Fuel Pump Vs Fuel Sensor: Which One Should You Choose?

Whether you should replace your fuel pump or fuel level sensor depends on the make and model of your car, the cost of the replacement parts, and how much you're willing to spend. If your fuel gauge is faulty, it could be due to a faulty fuel level sensor or fuel pump. In some cars, the fuel level sensor is attached to the fuel pump, so you may need to replace the entire fuel pump assembly.

The cost of replacing a fuel level sensor or fuel pump can vary depending on the car and the mechanic. Some people have reported being quoted prices ranging from $190 to $700 for the job. It is possible to replace a fuel level sensor yourself for under $100, but it is a complex and time-consuming process that requires removing the fuel tank and disconnecting various electrical and fuel lines.

Before replacing the fuel level sensor or fuel pump, it may be worth trying to clean the sensor or use a fuel system cleaner additive in your tank, as this has been known to fix the issue in some cases.

Fuel level sensor vs fuel gauge: what's the difference?

A fuel level sensor is a device installed inside a fuel tank to measure the accurate fuel level in real time. The sensor is usually mounted within the fuel tank or reservoir and employs a variety of measurement techniques to determine the fuel level. The core principle involves translating the position of a fuel tank's liquid level into an electrical signal that can be interpreted by the vehicle's instrumentation.

On the other hand, a fuel gauge is the calibrated display that shows the fuel level to the driver. It is typically connected to an electrical circuit that includes the fuel gauge on the dashboard. As the fuel level in the tank changes, the electrical signal is altered, and the digital gauge reflects this change.

There are several types of fuel level sensors, including capacitance, ultrasonic, resistive or float, and magnetic or Hall effect sensors. Capacitance sensors have two electrodes immersed at either end of the fuel tank, and the capacitance between them changes as the fuel level changes. Ultrasonic sensors emit sound waves towards the fuel surface and measure the time it takes for them to reflect back to determine the distance and, consequently, the fuel level. Resistive or float sensors use a float connected to a variable resistor; as the float moves with the changing fuel level, the resistance changes, resulting in a change in voltage. Magnetic or Hall effect sensors detect changes in the magnetic field to determine the fuel level and offer accurate, non-contact measurements.

While a fuel level sensor is responsible for measuring and transmitting fuel level data, a fuel gauge is the display unit that presents this information to the driver. The sensor's electrical signal is sent to the fuel gauge, which calibrates and displays the fuel level accordingly.

When to replace your fuel pump

A fuel pump is a crucial component of your vehicle, delivering fuel from the tank to the engine. Usually, fuel pumps are reliable and long-lasting, but sometimes they need to be replaced. Here are some signs that indicate when it's time to replace your fuel pump:

• Inability to maintain speed: You may experience your engine "choking" or struggling to maintain speed, even though the fuel gauge indicates there is enough fuel in the tank.
• Engine overheating: A failing fuel pump may overheat, and due to its inefficiency, cause the engine to overheat as well. This type of failure may cause the vehicle to operate for a short period (around 15-30 minutes) before stopping.
• Sputtering and noises: Noises, backfires, and sputtering engines are signs of a faulty fuel pump. Typically, electronic fuel pumps won't make a noise unless they start to fail. An inconsistent fuel flow can cause internal engine problems and hesitation during acceleration.
• Engine light comes on: The "Check Engine" light on your dashboard may illuminate, indicating a potential issue with the fuel pump or another component.
• Engine not starting: If your vehicle is struggling to start or isn't starting at all, it could be due to a faulty fuel pump. This may be accompanied by the engine cranking but not turning over.
• Engine stalling: If your engine stalls or dies while driving, it could be due to a low-pressure fuel pump not providing enough fuel to the engine. This may be more noticeable during acceleration or when the vehicle is under stress, such as towing a heavy load or driving uphill.
• Engine surging: A faulty fuel pump may send too much fuel to the engine, causing the vehicle to surge. Surging means the vehicle will repeatedly pick up and then drop speed, even if you haven't touched the pedals.
• Whining noise from the fuel tank: Your fuel pump makes a low humming sound when running normally. If you notice a significant increase in the pitch of this sound, it could indicate a problem with the fuel pump.
• Decreased fuel efficiency: Poor fuel efficiency can be a sign of a bad fuel pump. Damaged components can allow excess fuel into the engine, leading to waste.

It's important to note that these symptoms may also be caused by other issues, such as bad fuel, damaged fuel lines, or a clogged fuel filter. Therefore, it's always recommended to have a comprehensive inspection and diagnosis performed by a qualified technician to accurately identify the root cause of the problem.

How to replace a fuel level sensor

A fuel level sensor, also known as a gasoline gauge, indicates the amount of gasoline left in a vehicle's tank. While you could pay a professional around $450 to install a new fuel sensor, it is possible to do it yourself for under $100. Here is a step-by-step guide on how to replace a fuel level sensor:

Step 1: Close the Gas and Power Lines

• Remove the negative battery cable.
• Open the trunk and remove the spare tire.
• Detach the gas and electric power cables from the fuel tank.

Step 2: Detach the Tank

• Unclip the electrical cables using a small screwdriver.
• Remove the tank holders and the bolts on the bearers that support the tank under the vehicle.
• With the help of another person, carefully lower the gas tank.

Step 3: Remove the Transmitting Device

• Remove the clips on the electrical attachment at the top of the transmitting device. Do not detach the gas pipe, as fuel will spill out.
• Using a screwdriver and hammer, rotate the lock ring to align the lock tabs and channels. Spray the lock ring with lubricating oil to reduce friction.
• Once the lock ring is off, remove the transmitting device from the gas tank.

Step 4: Remove the Fuel Level Sensor

• Locate the fuel level sensor at the bottom of the transmitting device.
• Remove the clip from the harness and slide off the sensor.

Step 5: Install the New Sensor

• Purchase the correct fuel level sensor for your vehicle by referring to the owner's manual or consulting a store associate.
• Slide the new sensor into the place of the old one.
• Reattach the transmitting device, the tank, and all cables and bolts, following the previous steps in reverse.

Note: If there is insufficient space to access the transmitting unit, you must first reduce the volume of fuel in the tank to around a quarter full.

How to replace a fuel pump

Firstly, it is important to note that replacing a fuel pump can be a challenging task, so if you are in doubt, it is best to consult a professional mechanic. However, if you are confident and would like to attempt the replacement yourself, here is a step-by-step guide to help you through the process.

Preparations:

• Gather all the necessary tools and equipment, including a new fuel pump, fuel filter, and any other components specific to your vehicle.
• Reduce the amount of fuel in the tank to minimise the risk of spillage and make the tank lighter and easier to handle.
• Ensure you have a safe and accessible workspace with good ventilation, preferably outdoors, to minimise the risk of fire and inhaling harmful fumes.
• Put on safety gear, including safety glasses, gloves, and appropriate clothing to protect yourself from fuel spills and splashes.

Step-by-Step Guide:

Relieve the Fuel System Pressure:

• With the engine running, pull the fuel pump relay, which will cause the engine to stall.
• Alternatively, with the engine off, press the Schrader valve on the pressure line momentarily to release a small spray of fuel.

Locate and Remove the Fuel Tank:

• The fuel pump is usually located inside the fuel tank.
• Depending on your vehicle, you may need to remove the fuel tank from the vehicle. This process can vary greatly, and you may need to use a jack to support and lower the tank.
• Some vehicles may have an access port under the rear seat or in the trunk area, which can make the process easier.

Remove the Old Fuel Pump:

• Before removing the old pump, take note of the fuel line connections and wiring.
• Disconnect all connections, turn the large lock nut to free the old pump, and pull it out.

Install the New Fuel Pump:

• Compare the new fuel pump with the old one to ensure you have the correct part.
• Reassemble the fuel system by connecting the fuel lines to the new pump.
• If you removed the fuel tank, lift it back into place, reinstall the retaining strap, and reconnect the filler tube hose and electrical connector.

Final Steps:

• Reconnect the negative battery cable.
• Refill the fuel tank.
• Conduct a road test to confirm that the new fuel pump is functioning properly.

Tips:

• Drain the fuel tank if possible to reduce the risk of spills and make it easier to handle.
• Clean around the fuel pump to prevent dirt and debris from falling into the fuel tank.
• Consider replacing related components such as the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket.
• Always consult your vehicle's service manual or online tutorials for specific guidance on tackling this task.

Remember, working with flammable liquids can be dangerous, so take your time, follow instructions carefully, and ensure your workspace is well-ventilated.

Cost of replacement

The cost of replacing a fuel pump and fuel level sensor can vary depending on several factors, including the make and model of your vehicle, the complexity of the repair, and the labour rate of the mechanic or repair shop.

In some cases, the fuel pump and level sensor may be integrated into a single unit, which can be more expensive to replace than a separate fuel level sensor. For example, one person reported being quoted $700 to replace the entire fuel pump assembly, while another mechanic quoted them $190 to replace just the fuel pump. The sensor alone was quoted at $382 by another shop.

For a 2015 Ford Focus, a Ford mechanic estimates the cost of replacing the low-pressure sensor to be between $150 and $300, while the fuel rail replacement would range from $600 to $1300.

If you are handy and have access to the necessary tools and knowledge, you may be able to replace the fuel level sensor yourself, which can significantly reduce the cost. One person reported that they were able to replace the sensor in their BMW E46 themselves, while another individual was advised to purchase a name-brand replacement for their 2007 Honda CR-V, which could be purchased for under $300.

It is important to note that attempting to replace the fuel level sensor yourself may void any warranties on your vehicle, and it is essential to work in a well-ventilated area due to the hazardous fumes associated with fuel.

Frequently asked questions