel-air mixture.

Diesel engines do not need spark plugs. This is caused by spontaneous combustion. The air and fuel mixture is compressed under very high pressure. This caused the mixture to catch fire. Therefore, if your vehicle is equipped with a diesel engine, this phenomenon will not occur from a fuel pressure regulator failure.

The rich fuel-air mixture may cause black deposits to accumulate on the tip of the spark plug. When the mixture is ignited, it will produce carbon deposits and adhere to the surface of the spark plug. However, the problem with the fuel pressure regulator is not the only cause. It may also be that the fuel injector is leaking or the carburetor float is heavier than normal.


Problems in deceleration

You might think that the deceleration problem is not one of the signs that the fuel pressure regulator is malfunctioning. it is. Like problems during acceleration, a faulty fuel pressure regulator can cause problems during deceleration.

This problem is related to the excessive accumulation of gasoline. Because there is more fuel than the engine can withstand, it may be counterproductive. The continuous combustion of the engine enables the car to continue driving at the same speed. When you lift your foot off the pedal, it may take a while before you notice the car slowing down.

This may bring serious security risks. If you are driving at a high speed, an accident is likely to occur. It is difficult to adjust the speed when it needs to slow down. It is for this reason that one should never ignore this sign. Have a mechanic check your fuel system immediately to take the correct measures.


The fuel pump is loud

All devices in the car make sounds. Some are quieter than others. Most car owners may not even know the sound of a running fuel pump. In order to diagnose the problem in the fuel pump, it is wise to listen to the low buzzing sound when turning on the key of the ignition switch. This will activate the pump and pressurize it. You can also hear how the pump works during acceleration. There are audio files on the Internet to help you understand the sound of a fuel pump in normal operation.

The loud noise in the fuel pump may indicate several things. One of them is the failure of the fuel pressure regulator. Problems in the regulator may affect the function of the pump. If the equipment does not allow normal fuel to pass through the fuel rail, it may cause problems with the fuel pump. You will hear a harsh whine, especially during acceleration.

If you are not sure what caused the annoying noise, please ask a mechanic to diagnose it for you. A more thorough inspection of the entire fuel system can zero possible perpetrators.


Fuel in the car vacuum hose

One of the symptoms of fuel pressure regulators, a phenomenon that people can never ignore is the presence of fuel in the vacuum hose of the vehicle. This is an automobile part connected to one side of the fuel pressure regulator. If there is a problem with the regulator, fuel may leak into the vacuum hose. The only way you can diagnose this problem is to disconnect the vacuum hose from its connection to the regulator. Only then can you check whether there is gasoline or fuel in the vacuum hose.

Owners who cannot disconnect anything from the car will have to find a mechanic to do it for them. This also gives them an opportunity to identify other problems that may cause some or all of the symptoms we list here.

Also, check for signs of fuel on the outside of the vacuum hose. This usually happens immediately after turning on the engine.


10 Signs of a Bad Fuel Pump

Although the mechanical pump and the electric pump can be completely different, the problems of the two pumps have almost the same symptoms. Therefore, if you find any of the signs we will list below, you must replace the pump immediately no matter which pumps you use.


When driving at high speed, the engine may splash

When driving continuously at high speed, the first sign of fuel pump failure will appear. If you notice that the engine starts to splash at high speed, it means that there is an obvious problem with the fuel pump. Since the fuel pump cannot maintain a constant fuel supply flow rate at the required constant pressure, engine sputtering occurs.


The vehicle temperature rises significantly and then shuts down

Another important indicator of fuel pump problems is temperature rise. If the thermometer shows that the temperature of the vehicle continues to rise and then turns off, the fuel pump must be diagnosed and repaired immediately.

It is important to note that the increase in vehicle temperature can be caused by multiple issues that are usually very important. Therefore, even if you are not sure whether it is your fuel pump, you must send the vehicle to the nearest repair shop and repair it immediately.


Problem with fuel pressure gauge

The pressure gauge indicates the amount of fuel supplied to the engine. Every car has a certain amount of fuel, which must be continuously supplied to the engine so that it can operate normally.

If this amount of fuel is not provided to the engine, there may be a problem that may cause a serious failure.

The best starting point is the user manual of the vehicle. In this manual, it will tell you how much fuel should be supplied to the engine at any time. So what you can do is ask others to revive the vehicle while checking the pressure gauge. If the fuel pressure gauge shows less fuel than the required fuel quantity, the fuel pump must be repaired immediately.


The vehicle may lose power under pressure

If you return from a grocery store or use a vehicle to pull heavy objects while moving, the vehicle may be under pressure. Under high pressure, the weak part of the fuel pump will withstand additional pressure, making it difficult to provide the engine with the required fuel.


Sudden power surge when driving at normal speed

A component failure of the fuel pump may cause the vehicle to surge suddenly without any previous warning signal. When the fuel pump motor tries to resist the engine’s continuous demand for fuel supply, a sudden surge occurs.

fuel pump

A sudden decrease in gasoline mileage

There is a safety valve in the fuel pump to control the amount of fuel injected into the engine. If the pressure relief valve cannot be opened at the correct time, the fuel supply to the engine will exceed the required amount. As a result, you will start to notice that the car’s fuel tank needs to be refilled more times due to insufficient mileage.


Your vehicle may not start

In situations where the fuel pump is difficult, you may reach the point where you cannot start the engine. When the fuel pump is not working, no fuel will be supplied to the engine, so the engine will not start. Although the engine may start and spin, it will never start.

When diagnosing a fuel pump, the first thing you should do is to look for low pressure in the fuel pipe or a blown fuse.


Heard a strange whine from the fuel tank

According to experience, hearing the weird sound from a vehicle is a very bad signal, and you must act immediately. This is because these weird noises may be related to major problems that may cause complete engine failure or vehicle damage.

Just like the weird sound from any part of the vehicle, if you hear a harsh sound from the fuel tank, it indicates that there is a problem with the fuel pump.

During normal operation, your fuel tank pump will buzz. However, if the sound starts to grow louder and more like a whining sound, it indicates that the fuel is contaminated, the fuel pump is damaged, or the fuel tank is insufficient.


Difficulty starting the vehicle

Although we mentioned earlier that the fuel pump may cause the vehicle to fail to start, the failure of the fuel pump may make the vehicle difficult to start, but ultimately it fails to start.

As we mentioned earlier, the fuel pump continuously supplies the required fuel to the engine after turning on the ignition switch. The insufficient fuel pump may cause the vehicle to bend the crank several times to start. In difficult situations, you may need to turn the key several times before starting the vehicle.


Engine overheated

When the fuel pump is unable to provide the required amount of fuel to the engine, the engine will build up pressure, causing overheating. Engine overheating is one of the most serious engine problems and can cause rapid engine failure.


How Much Does it Cost to Replace the Fuel Pressure Regulator?

In most cases, if you have tested the fuel pressure regulator, but eventually it fails, then replacing it is the best option. Depending on the make and model of the vehicle, the price ranges from $150 to over $1,000.

The price of the part itself is between $50-$400, and if the only replacement is the fuel regulator, it only takes one hour ($50-$100 per hour).

However, the average cost of replacing the fuel pressure regulator is about $250.

What is this compared to ignoring it? Therefore, please pay attention to any of the above symptoms to ensure that you find them as soon as possible.

fuel pressure regulator


What are the Risks of Ignoring Fuel Pressure Regulator Failure?

No matter how mild the symptoms seem, what happens behind the scenes is harmful to your engine.

The fuel regulator obtains data from the ECM connected to almost all other systems. Then, the sensor running the fuel regulator will receive the incorrect data and relay it back to the ECM, making all the data out of sync.

Then, you may encounter problems that may cause the car to behave differently and/or compromise safety. These include tempering, insufficient power, inability to start, and gas leakage.

fuel pressure regulator

How Do you Maintain the Fuel Pressure Regulator?

One of the best ways to ensure the long life of the fuel regulator is to replace the fuel filter every two years or 30,000 miles. Another method is to only refuel at top gas stations whose average gasoline quality is higher than other gas stations.

After all, it could be worse

If you find that the fuel pressure regulator is malfunctioning, there are several options. Test it yourself or take it to the store for testing. Then you can decide to buy the parts yourself and replace them yourself or let them do it.

In any case, as long as you deal with it in time, a bad fuel pressure regulator is not the end of the world.

Leave a Reply

Your email address will not be published. Required fields are marked *