How to Diagnose and Fix a Bad Fuel Pump

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Debunking internet hacks about starting a car with a bad fuel pump

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Can you start a car with a bad fuel pump?

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What is the fuel pump?

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Signs the Fuel Pump is Bad

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Diagnosing a Bad Fuel Pump

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Expert Interview

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Tips

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Warnings

If your car won't start because of a faulty fuel pump, we're here to help. While you'll definitely need to replace the pump soon, there are some things you can try to get your vehicle running so you can drive it to an auto shop. In this article, we’ll explain how your fuel pump works, how you can get your vehicle started, and how to know if your fuel pump is bad in the first place.

Things You Should Know

If your fuel pump is bad, you probably can't drive your car. If it won't start, have it towed to a mechanic shop and get a new fuel pump installed.
Try to start the vehicle after waiting for the engine to cool off for 8 hours. This may be enough time for the fuel lines to even out and the pump to reset.
If you can get it started, drive your vehicle to a mechanic shop ASAP. Continually driving with a bad fuel pump may damage your engine or start a fire.
Avoid using tricks or hacks to temporarily start an engine with a bad fuel pump. They're dangerous and unlikely to work.

Section 1 of 4:

Can you start a car with a bad fuel pump?

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You probably can't start a car with a bad fuel pump. Your fuel pump is responsible for giving your engine fuel to ignite, and if it’s not functioning properly, your car won't start. Even if it does, your engine may spark with nothing to ignite. This is a fire risk, and you could potentially damage your engine or make the issue worse if you keep trying to start the car. If your fuel pump is bad, get the vehicle towed to a mechanic shop.^{[1]XResearch source}
- There are all kinds of hacks on the internet involving spraying the engine with carburetor cleaner or building a DIY fuel pump with a phone charger, but all of these fixes are insanely risky. You may hurt yourself, start a fire, or destroy your engine, so don't try them.
- There’s a hack out there involving an air mattress pump and the fuel line. This is highly likely to start a fire, since it’s basically impossible to do this without spraying fuel in your engine bay.^{[2]XResearch source}
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If your car just died, try waiting 8 hours before starting it and driving to a shop. If you’re cranking the car repeatedly or the engine is running but sputtering, stop. Wait for the engine to completely cool off. This may give your fuel lines time to completely equalize, and your vehicle’s computer system will have time to reset. If you’re lucky, your car will start and you can get it to the mechanic.^{[3]XResearch source}
- If your fuel pump is bad, you’re on a race against the clock. Your vehicle is going to start overheating soon so drive slow, don’t overaccelerate unnecessarily, and don’t take any detours.
- Bring a fire extinguisher with you on this trip. In the rare chance your engine catches fire, you’ll be able to put it out quickly.

Section 2 of 4:

What is the fuel pump?

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The fuel pump sends gas from the tank to your engine. How does your vehicle get the perfect amount of gasoline it needs to keep the engine running at a certain speed? The fuel pump! Inside your fuel tank, there’s a sensor that tells your pump how much gas is left in the tank. The pump draws that gas out and then feeds it into your engine where it combusts.^{[4]XResearch source}
- Without a functioning fuel pump, your engine won’t get the gas it needs to run smoothly. This can range from irritating (if the gas/air mixture is slightly off) to outright dangerous (if there’s not enough gas and the engine runs dry).
- While you can replace a fuel pump on your own if you’re an experienced gearhead, you’re better off paying a mechanic to repair or replace your fuel pump.

Section 3 of 4:

Signs the Fuel Pump is Bad

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High temperatures If your temperature gauge keeps rising the longer you drive, your fuel gauge might be going bad. The engine isn’t getting enough fuel to combust, so all of that excess heat from the spark has to go somewhere. This will cause the temperature to slowly rise the longer you run your car.^{[5]XResearch source}
- Fuel system issues are the number one cause of vehicle fires, so don’t keep driving for an extended period of time if you think the fuel pump is failing.^{[6]XTrustworthy SourceNational Fire Protection AssociationNonprofit organization devoted to eliminating death, injury, property and economic loss due to fire, electrical and related hazards.Go to source}
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Engine doesn’t start correctly If you need to crank the engine multiple times before the car starts, it’s a signal that the fuel pump isn’t directing enough gas into your system to start the engine right away. If the pump is completely dead, you may not be able to start the car at all.^{[7]XResearch source}
- If you jump the battery and the car still won’t start, it’s a sign that either the starter or the fuel pump is bad.
Does it feel like you have to press the pedal to the medal to get the car to accelerate even a little bit? That’s a sign your fuel pump is dying. The fuel pump is struggling to inject enough fuel to match the acceleration, so the engine may kick, accelerate slowly, or struggle to get up to speed.^{[8]XResearch source}
If it feels like there’s a delay between your pedal and the speed of your vehicle or your car seems to kick and jump when you’re driving, it might be an indicator your fuel pump isn’t providing a consistent amount of fuel.^{[9]XResearch source}
It may become hard to control a vehicle with a bad fuel pump. You’re used to driving with a consistent amount of fuel, but a bad fuel pump can impact your spark plugs, throttle sensors, or acceleration cables, all of which can make your steering wheel unwieldy or jerky.^{[10]XResearch source}
On most vehicles, the fuel pump is inside the fuel tank. The fuel lines run under (or next to) your driver’s seat. If the pump isn’t sending enough fuel, you may hear whizzing or whining noises coming from underneath or nearby your seat as your fuel pump struggles to deliver fuel.^{[11]XResearch source}
You’re not going to get the typical fuel mileage out of a tank that you’re used to if you’ve got a bad fuel pump. The fuel pump isn’t sending the correct amount of fuel, so you won’t get the efficient fuel consumption you’re used to.^{[12]XResearch source}

Section 4 of 4:

Diagnosing a Bad Fuel Pump

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Use a pressure gauge to confirm the fuel pressure is low. Pop your hood and find the open air valve on top of your engine (or fuel line).^{[13]XResearch source} Insert a pressure gauge designed for cars and tighten the attachment nut. Then, crank the engine. If the pressure gauge doesn’t move, your fuel pump is bad.^{[14]XResearch source}
- If the fuel pump is working, the pressure gauge will sit at 4-60 psi depending on the type of carburetor or fuel injection you have.
If your fuel pump is bad, your check engine light is probably on. If it is, insert an OBD-II scanner into the OBD port underneath your steering wheel. Run the scanner and then read the codes to see what the problem is. If your fuel pump is bad, the OBD-II scanner should say as much.^{[15]XResearch source}

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Tips

Change your fuel pump every 40,000–50,000 miles (64,000–80,000 km) to prevent the pump from failing.
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Warnings

Don’t wait for the gas tank to completely empty out before fueling up. This is a quick way to damage your car’s fuel pump and wear it down.^{[16]XResearch source}
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