Signs of a Faulty Car Fuel Pump: Here’s When You Should Replace It

The fuel pump in your car plays an important role in the fuel combustion process as it functions to supply fuel to the engine to ensure proper combustion. A faulty fuel pump could cause your car to lose power and accelerate erratically which could lead to an accident. If left unsolved, it could even cause severe damage to other parts of your engine. By knowing what to look out for when diagnosing a faulty fuel pump, you can know when to replace your fuel pump and prevent costly engine damage.

fuel pump

What Does a Fuel Pump Do?

In most vehicles, the fuel pump is located in the fuel tank, and it’s a vital component that delivers a steady amount of fuel from the tank to the engine. With the help of sensors, fuel pumps in modern vehicles are able to adjust the amount of fuel that is sent to the engine. This ensures that your engine produces enough power when you need it while also being more efficient.

Modern vehicles are equipped with electric fuel pumps while older vehicles have mechanical pumps. In your car, the fuel is pumped from the tank, through the fuel filter, and into the fuel rail, before the injectors spray it into the engine cylinders. Here are the different types of fuel pumps used in cars.

1. Mechanical Fuel Pump

Mechanical fuel pumps are found in older cars and have a simpler construction. This type of pump utilizes the energy produced by the engine to move a diaphragm on the exterior of the pump which creates a pressure difference (also called a positive displacement) that pushes the fuel out of the tank. Since most issues with a mechanical fuel pump are related to the diaphragm, they tend to be easier to identify and fix.

2. Electric Fuel Pump

An electric fuel pump is located in the fuel tank and uses an electromagnetic motor to push the fuel to the engine. Compared to a mechanical pump, an electrical one has more components making it more difficult to diagnose and fix. Below are the types of electric fuel pumps commonly used in vehicles.

  • In-tank pump: Most modern vehicles use in-tank pumps. Since the pump is located in the fuel tank, it has better protection against shock and extreme temperatures.
  • Inline pump: This type of pump is located between the fuel tank and engine, either below the car or on the fuel rail in the engine. Since it’s not located in the fuel tank, an inline pump is easier to replace than an in-tank one.
  • Rotary vane pump: A rotary vane pump works in the same way as a mechanical pump in that it uses positive displacement to deliver the fuel. The pump has a rotor, which is mounted eccentrically (off-center) inside the pump. When the blades rotate in the rotor, fuel is pushed out of the pump.

rotary vane pump animation

How a rotary vane pump works [Source: Giphy]

  • Gerotor pump: A gerotor pump also uses positive displacement principle but has different components. It has two interlocking gears – an internal drive gear and an external driven gear. As the two gears rotate, they produce a positive displacement at the discharge port which pushes the fuel out.

gerotor pump animation

How a gerotor pump works [Source: pumpschool.com]

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Signs of a Faulty Fuel Pump

Although mechanical and electrical fuel pumps have different components, they both produce similar symptoms when they are faulty. If you notice the signs below while driving, it’s time to check your fuel pump as it’s highly likely that your pump may be malfunctioning.

Loss of Power during Acceleration

Accelerating, especially from a standstill state, requires a lot of power and generally forces a car’s fuel pump to work harder to deliver more fuel to the engine. If you notice that your car is sluggish when accelerating, it could be a sign that your fuel pump is unable to keep up with the engine’s demand.

Car Jerking at High Speeds

When your fuel pump is unable to supply enough fuel to the engine while driving at high speeds, it causes an imbalance in the fuel-to-air ratio in the engine. This can cause the engine to skip several power strokes, which is when the engine pistons are pushed down in the cylinder as a result of fuel combustion. The power stroke rotates the crankshaft and wheels which then propel the vehicle forward. As a result of the skipped power strokes, your car might jerk at high speeds.

Car Struggling when Climbing up Hills or Carrying Cargo

Driving up a hill or carrying heavy loads will cause your engine to burn more fuel but if your fuel pump is unable to supply enough fuel, the engine won’t be able to produce enough power. If left unchecked, this could cause your car to stall putting you in a dangerous situation.

Read More: Signs of a Faulty Gearbox

Your Car Is Unable to Start

Your engine requires fuel even during start-up, so if you can’t start your car, it could have a faulty fuel pump. To confirm if this problem is caused by the fuel pump, you can check the pressure in the fuel line with a fuel pressure gauge. 

If the reading is zero, your fuel pump is most likely not working. Other than a faulty fuel pump, issues with the spark plugs, battery, alternator, or fuse box could also prevent your car from starting up, so it’s worth getting a professional mechanic to do a proper inspection.

Sudden Increase or Decrease in Engine Speed (Surging)

Surging happens when your engine speed suddenly goes up or down even when you hold the pedal down steadily. A faulty fuel pump can cause an engine surge when it doesn’t maintain consistent pressure in the fuel line. If you notice surging in your engine, it’s a sign that the fuel pump is unable to produce enough pressure consistently.

Signs of a Faulty Fuel Pump Relay

A fuel pump relay is usually located in the fuse box in the engine bay. It functions as the switch that controls the power supplied to the fuel pump. If the relay is faulty, your fuel pump might not be getting the power it needs and therefore will not function as it should.

Difficulty Starting Your Engine

A faulty fuel pump relay can cause the pump to stop sending fuel to the engine. When that happens, you may not be able to start your engine. However, as mentioned above, issues with starting your car can be caused by other problems, so it’s best to have a professional check your car.

Engine Performance Issues 

The fuel pump relay may stop functioning all at once or gradually. If the relay fails slowly, you might notice your engine performance drop gradually or occasionally. This can cause your engine to stall on occasion.

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carsome petrol refuel

Useful Things to Know About Your Car Fuel Pump

Besides knowing the signs of a faulty fuel pump, you should also understand how to maintain it and when to replace it. These tips can help you prolong the life of your fuel pump and help you be prepared for unexpected issues with your pump.

When Should You Replace Your Fuel Pump?

Like other vehicle components, a fuel pump goes through regular wear and tear. That being said, it can generally last over 150,000 kilometers before showing signs of wear.

How to Maintain Your Car Fuel Pump?

There are a couple of things you can do to prolong the life of your fuel pump, including:

  • Replacing the fuel filter according to the manufacturer’s recommendations: A dirty or clogged fuel filter creates extra pressure in the fuel line. This increased pressure can strain the pump and speed up wear and tear.
  • Fill up your tank with enough fuel: Since most fuel pumps are in-tank pumps, they rely on the fuel to keep them cool. If you leave your fuel on low for too long, it could cause your fuel pump to heat up and become damaged.

How Much Does It Cost to Replace a Fuel Pump?

A fuel pump is a relatively affordable component to replace ranging in price from RM50 to well above RM300. For instance, a fuel pump for older cars such as a Proton Wira or Waja could start from RM50, while a Perodua Myvi fuel pump typically costs RM150 and above. However, the price varies depending on the model and year of the car, as well as the brand of the pump.

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