In order to keep your Mercedes in top condition, you need to be able to recognize when your vehicle is showing signs of needing repairs. When neglected, problems that may seem small at first can go on to cause a great deal of damage to your vehicle.
The fuel pressure regulator will usually show signs of malfunctioning before it completely fails, so it is important to have it taken care of promptly before it can cause greater damage to your vehicle’s engine.
Your Mercedes has an electronic fuel injection system, meaning the fuel is injected into the engine. The fuel pressure regulator is part of your vehicle’s fuel delivery system, and it controls the pressure of the fuel going to the engine, which also ensures the engine receives the correct amount of fuel.
In addition to the pressure and amount of fuel, the fuel pressure regulator helps balance the air to fuel ratio for optimal combustion performance. This is an essential function to keep your engine running smoothly and performing well.
The fuel pressure regulator consists of several different parts, including a diaphragm, bypass valve, spring, and inlet and outlet ports. Damaged or broken parts and seals are common causes for a failing fuel pressure regulator.
Signs Your Fuel Pressure Regulator Needs to be Repaired or Replaced
If the fuel pressure regulator is failing, it will be fairly easy to notice, because a number of functions on your vehicle will be affected. The following are signs that your fuel pressure regulator may need to be repaired or replaced:
- Poor Acceleration: This may be one of the first things you notice if your vehicle’s fuel pressure regulator is failing. No matter how hard you press on the gas pedal, the vehicle may hesitate or feel sluggish and not go as fast.
- Poor Deceleration: The engine may have problems decelerating too, because too much fuel in the engine can cause it to backfire. You may notice your vehicle takes a longer time to slow down.
- Decreased Fuel Efficiency: If the fuel enters the engine at too low of a pressure, then the engine will need to work extra hard, causing it to consume more fuel and decrease your vehicle’s gas mileage. If the fuel goes in at too high of a pressure, then there will be too much fuel and it will flood the engine, decreasing the engine’s fuel efficiency.
- Black Smoke from Exhaust: Your vehicle’s exhaust smoke can turn black if the fuel is sent to the engine at too high of a pressure, giving the engine more fuel than it needs.
- Leaking Fuel: If your vehicle is leaking fuel, you may notice brown fluid coming from your exhaust pipe, or you may smell fuel while inside your vehicle.
- Engine Misfires: The fuel pressure regulator helps maintain the engine’s air fuel ratio, so when it malfunctions, the ratio is thrown off, causing the engine to frequently misfire.
- Engine Won’t Start: If you rule out the more common causes for your vehicle’s engine to not start, such as a dead battery or faulty alternator, then it may be due to the fuel pressure regulator. Since the regulator is responsible for pushing fuel into the engine, if it is not performing properly, then the engine may have trouble turning on.
- Black Deposits on Spark Plugs: When there is too much fuel in the fuel-air mixture, then black carbon deposits may begin to accumulate on the spark plugs.
- Rough Idling: Your vehicle may shake, vibrate, and/or make unusual noises while idling.
- Check Engine Light Illuminates: The check engine light can indicate a number of different issues, so you may want to also look for other signs that your vehicle’s fuel pressure regulator is malfunctioning.
Hagan’s Motor Pool for Your Mercedes Upkeep
As 
Rochester’s leading full-service and pre-owned German auto dealership, Hagan’s Motor Pool is able to offer the highest quality service to German brand vehicles. Our technicians are experts with German auto brands, including Mercedes, and are committed to keeping them in top condition with a high performance.
Our veteran-owned shop serves customers from Alton, Barrington, Berwick, Dover, and Rochester, NH. If you are in the area, and your Mercedes is showing signs of needing a fuel pressure regulator repair or replacement, schedule an appointment with us today, and we will make sure your vehicle’s engine is running smoothly.