7 Symptoms of a Bad Fuel Pump
The fuel pump is a vital part of an internal combustion engine. It is responsible for pumping fuel from the gas tank through the fuel lines into the combustion chambers, where a mixture of fuel and air must be present.
A fuel pump is a simple electromechanical device that moves fuel from one place to another. In most cars, fuel is pumped from the gas station to the gas tank in the rear of the car, where it is needed by the engine in the front of the car. When you start your car, the fuel pump pressurizes the fuel system and pumps fuel to the front of the vehicle. The pump is usually located in the fuel tank and is submerged in the fuel. The surrounding fuel cools the fuel pump during operation. Some vehicles have another pump along the fuel line or in the engine bay to further pressurize the fuel. For example, direct injection vehicles require a second high-pressure fuel pump to bring the fuel pressure from 60-80 psi to about 2,000 psi or more.
As long as the fuel pressure regulator is working, there will be no excess pressure in the fuel lines. Fuel is forced into the injectors and passes through a fuel filter to remove impurities before being sprayed into the cylinders in precise amounts.
Older vehicles may use a mechanical pump that uses a piston or diaphragm to move fuel to the carburetor, which then creates suction to move the fuel to the injectors. Newer vehicles with electronic fuel injection have high pressure requirements that can only be met with an electric pump.
Many of these symptoms can also occur when other components in the fuel system are defective. You may need to perform tests or diagnostics to determine which fuel system components need to be replaced.
1) Vehicle is hard to start (Car starting problems)
If your car won’t start when you leave the ignition on, or if it starts but stalls immediately, make sure you hear the fuel pump working when you first turn the key to the “on” position. Most fuel pumps make a whirring noise as the pump fills the fuel lines when you start the car. In some vehicles, the fuel pump primes when you unlock the car or open the driver’s door. This process varies by manufacturer, but is more common in European cars.
2) Stalling (especially under load) (engine stalling)
If your engine suddenly stalls while driving, this could be a sign of a faulty fuel pump.
If your car runs fine under normal conditions but stalls when under load (such as when accelerating or transporting heavy items), the problem may be due to the fuel pump failing to withstand the load.
3) Stuttering, rough running
If your engine is coughing or generally running rough at idle or low speeds, this could be an indication of a problem with the fuel pump. These can be caused by engine misfires due to unbalanced cylinder function. 4) Poor performance (slow acceleration)
Cars with defective fuel pumps often accelerate slower than normal when entering the highway. The pump cannot provide enough power to the engine, causing problems for the car. Driving uphill only makes this problem worse.
5) Engine jerking
If you are driving your car at a steady speed and suddenly the engine revs up and accelerates (even though you are not pressing hard on the accelerator), you may have a problem with the fuel pump. If this happens, be very careful to keep a good distance away from the car in front of you on your way to the repair shop so that you do not accidentally hit it.
6) Check Engine Light
Newer cars have complex sensor systems that should detect any fuel pump problems before other, more dangerous symptoms appear. Insufficient fuel pressure or flow through the injectors will be detected by the computer and will turn on the check engine light. An engine misfire should also raise a warning.
If the check engine light comes on, it’s best to have the car scanned to fix the problem. Take your car to a repair shop or auto parts store and have them read the codes with an OBD-II diagnostic tool. This will tell you what problem caused the warning so you or a mechanic can continue troubleshooting.
7) High-pitched whining (V-belt squealing)
If you hear a loud “whooshing” noise coming from the back of your car where the fuel tank is, check your fuel pump. It should usually make a quiet hum that the driver can’t hear while driving.
To perform a very simple fuel pump check, turn your car’s ignition to the “on” position while the fuel door and gas cap are open, and actually listen at the tank to see if the fuel pump is working properly. If you don’t hear anything, the pump may have failed.
Can a faulty fuel pump cause a rough idle? Yes, a faulty fuel pump can cause rough idling. If the engine has an irregular fuel supply, it may have trouble maintaining a smooth idle. An improper air-fuel mixture can also cause rough or turbulent idling.
What Causes a Fuel Pump to Fail (Fuel Pump Failure)
Like any other component, a fuel pump can fail due to wear and tear, but there are other reasons for fuel pump failure as well. Using low-quality fuel, running on diesel in a gasoline vehicle (or vice versa), or using too high a percentage of ethanol fuel in a vehicle not designed for ethanol are all causes of premature fuel pump failure. Driving with too little fuel in the gas tank can cause problems. It is important to drive with at least 25% fuel in the tank to prevent sediment from building up at the bottom of the tank.
What happens if the fuel pump fails while I’m driving?
If the fuel pump fails while I’m driving, the vehicle will stall and coast. If the fuel pump fails completely, you won’t be able to start the car. The vehicle will be unable to run and will need to be towed.
How to start a car with a broken fuel pump
Even if the fuel pump only fails intermittently, there may be a way to get the vehicle back home.
Find out what is causing the fuel pump to fail. Can you kill a car by shaking a part of the wiring harness? Could it be a bad relay connection?
Could the fuel pump suddenly fail?
Fuel pumps often give you warning before they fail, but sometimes they can fail suddenly. To avoid this situation, keep an eye on how your car feels and sounds.
Unless the fuel pump is to blame
1) Bad or clogged injectors (fuel injectors)
These are the final stop before the fuel enters the cylinders. This is where the magic happens, so an injector restricting the flow of fuel will certainly cause some problems.
2) Bad fuse or relay (fuse box)
Fuses and relays are easy to check and cheap to replace. This is often a good first step when troubleshooting at home.
3) Poor Electrical Connection (Symptoms of a Bad Ground Strap)
Modern systems rely on many sensors and connections to relay information. Short circuits and faulty grounds can cause many strange problems, especially intermittent problems.
4) Clogged Fuel Filter (Faulty Fuel Filter)
A clogged filter can restrict fuel, just as a clogged fuel injector can mean the cylinders don’t get the fuel they need.
5) Running Out of Gas
Never overlook the simple things. If you have a problem with your fuel gauge, you may be running low on fuel without realizing it.
