Diagnose and Fix a Bad Fuel Pump. A failing fuel pump can prevent your car from starting or running efficiently. Here’s how to identify the symptoms, confirm the diagnosis, and fix the problem.
A Fuel pump is a component used in many liquid-fuelled engines (such as petrol/gasoline or diesel engines) to transfer the fuel from the fuel tank to the device where it is mixed with the intake air (such as the carburetor or fuel injector).
Carbureted engines often use low-pressure mechanical pumps that are mounted on the engine. Fuel injected engines use either electric fuel pumps mounted inside the fuel tank (for lower pressure manifold injection systems) or high-pressure mechanical pumps mounted on the engine (for high-pressure direct injection systems).
Some engines do not use any fuel pump at all. A low-pressure fuel supply used by a carbureted engine can be achieved through a gravity feed system, i.e. by simply mounting the tank higher than the carburetor. This method is commonly used in carbureted motorcycles, where the tank is usually directly above the engine.
Things You Should Know
- A faulty fuel pump often prevents the engine from starting or running smoothly.
- If your car won’t start, avoid relying on internet hacks, as they can be dangerous and may cause further damage.
- If your vehicle starts after cooling for 8 hours, drive it carefully to a mechanic and avoid overacceleration.
What is a Fuel Pump?
The fuel pump delivers gasoline from the fuel tank to the engine. Without it, your car’s engine cannot receive the gas it needs to combust and run efficiently.
Signs of a Bad Fuel Pump
- High Temperatures:
- The engine overheats as the fuel pump fails to provide sufficient gas for combustion.
- Warning: Prolonged driving with a failing pump increases the risk of a vehicle fire.
- Difficulty Starting the Engine:
- Repeated cranking may be necessary, or the engine may not start at all.
- Acceleration Issues:
- Sluggish acceleration, delayed pedal response, or struggling to reach speed.
- Surging or Jerking While Driving:
- Irregular fuel delivery causes inconsistent vehicle performance.
- Steering Problems:
- Erratic fuel supply can disrupt throttle sensors and make steering jerky or hard to control.
- Unusual Noises:
- Whizzing or whining sounds from under the driver’s seat, where fuel lines are located.
- Poor Fuel Economy:
- Irregular fuel delivery reduces efficiency, causing lower mileage per gallon.
Diagnosing a Bad Fuel Pump
- Check Fuel Pressure:
- Use a pressure gauge on the fuel line to measure fuel pressure.
- Normal Pressure: 4-60 psi, depending on the system.
- Low/No Pressure: Indicates a bad fuel pump.
- Run an OBD-II Scan:
- Plug the scanner into the OBD port under the steering wheel.
- Check for error codes related to fuel delivery or pump issues.
What to Do If Your Car Won’t Start
- Cool Down the Engine:
- Let the vehicle sit for 8 hours to allow fuel lines to stabilize.
- Attempt to start the car and, if successful, drive directly to a mechanic.
- Bring Safety Equipment:
- Carry a fire extinguisher in case of engine overheating or fire.
Repair Options
- Professional Replacement:
- Most reliable and safest option.
- Cost: $400-$1,200 depending on vehicle make and model.
- DIY Replacement (Experienced Mechanics Only):
- Remove the fuel tank to access the pump.
- Replace the faulty pump with a new one, ensuring proper seals and connections.
- Test the system by starting the car and monitoring pressure and performance.
Tips
- Avoid driving with a bad fuel pump: This can cause severe engine damage or fire hazards.
- Regular Maintenance: Ensure fuel filters and lines are in good condition to avoid premature pump failure.
By diagnosing and addressing a bad fuel pump promptly, you can save yourself from costly repairs and ensure your vehicle remains safe and reliable.
