A faulty fuel pressure regulator is a ubiquitous part that causes a lot of engine problems.
But luckily, it’s not an advanced part to replace, you can often do it yourself, and it’s usually pretty cheap.
In this article, you will learn the most common symptoms of a faulty fuel pressure regulator and the cost of a fuel pressure regulator replacement.
Signs of a Bad Fuel Pressure Regulator
A faulty fuel pressure regulator means that the combustion process is disturbed and the engine does not produce enough power. There are some noticeable symptoms that would suggest that the problem is due to a poor fuel pressure regulator.
1. Engine Misfire / Loss in Acceleration
One of the first symptoms you will notice is that the engine starts to misfire and the acceleration will drop. If you drive at a constant speed, your car will stutter or slow down, then accelerate normally before repeating the process. This indicates that there may be a problem with the fuel pressure regulator.
2. Fuel Leakage
Another common symptom is fuel leakage, which not only causes performance problems but also leads to a bad smell. A fuel leak occurs when the diaphragm or seal of the fuel pressure regulator is damaged and fails. Fuel leakage is also dangerous and should be taken care of immediately.
3. Black Smoke from the Exhaust Pipe
Black smoke coming out of the car’s exhaust pipe may have various other causes, but if you see black or gray colored smoke and also notice other symptoms mentioned in this article, the problem is most likely with the fuel pressure regulator.
4. Spark Plug Covered with Black Debris
Soot is caused by the combustion of oil in the engine head. Check the end of your spark plug to see if black soot has settled. If so, your fuel pressure regulator is most likely damaged and you will need to replace both the fuel pressure regulator and spark plug.
5. Gasoline Leaks from Tailpipe
A faulty fuel pressure regulator will cause excess fuel to flow through the lines and overfill the exhaust system. As a result, gas starts to drip from the exhaust pipe.
6. Gasoline Filled in Vacuum Hose
A defective fuel pressure regulator causes the vacuum hose to be filled with gasoline. To check this, remove the vacuum hose connection to the fuel pressure regulator and check whether there is gasoline in the line. If so, you have a defective fuel pressure regulator.
7. Gasoline Smell from the Dipstick
Leakage due to a poor fuel pressure regulator can cause the oil reservoir to fill with gasoline. If you can smell gasoline on the dipstick, it means that your fuel pressure regulator has a problem.
8. Drop in Mileage
A faulty fuel pressure regulator will require your vehicle to use more fuel. As a result, you will notice a decrease in mileage, indicating that the fuel pressure regulator is damaged.
9. Check Engine Light
Almost all modern cars use a full-time monitoring system to constantly monitor the car sensors in the car engine. If one of these sensors fails, an error code is stored in the error code memory, and if this happens repeatedly, the check engine light is displayed on your dashboard.
What is a Fuel Pressure Regulator?
A fuel pressure regulator is a part of your fuel system. It is usually mounted on the fuel rail, but can also be mounted on the fuel return hose. The fuel pressure regulator is controlled by a small vacuum hose leading to the inlet. If there is negative pressure in the inlet when idling, it lowers the fuel pressure. If you have installed a turbocharger or compressor in your car, the fuel pressure will also increase with the boost pressure from the inlet.
There are two different types of fuel pressure regulators. One of them is linear, i.e. at 1 bar boost pressure, the fuel pressure is 1 bar higher. You can also have a progressive fuel pressure regulator in various forms, for example, a 1:1.5 regulator. This means that for every 1 bar of boost pressure, the regulator produces a 1.5 bar higher fuel pressure.
Why is it Important?
Since the fuel pressure regulator is directly responsible for distributing fuel to the engine, its proper maintenance is essential. Most fuel pressure regulators use mechanical diaphragms that are operated by a vacuum, and these diaphragms help to change the fuel pressure.
However, modern vehicles are equipped with an electronic fuel pressure regulator that works differently. Any problem with the fuel pressure regulator directly affects the performance of your engine. It is therefore important to ensure its maintenance.
Understanding Your Vehicle’s Fuel System
There are two basic types of fuel systems found in cars: a continuous return fuel system and a non-return fuel system.
The continuous return fuel system is usually found in old vehicles. It uses a fuel pump to pump the fuel from the tank to the fuel rail. The fuel pump delivers excess fuel, so a regulator is installed to maintain the correct pressure and return the extra fuel back to the tank. The fuel pressure regulator is controlled by the engine vacuum and is mounted on the fuel rail.
The non-return fuel system is found in modern cars, and it has no return channel to the fuel tank or an externally mounted fuel pressure regulator. In this system, the fuel pressure regulator is built into the fuel pump, which is controlled by the powertrain control module (PCM).
Diagnosing Fuel Pressure Regulator with a Fuel Pressure Gauge
The best way to check the fuel pressure regulator for leaks is with a fuel pressure gauge. This test checks whether the fuel pressure regulator regulates the line pressure appropriately according to changes in engine vacuum.
Let the engine run and disconnect the vacuum hose from the regulator. When the hose is disconnected, the pressure in the fuel system should increase by 8 to 10 psi. If there is no change, this means that the pressure regulator is defective and must be replaced.
On newer vehicles, the fuel pressure regulator can be conveniently checked with an OBD2 scanner in any garage or at home, but it is always a good idea to check it manually as well. If you are interested in an OBD2 scanner for use at home, you can take a look at our overview article: OBD2 scanner review.
If you do not have a fuel pressure tester at home but want one, you can check it out here on Amazon: Fuel pressure tester
Fuel pressure regulator Replacement Cost
The replacement cost of the fuel pressure regulator depends on the make and model of the vehicle. An average job requires between $260 and $320 for diagnosis and replacement. The actual part costs between $65 and $75, but labor costs are high because the mechanic needs a lot of time to do the job.
In modern cars, the fuel pressure regulator is checked electronically via the engine control unit and can also be conveniently fixed. Remember to bring your car for a checkup as soon as you notice any of these symptoms, as they can be dangerous.
- The fuel pressure regulator regulates the fuel pressure with negative pressure and boost. A linear fuel pressure regulator increases the fuel pressure by 1 bar per 1 bar boost pressure in the inlet.
- It is quite simple to test your fuel pressure regulator at home, but you need a fuel pressure tester.
- The replacement cost is often not very high for either the part or the replacement cost.
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