How To Decide Whether To Change Your Fuel Pump Yourself

Replacing a fuel pump is a moderately complicated task that can cost anywhere from $750 to $1,300. While it is possible to replace your own fuel pump, it is a dangerous job that requires dealing with high-pressure fuel lines and the transfer of gallons of gasoline. It is therefore strongly recommended that you use a professional mechanic for this job, as they are better equipped to handle any potential safety issues.

Warning signs your fuel pump needs replacing

A fuel pump is important for your car, and while your vehicle can sometimes limp along with a malfunctioning fuel pump, it is not good for your vehicle to drive with a poorly performing fuel pump. A fuel pump pumps fuel from your vehicle’s tank to the engine, so if it malfunctions, your engine will receive less fuel than it needs.

One of the most obvious symptoms of a faulty fuel pump is that your car may not start at all, or it might start poorly. This poor start will be characterised by a sputtering, stuttering, stammering sort of start, as if your car’s engine is only getting a trickle of fuel instead of the amount it needs. Your car may also stall during operation because the fuel pump is bad.

A damaged fuel pump might also make a loud, whining sound that you’ll hear from your gas tank. The pump may also make this noise if you’re low on fuel or the fuel in your tank is contaminated. The normal noise your pump makes is a low hum, so loud whining indicates there is a problem.

If your vehicle loses power when you drive up steep inclines or load it up with cargo, your fuel pump could be the culprit. As with faster speeds, the engine requires more gasoline to operate under stress. You’ll lose power if the pump isn’t working properly.

If your fuel pump is pushing too much fuel into the engine, you’ll notice power surges while you drive, i.e., speed spikes and drops. This will lead to lower fuel efficiency, as you will burn more gas than normal and have to make more trips to the gas station.

Finally, if your engine is getting gas from the pump, even a lesser amount than needed, it won’t likely stall. It will stall, however, if the pump causes your engine to overheat. An old and worn pump motor may get too hot and this can overheat your entire engine.

How to test for a faulty fuel pump

There are several ways to test for a faulty fuel pump. Firstly, you should verify if the problem is fuel-related. If the engine won't start, listen for the fuel pump by putting your ear near the fuel tank and turning the ignition key to the "on" position. If the fuel pump is working, you should hear an audible noise.

If the engine is not starting, you can try to "whack the tank". This involves having an assistant crank the engine while you hit the fuel tank with a rubber mallet. If the vehicle starts during this procedure, it indicates that the electric motor inside the pump is faulty.

Another method is to use starter fluid. Warning: this procedure can be dangerous and may cause personal injury or damage to your engine. If you decide to attempt this test, do so at your own risk and ensure you have the proper safety equipment, such as safety glasses and a fire extinguisher. To perform the test, remove the air intake and spray starter fluid into the throttle body while an assistant cranks the engine. If the engine starts and runs momentarily, the problem is fuel-related and may be due to a bad pump.

If the engine won't start or is exhibiting performance problems, you can check for diagnostic trouble codes (DTCs) with a scanner or code reader. A faulty pump may set DTCs in your car's computer, which could be directly related to the fuel pump or indicate an air/fuel ratio problem. Many auto parts stores will pull codes for free, and there are also inexpensive code-reading tools and smartphone apps available.

You can also check the fuel trim with a scan tool. This test only applies if the engine is running. Scan tools will display a data parameter called short-term fuel trim (STFT), which should typically be between -10 and 10, although this may vary depending on the vehicle. If the fuel trim is above 10, the engine is running lean, and the fuel pump may not be delivering enough fuel. However, other factors such as vacuum leaks can also cause a lean condition, so further testing is needed to confirm a faulty fuel pump.

Checking the fuel pressure and/or volume is another way to determine if there is a problem with the fuel pump. This will tell you if enough fuel is making it from the tank to the engine. However, this does not necessarily mean the pump is bad, as there could be other issues in the fuel pump circuit or problems such as a clogged fuel filter or bad pressure regulator. Before performing this test, ensure you relieve the fuel system pressure as outlined in your repair manual, and have safety glasses and a fire extinguisher nearby. Most modern vehicles have a test port located on the fuel rail, making it easy to connect a mechanical fuel pressure gauge, which is inexpensive and readily available. Turn the ignition to the "on" position (key on, engine off) and compare the reading on the gauge to the specification in your repair manual. If the reading varies significantly, you may have a bad fuel pump.

Additionally, when performing a static fuel pressure test, you can check if the pressure holds. The factory repair information will specify how long the fuel pressure should hold once the pump is turned off, which is usually several minutes. If the pressure bleeds off too quickly, there is a fuel-related problem, such as a bad pump check valve or faulty regulator.

For a more in-depth assessment, you can check the fuel pressure at idle or under load, or perform a "dead head" pressure test on continuous fuel systems (this test does not work on newer returnless systems with the regulator in the tank).

You can also check the fuel volume, as a pump may produce adequate pressure but not create enough volume. This can be done using a fuel pressure gauge to measure the volume. Connect the gauge and place the bleed end of its hose into a clean container. Activate the pump for 15 seconds while holding down the relief valve on the tool without starting the engine. Typically, a pump should deliver about a pint of fuel during this time, but consult the repair information for the exact procedure and specifications for your vehicle.

Before condemning the pump, there are a few other things you should check:

• The fuel pump electrical circuit: In older continuous-style fuel systems, the engine control module (ECM) controls the fuel pump via a relay. Check this relay before assuming the fuel pump is faulty. In newer returnless fuel systems, the fuel pump control module (FPCM) directly controls the fuel pump using information from sensors such as the fuel pressure and temperature sensors. Ensure everything within the control system is working properly. For both continuous and returnless systems, check the integrity of the wiring in the pump circuit with a digital multimeter (DMM) to test for continuity, power and ground, and any unwanted excessive resistance.
• The fuel pressure regulator: Returnless fuel systems do not have an external pressure regulator. However, on continuous systems, you can check the regulator by disconnecting the attached vacuum hose and seeing if the pressure increases. If the pressure does not increase, either the regulator is faulty or there is not an adequate vacuum supply.
• The fuel filter: Continuous fuel systems have an external filter that is relatively easy to replace. Rather than testing the filter, it may be easier to install a new one and see if that solves the problem. Remember to relieve the fuel system pressure before replacing the filter and have safety glasses and a fire extinguisher nearby.

For more advanced testing, you can use an oscilloscope and a low amp clamp probe to test the fuel pump. Connecting the probe to the pump's power wire provides a waveform pattern that can indicate internal pump problems. A good pump should produce a pattern of even "humps", while a bad pump will show jagged and uneven humps. A missing wave in the pattern usually indicates a burned-out winding or an open circuit, while waves that vary in shape and size suggest worn brushes and commutators.

Finally, some high-end scan tools allow remote fuel pump testing. By pushing a few buttons on the tool, you can activate the pump to see if it runs.

If you determine that you have a faulty fuel pump, it is important to get it replaced as soon as possible. Driving with a bad fuel pump can cause poor fuel efficiency, stalling, and engine damage, potentially leading to a bigger repair bill.

Cost of replacing a fuel pump

The cost of replacing a fuel pump varies depending on the vehicle, the mechanic, and the region. The average cost for a fuel pump replacement is between $750 and $1,321. The parts cost of a fuel pump is usually between $75 and $600, depending on the vehicle. Labor costs are estimated to be between $168 and $700.

If you are replacing the fuel pump yourself, the only additional cost is your time. Replacing a fuel pump is considered an intermediate-level task. If you decide to go with a professional, you may be looking at a cost of between $400 and $700. The replacement can take anywhere from 1 to 6 hours, depending on the expertise of the mechanic and the tools they have.

It is important to keep in mind that the cost of replacing a fuel pump can vary depending on the vehicle. For example, the average cost of a fuel pump replacement for a Chevrolet Tahoe is between $764 and $900, while the average cost for a Honda Civic is between $651 and $750.

Additionally, there may be related repairs that are needed, and taxes and fees will also add to the total cost. It is always a good idea to get an estimate from a trusted mechanic or repair shop to get an accurate idea of the cost of replacing a fuel pump in your specific vehicle.

How to replace a fuel pump

Warning Signs

A faulty fuel pump may cause your car to struggle to maintain speed, the engine to overheat, or the car to sputter. A faulty pump can also cause sudden power loss, which could be dangerous. Other warning signs include:

• Difficulty starting the car
• Loss of power while driving
• Stalling
• High-pitched whining noises from the fuel tank area

Preparation

Before starting, ensure you have all the necessary tools and a new fuel pump, fuel filter, and any other components specific to your vehicle. It is also recommended to reduce the fuel in the tank to minimise the risk of spillage. Work in a well-ventilated area, preferably outdoors, and wear safety gear such as glasses, gloves, and appropriate clothing to protect yourself from spills.

Step-by-Step Guide

• Relieve the pressure in the fuel system.
• Access the top of the fuel tank. You may need to remove the rear seats or lower and remove the fuel tank from the vehicle.
• Undo the electrical connectors and pump lines.
• Loosen the module retaining ring, remove the assembly, and take out the module from the tank.
• Install a new seal on the fuel tank.
• Fit the new module and tighten the retaining ring.
• Reassemble the fuel system and test the new fuel pump.

Tips

• Use a comprehensive toolkit, including a floor jack, fuel pressure gauge, large adjustable pliers, and screwdrivers.
• Consult your vehicle's service manual or online tutorials for specific instructions for your car make and model.
• Consider replacing related components such as the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket.

What is a fuel pump?

A fuel pump is a crucial component of a car's engine, responsible for transferring fuel from the gas tank to the engine. It ensures a smooth flow of fuel, enabling the engine to function optimally. Without a functional fuel pump, the engine will not receive the required amount of fuel, leading to performance issues and, eventually, a complete breakdown.

There are different types of fuel pumps, each designed to work with specific engine configurations and fuel types. The most common types are mechanical and electric fuel pumps. Mechanical fuel pumps, commonly found in older cars with carburetors, are typically mounted on the engine and use a diaphragm or plunger mechanism to transfer fuel. They operate at lower fuel pressures, usually between 10 and 15 psi.

On the other hand, modern fuel-injected cars predominantly use electric fuel pumps, which are located inside the fuel tank. These pumps create positive pressure to force fuel through the lines to the engine. By submerging the pump in fuel, it remains cool and well-lubricated, prolonging its lifespan. Electric fuel pumps are also advantageous as they can be placed anywhere between the engine and the fuel tank, providing flexibility in vehicle design.

The choice between a mechanical and electric fuel pump depends on the engine's fuel injection system. Carbureted engines often use low-pressure mechanical pumps, while fuel-injected engines typically employ electric pumps mounted inside the fuel tank for lower-pressure manifold injection systems. High-pressure direct injection systems, on the other hand, may use high-pressure mechanical pumps mounted directly on the engine.

In summary, a fuel pump is an essential component in a liquid-fuelled engine, responsible for ensuring a consistent fuel supply to the engine. Its specific type, placement, and operating pressure depend on the engine's design and fuel injection system. Regular maintenance and timely replacement of the fuel pump are crucial to prevent performance issues and unexpected breakdowns.

Frequently asked questions