Replacing A Fuel Pump: Is It Worth The Hassle?

Changing a fuel pump can be a challenging task, and it's important to know what you're doing to avoid causing further issues. A fuel pump is a critical component of a car's operation, transferring fuel from the tank to the engine. While fuel pumps are designed to last a long time, they can fail due to defects or other issues. Some signs of a failing fuel pump include difficulty starting the car, sudden loss of power, rough running or stalling, and strange noises coming from the fuel tank area. If you suspect your fuel pump needs replacing, it's best to consult a qualified mechanic or dealership. The cost of replacing a fuel pump can vary depending on the vehicle, age, and location, but it typically involves parts and labour costs. It's important to note that fuel vapours are highly flammable, so changing a fuel pump should be done with caution and in a well-ventilated area.

How hard is it to change a fuel pump?

The cost of replacing a fuel pump

So, the total cost of replacing a fuel pump can be anywhere from £100 to well over £1,500. For example, one person reported paying a total of £520 to replace their fuel pump, with £275 for the pump and £225 for labour. Another person was quoted £600-£700 for the replacement, which they said was reasonable for a dealership.

If you are mechanically-minded, it is possible to replace a fuel pump yourself, which will save on labour costs. However, it is important to note that this job can be challenging and may require specialised tools. It is also crucial to take proper safety precautions when working with flammable liquids.

Signs of a faulty fuel pump

A fuel pump is an essential component of your car's engine, delivering fuel from the tank to the engine. While fuel pumps are durable, they are not indestructible and will need to be replaced at some point. Here are some signs that your fuel pump is faulty and needs to be replaced:

Difficulty Starting the Car

A faulty fuel pump may cause difficulty in starting your car. This could manifest as a sputtering or stuttering start, as if the engine is only getting a trickle of fuel instead of the amount it needs.

Sudden Loss of Power While Driving

While driving, you may experience a sudden loss of power if your fuel pump is faulty. This could be in the form of stuttering, stumbling, or the engine not being able to take the throttle.

Engine Overheating

A failing fuel pump may cause your engine to overheat due to its inefficiency. The vehicle may operate for a short period, but then stop, and you may need to wait for it to cool down before it runs again.

Strange Noises

A faulty fuel pump may cause strange, high-pitched whining noises coming from the fuel tank area. This is due to the electric motor in the pump heating up and its output dropping off.

Stalling

A bad fuel pump can cause your car to stall during operation. The car may stall and then restart after several minutes, indicating that the fuel pump is overheating, possibly due to being operated with low fuel in the tank.

"Check Engine" Light Illuminating

The "Check Engine" light coming on can be a sign of a faulty fuel pump. This warning light can accompany any of the other issues mentioned above.

If you notice any of these signs, it is important to have your vehicle checked by a professional mechanic as soon as possible. A malfunctioning fuel pump can lead to bigger and more expensive problems if left unattended.

How to test for a faulty fuel pump

Testing for a faulty fuel pump can be done through a series of steps, from basic checks to advanced tests. Here is a detailed guide on how to identify a faulty fuel pump:

Part 1: Check Whether the Problem is Fuel-Related

If your engine won't start or is exhibiting performance issues, there are several initial checks you can perform:

• Listen for the Fuel Pump: Place your ear near the fuel tank and turn the ignition key to the "on" position. A properly functioning fuel pump should be audible.
• Whack the Fuel Tank: Ask an assistant to crank the engine while you hit the fuel tank with a rubber mallet. If the vehicle starts, it indicates a temporary issue with the electric motor inside the pump.
• Use Starter Fluid: Caution: This procedure carries a risk of personal injury and engine damage. If you choose to attempt this test, ensure you have safety equipment, including a fire extinguisher and safety glasses. Do not use starter fluid on a diesel engine. Try to start the vehicle by spraying starter fluid into the throttle body while an assistant cranks the engine. If the engine starts momentarily, it suggests a fuel-related problem, possibly a bad pump.

Part 2: Advanced Tests

If the engine won't start or is experiencing performance issues, you can perform the following advanced tests:

• Check for Diagnostic Trouble Codes (DTCs): Some vehicles will set DTCs in the car's computer when the fuel pump is faulty. Use a scanner or code reader to retrieve these codes. Many auto parts stores offer free code-pulling services. Additionally, inexpensive code-reading tools and smartphone apps are available.
• Check Fuel Trim with a Scan Tool: If the engine is running, check the short-term fuel trim (STFT) reading on a scan tool. Typically, fuel trim readings should be between -10 and 10, although this may vary depending on the vehicle. If the fuel trim is above 10, it suggests the engine is running lean, indicating a potential issue with the fuel pump.
• Check Fuel Pressure and/or Volume: Connect a fuel pressure gauge to the test port on the fuel rail and turn the ignition to the "on" position. Compare the reading to the specification in your vehicle's repair manual. If the reading deviates significantly, it may indicate a faulty fuel pump. Additionally, check if the pressure holds as per the factory repair information.
• Check Fuel Volume: Measure the fuel volume delivered by the pump using a fuel pressure gauge. Consult your repair manual for specific instructions and specifications.

Part 3: Before Condemning the Pump

Before concluding that the fuel pump is faulty, consider checking the following:

• Fuel Pump Electrical Circuit: In older continuous-style fuel systems, the fuel pump is controlled by the engine control module (ECM) via a relay. Check this relay before condemning the fuel pump. In newer returnless fuel systems, the fuel pump control module (FPCM) controls the pump based on sensor information. Ensure that the control system is functioning correctly.
• Fuel Pressure Regulator: On continuous fuel systems, check the regulator by disconnecting the attached vacuum hose and observing whether the pressure increases. If it doesn't, either the regulator or the vacuum supply may be faulty.
• Fuel Filter: Rather than testing the fuel filter, consider installing a new one, as it is relatively easy to replace. Remember to relieve the fuel system pressure before replacement.

Part 4: Very Advanced Tests

For those with access to advanced equipment, the following tests can be performed:

• Measure Current Draw with an Oscilloscope: Connect a low amp clamp probe to the pump's power wire and observe the waveform pattern. A properly functioning pump should produce a pattern of even "humps." Jagged and uneven humps suggest internal pump issues.
• Use a Professional-Grade Scan Tool: Some high-end scan tools allow remote fuel pump testing. By pressing a few buttons, you can activate the pump to see if it runs.

How to replace a fuel pump

Step 1: Identify the Problem

Firstly, you need to be sure that the fuel pump is faulty. Some common symptoms of a malfunctioning fuel pump include difficulty starting the car, sudden loss of power while driving, a rough run or stalling, strange high-pitched whining noises coming from the fuel tank area, and the "check engine" light illuminating on the dashboard.

Step 2: Prepare Your Tools and Workspace

Before getting started, gather all the necessary tools and equipment, including a new fuel pump, fuel filter, and any other components specific to your vehicle. It is also recommended to have an assistant to facilitate the process. Ensure you are working in a well-ventilated area, preferably outdoors, to minimise the risk of fire or inhaling harmful fumes. Wear safety glasses, gloves, and appropriate clothing to protect yourself from fuel spills and splashes.

Step 3: Reduce Fuel Level and Disconnect Battery

If possible, drain or siphon out most of the fuel from the tank to reduce the risk of spills and make the fuel tank lighter and easier to handle. Then, disconnect the negative battery cable.

Step 4: Locate and Access the Fuel Pump

The fuel pump is usually located inside the fuel tank, so you will need to remove the fuel tank from the vehicle. This process varies depending on the vehicle model. In some cases, you may be able to access the fuel pump through an access port under the rear seat or in the trunk area.

Step 5: Remove the Old Fuel Pump

Take note of the fuel line connections and wiring before removing the old pump. Remove all the connections, turn the large lock nut to free the old pump, and pull it out.

Step 6: Install the New Fuel Pump

Compare the new fuel pump with the old one to verify that you have the correct part. Install the new fuel pump by connecting the fuel lines and securing it in place.

Step 7: Reassemble and Test

Reassemble the fuel system by reconnecting the filler tube hose and the electrical connector. Reconnect the negative battery cable and fill the tank with fuel. Conduct a road test to confirm that the new fuel pump is functioning properly.

Additional Tips:

• Clean around the fuel pump before removing the old one to prevent dirt and debris from falling into the fuel tank.
• When replacing the fuel pump, consider replacing related components such as the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket.
• Refer to your vehicle's service manual or online tutorials for specific guidance on fuel pump replacement for your particular vehicle model.

Safety precautions when replacing a fuel pump

Replacing a fuel pump can be a challenging task, but with the right precautions, it can be made safer. Here are some safety precautions to follow when replacing a fuel pump:

Work in a Well-Ventilated Area

Fuel vapours are highly flammable and toxic. Ensure that you work in a well-ventilated area, preferably outdoors, to minimize the risk of fire or inhaling harmful fumes.

Use Proper Safety Gear

Always wear safety glasses, gloves, and appropriate clothing to protect yourself from fuel spills and splashes.

Drain the Fuel Tank

If possible, drain or siphon out most of the fuel from the tank to reduce the risk of spills and make the fuel tank lighter and easier to handle.

Clean Around the Fuel Pump

Before removing the fuel pump, clean the area around it to prevent dirt and debris from falling into the fuel tank.

Disconnect the Battery

Before starting any work on the fuel pump, be sure to disconnect the battery to reduce the risk of electrical shocks or sparks that could ignite fuel vapours.

Relieve the Fuel System Pressure

This can be done by running the engine and then pulling the fuel pump relay, causing the engine to stall. Alternatively, with the engine off, press the Schrader valve on the pressure line momentarily to release the fuel pressure.

Consult Vehicle Manual or Seek Professional Help

If you are unsure about any steps or procedures, it is important to consult your vehicle's service manual or seek the help of a professional mechanic. Fuel pump replacement can be complex, and it is always better to be safe than sorry.

Frequently asked questions