How to Start a Car With a Bad Fuel Pump


Your car’s fuel pump is perhaps the most important part of its fuel delivery system. A fuel pump is needed to move fuel from the tank to your engine’s cylinders. When a fuel pump starts to go bad, it can significantly affect the drivability of your car.

In this article, we’ll be going over what exactly it means when your fuel pump stops working, the symptoms of a failing fuel pump that you should look out for, how to prolong your fuel pump’s life, and of course, how to start your car if you have a bad fuel pump.

Fuel Pump Overview

Fuel pumps are standard equipment for all modern cars that use internal combustion engines. In decades past, some cars didn’t have fuel pumps and instead used gravity feed fuel tanks, but this is no longer the case.

The type of fuel pump your car has depends on its fuel delivery system. In older carburetor cars, the fuel pump is usually driven mechanically by the engine and is located closer to the engine itself. In newer cars with fuel injection, fuel pumps are usually operated electrically and are located closer to the fuel tank or even inside the tank.

Modern fuel-injected cars may use two pumps in their fuel systems. The first pump is usually a larger, low-pressure one that moves the fuel outside the tank, and the second pump is a smaller, high-pressure one that sends the fuel to the injectors.

What Happens When Your Fuel Pump Goes Bad

As we’ve mentioned, the fuel pump in your car is needed to pump fuel from the tank to the engine. When your engine is running at speed, it needs a consistent supply of fuel in order to operate correctly. Being unable to receive the right amount of fuel can throw off the air/fuel ratio in the cylinders, resulting in poor engine performance.

If your fuel pump is failing, your engine may be getting too much or too little fuel, and in either case, this is not good for your car’s performance.

An engine that is receiving too little fuel (running lean) will be prone to misfiring and may stall at lower speeds. An engine that is receiving too much fuel (running rich) will run far less efficiently and emit far more pollutants than normal.

If the state of your fuel pump is really bad, however, your car will be totally unable to start or run, which is obviously not something you want to have happen to you.

Related: How Often Should The Fuel Filter Be Changed?

How To Start a Car With a Bad Fuel Pump

If your fuel pump is indeed going bad, it may be next to impossible to get your car started to begin with. However, there’s one thing you can try that might make a difference. 

If your fuel pump is incapable of generating enough pressure on its own to start the car, you might be able to compensate by applying some external pressure of your own. At the very least, this might be able to help you start and run your car for long enough to get to a repair shop.

As for how to provide your fuel with external pressure, you might have to do a little experimenting and see what works. One thing you could try, however, is connecting an air pump to your gas tank and running it until the tank itself becomes pressurized.

Other than this, if your fuel pump goes kaput, there’s really no feasible way to start your car in spite of this. Some sources state that keeping your engine hot can also make it easier to start your car when your fuel pump is dying, although there doesn’t seem to be much of a basis for these claims.

Symptoms of a Bad Fuel Pump

It is important to know that your fuel pump is actually bad, before proceeding to trying to start a car when the pump might not be at fault.

Fuel pumps are generally very reliable, and can last about 100,000 miles without needing replacement. Hence it is more likely to become bad on older cars. But rest assured that If your fuel pump is indeed on its last legs, you’ll receive plenty of warning before it fails entirely. A failing fuel pump has several different symptoms, so pay attention for the following signs that your fuel pump is going bad:

1. Engine Sputtering When Driving Fast

A engine that sputters when you’re moving at speed is one of the biggest signs of a bad fuel pump. As you know, your engine needs a steady supply of fuel to run correctly, particularly when the engine is turning over quickly. Sputtering happens when your pump can’t deliver the right amount of fuel at the right pressure to your cylinders.

2. Low Fuel Pressure

If you’re able to measure your car’s fuel pressure, this can be an accurate way to determine if your fuel pump is going bad. A faulty fuel pump won’t be able to supply your engine fuel at the right pressure, so low fuel pressure can be an indication of a bad fuel pump.

There are a few different ways you can check your car’s fuel pressure. The easiest way is to simply use a fuel pressure gauge. 

To use a fuel pressure gauge, you need to connect it to your injector rail. Most modern cars, and especially old ones, should have a testing point for fuel pressure on the injector rail in the form of a Schrader valve. 

After connecting your pressure gauge to the valve, turn the key to the “on” position (not the “start” position. If your fuel pump is working, it should come on and start sending fuel to the injectors. If the fuel is coming in with enough pressure, the fuel pressure gauge should indicate this.

3. Surging Engine

If your fuel pump is sending too little fuel to the cylinders, your engine will start sputtering. On the other hand, if your fuel pump is sending too much fuel to the cylinders, this can cause your engine to start surging unexpectedly. 

You’ll be able to tell if your engine is surging if your engine starts suddenly gaining revs even when you’re not actively pressing the gas pedal.

4. Poor Fuel Economy

An engine that is running too rich will end up wasting fuel, since more fuel is being sent to the engine than it can actually burn. This, of course, can happen if your fuel pump’s pressure is too high.

Pay attention to your car’s normal gas mileage, and take note if your mileage is starting to go way down for no apparent reason. The culprit could very well be a bad fuel pump.

5. Sluggish Acceleration

If your fuel pump can’t provide fuel to your engine at the right pressure or volume, this can result in a vehicle that struggles to accelerate normally.

If you happen to suspect that your fuel pump is on the fritz, try doing some hard acceleration on a road or another place where it’s safe to do so. A car with a bad fuel pump will accelerate a lot more weakly than it normally would.

Read: Why Does My Car Shake When I Accelerate?

6. Power Loss

You may also notice the signs of a bad fuel pump if you try to drive with one while the vehicle in under extra load, for example if you’re driving on a steep hill or pulling some heavy cargo.

Your engine needs more fuel in order to work harder in these situations, and if your fuel pump can’t supply this extra fuel, you’ll definitely notice it. 

7.Strange Noises

Fuel pumps do normally make noise, but if your pump is operating normally then you shouldn’t be able to hear the noise over the sound of your engine. A functioning fuel pump normally makes a low humming sound, which you might be able to hear if you put your ear close to your car’s fuel tank while it’s running.

A broken fuel pump, on the other hand, can be a lot noisier than normal. If you hear what sounds like a loud whining noise coming from the rear of your car while it’s running, this could be because you have a busted fuel pump. 

8. Hard/No Starting

If your fuel pump issues get really bad, you may find it a lot harder than normal to start your car. With a bad fuel pump, the engine may turn over several more times than normal before it is able to start.

If the fuel pump has failed completely, then the engine will be completely unable to start. The starter motor will keep the engine turning over, but it will fail to run otherwise. In this case, replacing the fuel pump is probably your only option.

How to Prolong Your Fuel Pump’s Life

It’s all well and good to know how to deal with a fuel pump after it goes bad, but learning how to take care of your fuel pump so that it doesn’t go bad to begin with is also incredibly useful to know.

Prolonging the life of your fuel pump mainly comes down to two things: your refueling habits, and the quality of fuel you put into your car. 

In terms of your refueling habits:

  • You can help preserve the life of your fuel pump by not waiting too long to refuel your car. If you can, try and make sure that your fuel tank is at least a quarter of the way full at all times.
  • This is because gas acts as a coolant for your fuel pump, and if there’s not enough gas to cool the pump, then the pump will obviously start to overheat. This can cause the pump to wear out more quickly.
  • The presence of extra fuel in the tank also helps with the longevity of the fuel pump by not requiring it to work as hard. If there is more fuel in the tank, there is also more internal pressure, which helps to move the fuel through the pump more easily. When fuel starts running low, the pump has to work harder to send the same amount of fuel through it.

Any dirt or debris that gets into your gas tank can damage the fuel pump if it gets sucked in. Debris tends to accumulate at the bottom of your gas tank, so the lower your fuel levels get, the more likely your fuel pump will be sucking in unwanted bits. 

You should also try to avoid refueling at run-down, poorly maintained gas stations, since they might be more likely to have impurities in their gas. If their supply of gas is contaminated with water, for example, this can cause your fuel pump and other parts of your fuel system to start corroding.

Read: Fuel Induction Service – What Is It and How Its Done?

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