Common Problems After Changing Fuel Pump: Troubleshooting Fuel Pump Issues

So you just replaced your fuel pump and now your car is acting up- don’t worry, you’re not alone. Changing the fuel pump is a crucial component of the car’s fuel system, and if something goes wrong, it can cause your car to stall or even fail to start altogether.

After replacing a fuel pump, it’s essential to be aware of some common problems such as electric issues, fuel leakage, and issues with fuel pressures. In this post, I’ll draw from my experience and provide some straightforward tips to help you avoid or fix these issues. So, let’s dive in and get your ride back on the road!

So, what are the common problems after changing fuel pump? One of the most common problems after changing a fuel pump is a loss of power or acceleration. Another issue you might encounter is a rough idle or stalling. This can happen because the fuel pump is not providing enough fuel to the engine. Another propeblem after changing the fuel pump is a decrease in fuel efficiency. This decrease is caused by a faulty installation, which can lead to fuel leaks and a decrease in the pressure required for the engine to run efficiently. If you’re experiencing any of these problems after changing your fuel pump, the first step is to check for any diagnostic trouble codes (DTCs) using a code reader. This can help you pinpoint the exact cause of the issue and determine the best course of action for repair. 

Common Problems After Changing Fuel Pump

Here are some of the most common problems after changing fuel pump:

• Fuel leaks and fuel pressure problems
• Loose fuel pump
• Electrical issues
• Inconsistent reading on the fuel gauge
• Difficulty starting the engine or engine stalling
• Dust or Debris getting into the gas tank
• Engine Misfires
• Rough Idle
• Poor fuel economy
• Check engine light illuminated on the dashboard
• Accidentally pinching a fuel line
• Loud whining noise from the fuel tank

Key Takeaways

• The fuel pump assembly consists of a fuel pump (a small cylinder), float lever, fuel gauge sender, fuel pump casing, harness connector, gasket, and strainer.
• The fuel inside the tank should always be more than 1/4th of the fuel tank capacity. It will prevent the fuel pump from running dry, and also help keep it cool.
• While installing the fuel pump, make sure that you do not bend the fuel level float arm.
• Make sure that there are no sharp bends (pinch) in the fuel line after you change the fuel pump. It will prevent delivery of fuel at an optimum pressure.
• Make sure that you do not damage the wiring connection of the fuel gauge sending unit while installing the fuel pump.
• Make sure that the position of the float arm is in the same direction as that installed by the factory.
• Don’t forget to change the fuel filter when you change the fuel pump.
• Make sure there are no debris or metal shavings when you change the fuel pump. It will prevent the supply of fuel and cause difficulty in starting the car.
• In some vehicles, a fuel pump has a strainer on its inlet. If you’re only changing the fuel pump, make sure to install a new strainer at its inlet.
• Always check the fuse and relay of the fuel pump after you change it.
• Make sure that the harness connector that goes into the fuel pump is clean.
• Check for any fuel leaks after installing the fuel pump. You should also measure fuel pressure after changing the fuel pump. Moreover, you must follow instructions in the owner’s manual as the installation procedure of a fuel pump for each vehicle is different.
• Make sure that fuel hoses have clamps installed.
• Make sure that fuel hoses are not cut, pinched or collapsed.
• The harness connector of anew fuel pump assembly MUST be replaced, even if there are no issues with the old connector.

Importance of the Electric Fuel Pump in Car Operation

Earlier, fuel pumps were mechanical and were driven off of a camshaft in the engine. In modern engines with fuel injectors instead of carburetors, electrical fuel pumps are installed that delivers fuel from the fuel tank to the fuel injectors at a defined pressure. Electric fuel pumps in more modern vehicles are switched on by the ECU (Engine control unit) by sending electric signals.

In modern engines, an electric fuel pump runs for a couple of seconds when you just turn on the ignition. But, as the engine is started, the fuel pump runs constantly.

One big advantage of electric fuel pumps is that they maintain constant fuel pressure. This means that the fuel that is being sent to the engine is always at the right pressure, which helps the car start more easily. 

Another advantage of electric fuel pumps is that they reduce vapor lock problems. Vapor lock happens when gasoline in the fuel lines gets too hot and turns into vapor. Vapor lock form air pockets, which can disrupt the flow of fuel to the engine. This can cause the engine to stop working. But an electric fuel pump can prevent this from happening because it keeps the fuel moving through the lines at constant pressure.

Unlike mechanical fuel pumps, electric fuel pumps are usually located near the fuel tank in the rear of the vehicle, which allows them to keep the fuel cooler. The electric fuel pump continuously pumps fuel to the engine at a constant pressure and flow rate, which helps to keep the fuel from boiling and forming vapor. Moreover, since electric fuel pumps are submerged in the fuel inside the fuel tank, it also helps keep the fuel pump cooler.

A third advantage of electric fuel pumps is that they are not physically attached to the engine. This means that they don’t have to be the exact same size or shape as a mechanical fuel pump, which can be very useful if an exact replacement isn’t available.

In addition, worn cams on the camshaft do not affect electric fuel pumps. A cam is a part of the engine that helps the mechanical fuel pump work. If the cam gets worn out, the mechanical fuel pump does not rotate properly. But since electric fuel pumps don’t rely on cams, they don’t have this problem.

Finally, electric fuel pumps are easy to install a hidden on/off switch as an anti-theft precaution. This means that if someone tries to steal the car, they won’t be able to start it because the fuel pump won’t work.

Overall, electric fuel pumps have several advantages over mechanical fuel pumps, including maintaining constant fuel pressure, reducing vapor lock problems, and being easier to fit in a car.

What Can Damage Electric Fuel Pump?

One of the most common causes of fuel pump damage is running the vehicle on a low fuel level. When the fuel level is low, the fuel pump has to work harder to draw fuel from the tank. This can cause the pump to overheat, leading to reduced performance and eventual failure. If you have read my article on why a car sputters after getting gas, I have elaborated on how the fuel pump can experience fuel starvation.

In situations where the fuel delivery is insufficient or completely absent, the current consumption increases while the cooling process is effectively halted. As a consequence, gas accumulates within the pump, causing issues in the engine’s fuel supply and eventually leading to pump deterioration.

Another factor that can damage an electric fuel pump is contamination of the fuel system. Dirt, debris, and other contaminants can enter the fuel tank and make their way to the fuel pump, causing damage to the pump’s delicate internal components. 

Electrical issues can also damage an electric fuel pump. Over-voltage or under-voltage conditions can cause the pump’s motor to overheat, leading to premature failure. Additionally, corrosion or damage to the pump’s electrical wiring or connectors can cause intermittent or complete pump failure. 

Problems With Vehicle After Replacing Fuel Pump

Here are the problems your vehicle can face after replacing the fuel pump”

1. Electrical Issues

One common problem after replacing fuel pumps is faulty electrical connections, which is actually the second most frequent cause. Despite the fact that the fuel pump is fully functional and can deliver pressure and flow well within the standard range, a degraded output is observed as a result of poor electrical connections.

The fuel pump is usually connected to a fuse that protects the electrical circuit. If the fuse blows, the fuel pump won’t work, and you’ll experience similar symptoms to before replacing the fuel pump. To fix this issue, you’ll have to replace the blown fuse with a new one of the same amperage. You can find the location of the fuel pump fuse in your car’s owner’s manual.

A fuel pump connector can also cause intermittent electrical faults. A fuel pump’s connector is an essential component of a vehicle’s fuel system that needs to be checked and maintained regularly.

A poor electric connection of the fuel pump can occur when the connector’s pins become corroded or worn out, causing resistance in the fuel pump’s electrical circuit. The resistance restricts the amount of power reaching the fuel pump, which causes it to work harder and turn slower than it should. 

When a fuel pump rotates slower due to corroded electric connections, it will not generate suitable fuel pressure, resulting in rough idle or difficulty in starting a car.

When a fuel pump is forced to work harder than it should repeatedly, it can shorten its lifespan, making it weaker, less efficient, and eventually failing completely.

This can result in engine stumbling, as the fuel supply is disrupted leading to the engine temporarily losing power and then regaining it when the connection is restored. Consequently, this can lead to poor overall engine performance and reduced driving safety.

You can also use a new connector that comes with a pump assembly if the old connector is damaged.

Another possible electrical issue after changing the fuel pump is a faulty fuel pump relay. The relay is a small device that controls the flow of electricity to the fuel pump.

If the relay is faulty, the fuel pump might not receive enough voltage, or it might not work at all. To check if the relay is the problem, you can swap it with a similar relay in your car’s fuse box and see if the fuel pump works. If it does, then the relay was the issue, and you’ll need to replace it. 

You can read this guide to test the fuses and relays of a fuel pump. The method to test fuses and relays is the same for every electrical component.

Lastly, a short circuit can also occur while changing the fuel pump. This is because, during fuel pump replacement, some mechanics have a habit of disconnecting the negative terminal of the battery. If, by mistake, they have removed the positive terminal of the battery first, a short circuit could occur. Similarly, the positive terminal of the battery should be connected first. 

After fuel pump replacement, if the car does not even crank, it means that a short circuit has occurred in the electrical system of the vehicle.

Fixing issues for the connector of the fuel pump

Sometimes, you have to replace the new connector that comes with a fuel pump with the old connector. Now, this is a very tricky process as the color coding of the wires of a new pump connector can be different compared to that of the old one. If you don’t follow the color coding, it will result in the pump not starting, due to which your car will also not start after changing the fuel pump.

So, to install the old connector of the new fuel pump over the old connector, cut the wires to the desired length and slice the insulation up to certain length. After that, from the reference of the color code diagram of the new connector, match the vehicle wire colors and position to the replacement style connector.

You can watch the below video for a better understanding:

2. Dust Or Debris Getting Into The Gas Tank

One of the biggest problems that can arise after changing your fuel pump is the introduction of dust or debris into the gas tank. This can happen if the tank isn’t properly cleaned beforehand, or if the fuel lines and filters aren’t replaced along with the pump.

So why is dust or debris in the gas tank such a big deal? There are a few reasons:

1. Clogged Fuel Filters: When particles get into your fuel system, they can clog up your fuel filters. This can cause your engine to run poorly or even stall altogether.
2. Fuel Pump Damage: If debris gets into your fuel pump, it can cause damage to the internal components. This can lead to reduced fuel pressure and flow, which can cause engine performance issues.
3. Fuel Injector Damage: The fuel injectors in your vehicle are responsible for delivering fuel to the engine. If debris gets into these components, they can become clogged or damaged. This can cause rough idling, poor acceleration, and reduced fuel efficiency.

How to fix?

The best solution to prevent dust or debris from entering the gas tank is to be mindful of the type of gasoline you use.

Always use high-quality gasoline that is free of contaminants and has a good reputation. Additionally, avoid filling up the gas tank with old or dirty gasoline that has been sitting in the tank for too long.

During changing the fuel pump, make sure to rinse the entire fuel system with clean quality fuel.

3. Loud Whining Noise Of the Fuel Pump

As a vehicle owner, you may have experienced the frustration of a malfunctioning fuel pump. When this happens, you may need to replace the fuel pump, which can be a costly and time-consuming process. However, even after replacing the fuel pump, you may hear a loud whining noise that can cause problems.

Contaminated fuel and low fuel tank level are the possible causes of a whining noise of a new fuel pump that you have just replaced.

Contaminated fuel can damage your fuel pump and cause it to produce unusual sounds. Dirt, rust, and debris can enter your fuel tank through a clogged fuel filter, and eventually, find their way into the fuel pump.

The fuel pump is only designed to handle liquid. If dust, metal shavings and debris enter the fuel tank, they will cause the fuel pump to produce a loud whining noise. 

Another possible cause of a loud whining noise after changing your fuel pump is a low fuel tank level. When your fuel tank level is low, the fuel pump has to work harder to push fuel through the fuel system, which can result in a whining noise. 

The fuel keeps the fuel pump cool as well. If the fuel tank is empty, the fuel pump will wear out faster from excessive heat.

How it can cause other problems?

While a whining fuel pump might not seem like a big deal, it can actually lead to some serious problems down the line. Here are a few potential issues to be aware of:

• Reduced fuel efficiency: If the fuel pump isn’t working as efficiently as it should be, your car might start to burn more gas than usual. This can lead to increased fuel costs and a reduced driving range.
• Stalling or failure to start: If the fuel pump fails completely, your car won’t be able to start or will stall while you’re driving.

How to fix?

A good fuel pump only emits a soft humming sound which can be only audible if you open the gas cap and bring your ear close to it.

If the new fuel pump is producing a loud whining noise, you should check the filter at the inlet of the fuel pump if it is blocked by dirt and debris. 

In most vehicles, the fuel filter is after the fuel pump. But at the fuel pump inlet, there is a strainer to filter coarse particles. If the pump inlet is blocked, it will cause dry running of the fuel pump, resulting in stalling the engine and loud noise of the fuel pump.

Next, you should make sure that the fuel pump must be installed low (“wet”, below the fluid level) in the vicinity of the tank. The fuel level in the fuel tank should not be less than 1/4th of the fuel tank capacity.

4. Clogged Fuel Filter

Your fuel filter is responsible for ensuring your car’s fuel system is free of debris and contaminants that can damage your engine. Over time, the filter can become clogged with dirt, rust, and other particles. This can cause a drop in fuel pressure, which can lead to poor engine performance, reduced fuel efficiency, and engine stalling.

When you change your fuel pump, it’s essential to replace your fuel filter at the same time. This ensures that the new fuel pump is working correctly and that the fuel system is free of contaminants that can clog the filter.

If you haven’t changed your fuel filter in a while, it may be clogged with old, gunky fuel. Moreover, when you change your fuel pump, you may disturb debris that has settled at the bottom of your fuel tank. This debris can make its way to your fuel filter and clog it.

When the fuel filter is quite old and clogged with dirt particles, the fuel pump will have to work harder to push fuel through the fuel filter. As a result, it will shorten the life of a fuel pump.

How to fix?

While removing the fuel tank to change the fuel pump, make sure to take the time to clean the debris off the fuel tank.

5. Fuel Leaks and Pressure Problems After Changing Fuel Pump

One common problem that people encounter after changing their fuel pump is fuel leaks. Fuel leaks can be dangerous and costly if not addressed promptly. Moreover, if the fuel is leaking, it will not have sufficient pressure for an optimum fuel injection through the fuel injectors. As a result, the car will have difficulty in starting and accelerating.

One common cause of fuel leaks after changing a fuel pump is improper installation. If the fuel pump is not installed correctly, it can cause fuel to leak out. This can happen if the fuel pump is not tightened enough or if the fuel lines are not connected properly. 

When installing a new fuel pump, it’s important to tighten the bolts and fasteners to manufacturer specifications. If they are not tightened to the proper torque, these parts could loosen over time and cause a fuel leak.

Here, I would like to highlight that in all vehicles, the fuel pump is secured by a cam locking ring. Now, the way to secure a fuel pump with a cam locking ring is different for each vehicle.

In some vehicles, the fuel pump assembly comes with a metal cover that is tightened with nuts and fasteners. Such vehicles don’t need to have a cam locking ring. Their cover has its gasket attached.

In the figure above, you can see that the fuel pump does not need a cam locking ring. It has a metal cover that is tightened in a criss-cross pattern to secure a fuel pump and avoid fuel leakage.

On the other hand, in some vehicles, a cam locking ring is strategically tightened to secure the new fuel pump.

The tightening method of the cam locking ring can be different for each vehicle. So, make sure to follow the instructions in the owner’s manual.

Furthermore, make sure that you replace the old gasket on the fuel tank with a new one while changing the fuel pump.

How to check for fuel leaks?

You need to verify the fuel pressure at the fuel rail to detect any fuel leaks. For this, you need a fuel pressure test kit.

Each vehicle has recommended fuel pressure range. So, you should check your vehicle’s manual. You also have to verify that fuel is reaching the fuel rail. To learn more, you can read my guide on the symptoms of a bad fuel pressure regulator.

How to fix?

If the fuel lines are not tightened enough, they can cause fuel to leak out. Make sure to tighten the fuel lines properly when installing a new fuel pump. Make sure to lubricate the fuel hose that goes on the fuel pump and the fuel pump outlet with a small amount of petroleum jelly.

Moreover, fuel lines can become brittle over time, due to which they can crack and cause fuel leaks after changing the fuel pump. So, when you snap all fuel lines on, make sure that they don’t have any cracks. 

Lastly, make sure to properly tighten the fuel hoses with the clamps after changing the fuel pump.

6. Inconsistent Reading on Fuel Gauge

The fuel gauge sending unit is a small device that is located inside your fuel tank. This unit comes with a fuel pump assembly. Its primary function is to measure the amount of fuel in your tank and send that data to your dashboard. This allows you to see how much gas you have left and when you need to fill up.

When the fuel pump pressure sending unit is working correctly, your fuel gauge should reflect the correct amount of fuel in your tank. 

Most people confuse the fuel pump and the fuel gauge sending unit. The fuel gauge sending unit itself is part of a fuel pump assembly. It consists of a controller and a level float with a long arm. The fuel gauge sender which is spot-welded onto the side of the fuel pump assembly

On the other hand, a fuel pump is a small cylindrical component you will find inside the casing of the fuel pump assembly.

If you’re just replacing the fuel pump instead of the whole assembly, the chances are that while taking the old fuel pump assembly out of the fuel tank, the electrical mechanism connected to the fuel level float arm has been damaged.

The fuel pump assembly has to be taken out at a slight angle so that the level float easily clears the opening.

Moreover, while re-installing the fuel pump assembly, make sure that the arm of the fuel level float sits in the same direction as the float arm of the previous fuel pump assembly was mounted. If you accidentally bend the float lever while installing the fuel pump, it will cause inconsistent fuel gauge readings.

If you only replace the fuel pump, and not the whole assembly, including the sending unit, the fuel gauge sending unit can damage due to high heat if the fuel level becomes less than 25% of the capacity of the fuel tank.

Common Problems After Changing Fuel Pump: FAQs