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Give Your Car New Life After Fuel Pump Replacement

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The fuel pump is responsible for supplying the essential air pressure to the fuel in the engine to start it. The fuel pump usually lasts a couple of years or around 100,000 miles. After that, you need to replace the fuel pump for the smoother performance of your car engine. Replacing a fuel pump may seem easy, but you might face difficulty starting the car afterward. 

So, you must understand how to start a car after replacing the fuel pump. Usually, the car won’t start due to inaccurate fuel gauge reading, a faulty regulator of the fuel pump, incorrect fuel pump pressure, and other reasons. 

Hence, you must investigate the problem of the newly installed fuel pump and its connecting parts. Only then can you fix the fuel pump problem to start your car. And today, we will discuss everything about the newly installed fuel pump and ways to start your car safely. 

What Problems May Occur After Fuel Pump Replacement?

When replacing the fuel pump, you must be careful to start the car afterward. The fuel pump may need an accurate pressure gauge, air pressure, or faulty regulator. These problems can cause the engine to not receive enough fuel or stall after starting. 

Air in the Fuel Line: 

When you replace the fuel pump, sometimes air can get trapped in the fuel lines. It often happens because of negligence in taking proper measures to stop the air entrance. 

The trapped air will disrupt the fuel delivery system. As the fuel system has trapped air, fuel can’t go quickly to the engine. Also, the trapped air may get mixed with the fuel. All these will lead to difficulty starting the car or erratic engine performance.

To solve this problem, thoroughly check the fuel pump, pressure gauge, and wiring. Also, allow the car to adjust for some time, and then you may start it. 

Fuel Pressure Imbalance:

Sometimes, the fuel pump installation can be incorrect or become faulty. So it can result in inconsistent fuel pressure. The engine will only respond appropriately if the fuel pressure is consistent and accurate. 

Naturally, the engine will face starting issues, poor acceleration, and stalling. You must recheck the pump if you see the engine stalling or failing to accelerate after the fuel pump replacement. Also, you should examine the pressure to see if it is wrong or accurate. If the pressure reading is inaccurate, you should check the pressure gauge. 

Inaccurate pressure gauge and regulator:

After replacing the fuel pump, you need to finetune it with the fuel pump pressure gauge and regulator. The regulator is responsible for controlling the air pressure inside the fuel pump. Also, the pressure gauge takes the fuel pump pressure readings to allow the regulator to control it. 

The fuel pump pressure gauge takes accurate readings so that it will respond poorly. Also, with correct readings, it sends accurate signals to the regulator. So, it will either stop the fuel pump’s air intake or allow more air into the pump. 

In both cases, you will see that the fuel pump is not working correctly. In such cases, you need to check the pressure gauge and the regulator. The best thing is to check the fuel pump wiring and redo it, following the user manual. You should ask a professional to check and fix the fuel pump regulator and pressure gauge so that they perform consistently. 

Electrical Connectivity: 

During the fuel pump replacement, it is crucial to connect the pump with the connecting electrical wirings safely. However, at times, the electrical connections of the fuel pump may need to be properly reconnected. 

When it happens, your car’s engine control module may not receive the necessary signals. It occurs as the fuel pump sensor fails to receive the signal through the wiring. It will naturally affect the fuel injection process of the engine. 

So, either the engine will receive faulty fuel pressure readings or get inaccurate signals. In both cases, your car engine will not start. Even if it starts, you will find that the engine will stall and stop working within a few moments. 

As it happens, you must recheck the fuel pump’s electric wiring. You can fix the electronic connections following the user manual. Your car manual will clearly describe which plug and wire to connect which part of the fuel pump. 

Hence, you should have no difficulty reconnecting the electrical connections and sensors of the fuel pump accurately. 

Faulty Fuel Pump Relay: 

The fuel pump relay controls the fuel pump’s operation. It will control how much air should get into the fuel pump and how much pressure it generates for the engine fuel. Hence, when the relay malfunctions, your car may not start at all.

Check the relay carefully if your car engine doesn’t start, even after the fuel pump replacement. You must ensure that its wires are connected correctly and it delivers the right readings for the fuel pump. 

Fuel pump not working:

Finally, the fuel pump itself can be a problem. You may have installed it inappropriately. Or your fuel pump has misaligned connections. All these will stop the fuel pump from working, so your car engine will not receive enough fuel pressure. 

Naturally, your car engine will not start with inadequate fuel pressure. Therefore, you must check the fuel pump and see if it works correctly. 

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how to start car after replacing fuel pump

How to Start Car After Replacing Fuel Pump: Step-by-Step Guideline

Replacing the fuel pump of your car is an essential maintenance task. So, when you replace it, you shouldn’t haste in starting your vehicle. Instead, take time to check that the replacement is proper with the correct wiring and electrical connections. Only then may you consider starting your car. 

Step 1: Check the Fuel Level

You should park your car in a well-ventilated area. It needs to be away from open flames or sparks since, with inaccurate fuel pump pressure, the fuel may ignite unknowingly inside the engine. Also, you must engage the parking brake to stop the car from moving even with inaccurate acceleration. 

  • Then, check for the fuel inside the fuel tank.
  • Ensure that you have a sufficient amount of fuel in the tank.
  • A low fuel level would reduce the pump’s ability to draw fuel effectively.

Step 2: Prime the Fuel System

Once you are satisfied that the fuel tank has enough fuel and the regular fuel pump gauge is working properly, proceed to the next step. 

  • First, turn the ignition key to the “On” position. You need to do it without starting the engine.
  • Now, carefully listen for a distinct humming sound. 
  • The sound indicates that the fuel pump is priming the system. 
  • You will have to repeat this process a few times to ensure proper pump pressurization so that the engine receives appropriate pressure. 

Step 3: Cycle the Ignition

After priming the fuel pump, turn the key to the “Off” position. Then, keep it for a few seconds and return to the “On” position. It will prime the system further and allow the fuel to reach the engine.

Make sure, during the priming period, the car is idle. So, engage the brakes and stop the car from moving, or the engine may not receive the fuel. Also, as you turn on and off the engine, it helps the engine to warm up, which will facilitate easy ignition and starting. 

Step 4: Start the Engine

Once the fuel system is primed, turn the key to the “Start” position. If the engine cranks but doesn’t start immediately, don’t keep cranking excessively, as this could flood the engine. Instead, you should wait and then try starting the car again. 

In some cases, the engine might take a few attempts to start due to air trapped in the fuel lines. During this time, be patient. If the engine doesn’t start, you may need to repeat the priming process. Also, you should check for the fuel gauge regulator and start the engine. 

Step 5: Monitor Engine Performance

Once the engine starts after replacing the fuel pump, you should observe the engine’s performance. Also, check the dashboard indicators and listen for any unusual sounds. Did you notice any issues, such as:

  • Engine rough idling
  • Engine stalling
  • Poor acceleration

If so, it’s best to turn off the engine. Then, you must recheck the fuel pump installation. Take your car for a short test drive when the engine runs smoothly. It will help you know that the engine and fuel pump are working correctly. 


Your fuel pump replacement should be perfect. Nonetheless, in many cases, the fuel pump sensor, gauge, relay, and electrical connections will not synchronize. At this point, you will have difficulty starting your car. As it happens, follow our suggestions on how to start a car after replacing the fuel pump. 

The key is to prime the fuel pump with enough fuel and ensure proper connections. With it, your car will perform smoothly after you have replaced the fuel pump.

Frequently Asked Questions:

  • What to expect after replacing the fuel pump?

You may see the engine idling or stalling after you replace the engine. Also, the fuel pump gauge may show inaccurate readings and cause the fuel pump to stop working.

  • How do you prime a fuel pump after replacing it?

You need to fill the tank with enough fuel and then continuously turn on and off the engine repeatedly. It will allow you to properly prime the engine and fuel pump after the replacement.

  • Why do my cars have no gas after using a new fuel pump?

If the engine has no fuel after replacing the fuel pump, there may be inadequate pressure inside the tank. Ideally, the pressure gauge should show 45PSI to 60PSI reading. So, you must ensure that the fuel pump gauge is working properly.

When the fuel injector installation is completed, turn the ignition key to the “start” position. And do it continuously several times. Keep remembering you should place it on for a few seconds.

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