How to Start a Car With a Bad Fuel Pump

By Jed Lehman •  Updated: 05/10/22 •  11 min read

If you are wondering how to start a car with a bad fuel pump, you are in the right place.

The fuel pump is responsible for transferring liquid from the gas tank to a vehicle’s fuel injection system or carburetor. While older vehicles have a carburetor, most modern vehicles have fuel injection systems. Nowadays, most fuel pumps are responsible for pumping gasoline to a car’s fuel injectors. The fuel injectors then provide the engine with fuel to create combustion. With a bad fuel pump, combustion is challenging to achieve and vehicles will have trouble starting. 

A malfunctioning fuel pump also reduces the effectiveness of an engine and can make it hard to reach the mechanic without a tow truck. Unfortunately, tow trucks cost money, so getting a car started and running with a bad fuel pump can save you some money.

We’re going to take you through everything you need to know about fuel pumps. We’ll talk about some of the reasons they fail, how to maintain them, and how to start a car with a bad fuel pump.

Read on to learn more.

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What Is a Fuel Pump? 

How Does a Fuel Pump Work?

Fuel pumps work in various ways depending on the type of vehicle. Typically, the fuel pump combines mechanical force with pressure.

While many engines operate the fuel pump, some vehicles also have fuel pumps that combine electrical energy with pressure.

Moreover, some vehicles can use a combination of both mechanical and electrical energy. Still, fuel pressure needs to remain consistent because too much or too little pressure creates imperfect combustion.

The fuel pump itself resembles a small jar. A jar-like design is important because the fuel pump has several components that function together.

what is a fuel pump

First and foremost, the pump has a vacuum-like system that draws fuel from the fuel tank. Once fuel from the tank fills the pump the fuel is filtered through mesh filters to prevent residue from the fuel tank from mixing with the fuel.

Then, the fuel enters a metering pump. The metering pump spins, mixes, pushes, and pulls the fuel to add pressure.

Finally, fuel from the fuel pump is sent to the engine through the fuel line. When the fuel reaches the engine many nozzles spray fuel into the combustion chambers.

The fuel that’s sprayed into the combustion chambers is also mixed with air to achieve the proper fuel-to-air ratio that’s required for combustion. In summary, this is how most modern fuel pump systems function.

Where Is The Fuel Pump Located? 

The location of the fuel pump varies depending on the vehicle. Many vehicles have a fuel pump that’s located inside or near the fuel tank.

On the other hand, some vehicles have fuel pumps that are closer to the engine. It’s also possible for vehicles with a fuel injection system to have two fuel pumps. In these situations, one fuel pump has more pressure but less fuel, while the second pump has less pressure but less fuel.

These systems are commonly found in high-performance vehicles that have larger engines (like a v8).

What Causes a Fuel Pump to Fail?

Fuel pumps can fail for numerous reasons. Some of the common factors that cause a fuel pump to fail are listed below:

The fuel pump is responsible for sending pressurized fuel to the engine. If the fuel pump is operating with little fuel it can cause the fuel pump motor to become damaged.

Bad Fuel Pump Symptoms 

Cars break and don’t run properly for many reasons. Identifying the cause of an engine issue is crucial if you want your vehicle to run normally. If you’re unsure if a fuel pump is a problem, we have several symptoms that are caused by a bad fuel pump. Keep in mind that some symptoms vary based on the vehicle.

Problems Starting

One of the most common symptoms of a bad fuel pump is the engine not starting. Because the fuel pump transfers fuel from the fuel tank to the engine, a bad fuel pump won’t move the necessary fuel to start a vehicle. If a fuel pump is the cause of an engine not starting the engine will crank but won’t fully turn over. A bad fuel pump can also prevent a car from running once it’s started. For example, the vehicle might start and then stall. 

Problems with an engine starting can be caused by many factors, so we recommend starting with the normal causes like a dead battery or faulty starter; you should also check your fuses. Then, you can move on to checking the fuel pump and other more complex components.

Engine Stalling 

The engine stalling can also be a symptom of a bad fuel pump. While engines can stall for any number of reasons, an engine that stalls because of a bad fuel pump is noticeable. An engine that stalls because of the fuel pump will also have a higher temperature reading. You’ll also notice issues with oil temperature, fuel pressure, and other indicators.

Engine Sputtering and Surging  

The fuel pump delivers a constant stream of fuel to the engine for combustion. When fuel doesn’t reach the motor consistently many problems can occur. The engine can surge, which means it will have higher or lower outputs of power randomly. An engine with a bad fuel pump will also experience sputtering. Sputtering at highway speeds and then running normally again is one of the most common signs of a bad fuel pump because it’s an issue that’s unique to the fuel pump.

Dangers of Having a Bad Fuel Pump 

Symptoms of a bad fuel pump are problematic, sure, but running a vehicle with a bad fuel pump leads to several consequences. A bad fuel pump can damage a vehicle’s engine, fuel delivery system, fuel injectors, and other essential components. Below are the problems caused by running a vehicle that has a bad fuel pump:

Based on the potential problems that are caused by running a car with a bad fuel pump, you should avoid doing so. We only recommend running an engine with a bad fuel pump if you’re going to a mechanic.

How to Start a Car With a Bad Fuel Pump 

We advise against starting a car with a bad fuel pump. If your vehicle is not starting, it’s not always a good idea to force it to start. However, starting a car with a bad fuel pump can help you reach a repair shop without paying for a tow truck. In these situations, it’s acceptable and even worthwhile to start a car with a bad fuel pump. Below are the steps to start a car with a bad fuel pump.

1. Use a Fuel Pressure Gauge

Before attempting to start a car with a bad fuel pump you need to measure the car’s fuel pressure with a fuel pressure gauge. A fuel pressure gauge is an inexpensive tool that shows you how much pressure there is within the engine. Low-pressure readings mean that the fuel pump is bad and needs to be repaired or replaced. We always recommend starting with a fuel pressure gauge because it gives you definitive proof that it’s a fuel pump problem.

2. Focus on External Pressure 

To begin starting a car with a bad fuel pump you need to start with pressure. The fuel pump delivers pressurized fuel to the engine, so you need to replicate this mechanism without the fuel pump. To do so, you have to create pressure in other ways. Our favorite way to get external pressure is to use something like a mattress pump.

Here’s how you can use a mattress pump to start a car with a bad fuel pump:

  1. Remove the screw from the fuel filter with a flathead screwdriver.
  2. place the pump into the fuel tank and connect it to the fuel line.
  3. Give the mattress pump a few good pumps (3-6 should do it).
  4. Remove the pump from the fuel line and connect the fuel line back to the fuel filter. Do this quickly to prevent fuel from squirting everywhere. 
  5. Fasten the screw to the fuel filter and attempt to start the vehicle.

These steps should give you enough fuel to start the engine. 

3. Balancing Engine Heat  

Once you’ve started a vehicle that has a bad fuel pump, it’s time to balance the engine’s heat. Unfortunately, this is where things get tricky. Depending on the type of damage a fuel pump has sustained, a bad fuel pump can cause an engine to overheat. If an engine is overheating, you’ll need to open the heat vents and blow hot air out of the vents as you drive to a repair shop. Keep an eye on the temperature gauge and turn off the vehicle if it reaches critical temperature levels.

The reason that balancing engine heat is tricky with a bad fuel pump is because a warm engine is easier to run fuel through. Having a warm engine makes it easier for a bad fuel pump to move fuel and can even keep an engine with a bad fuel pump running. If overheating is not the problem, make sure the engine does not become too cold. An engine that’s too cold will have trouble moving fuel through the fuel lines and fuel injectors.

Fuel Pump Maintenance 

Maintaining a fuel pump can prevent the fuel pump from failing. Plus, maintaining a fuel pump is easier than replacing the fuel pump or paying for a fuel pump to be replaced by a professional. We’re going to take you through some simple ways to maintain a fuel pump. Below are some fuel pump maintenance tips:

Fuel pump maintenance is more about good habits than getting your hands dirty. As long as you keep fuel in the tank and avoid using bad fuel you shouldn’t have any issues with the fuel pump.

Keep That Fuel Pumping!  

A bad fuel pump will prevent your vehicle from starting. Even if you manage to start a car with a bad fuel pump its performance will be compromised. Given these conditions, we recommend against starting a car with a bad fuel pump unless you’re trying to drive up the road to a repair shop. 

If the repair shop is close and you’re confident that you can make it before the engine sustains damage, our steps to start a car with a bad fuel pump will help you get there. Remember, be safe and only run a car with broken components if it’s necessary.

Jed Lehman

Jed Lehman is a born gearhead who has been working on cars since he could crawl. He inherited his love for auto from his grandfather who owned a maintenance shop in Carlsbad, California. Jed is the driver behind Gearshift, and started this site to provide straightforward, helpful automobile information. From maintenance tips to product reviews, you can find it all here.