Mechanic Tips

Dealing with Fuel Pump Issues: Diagnosis and Replacement

A properly functioning fuel pump is essential for keeping your car running smoothly. However, fuel pumps can develop issues over time that lead to performance problems. In this article, we’ll explore common fuel pump problems, how to diagnose them, and when it’s time for replacement.

What Does the Fuel Pump Do?

The fuel pump delivers petrol from the fuel tank to the engine. It works by creating pressure to push fuel through the fuel lines and fuel filter before arriving at the injectors. Some key roles of the fuel pump include:

  • Drawing fuel from the tank and moving it forward into the fuel lines
  • Maintaining proper fuel pressure for effective fuel injection and atomisation
  • Pushing fuel through the filter to remove debris before it reaches injectors
  • Delivering the right fuel volume for optimal combustion

Any issues with fuel pump operation can lead to performance problems, so it’s important to address symptoms promptly.

Common Fuel Pump Issues

There are several problems that can affect the fuel pump:

Low or Inconsistent Fuel Pressure

The fuel pump must maintain a consistent pressure, usually between 35-85 psi depending on the vehicle. If pressure is too low, insufficient fuel will reach the engine leading to symptoms like hesitation, stalling, or no start. A faulty pressure regulator can also cause fluctuations in fuel pressure.

Fuel Pump Failure

Over time, internal components in the fuel pump can eventually fail. For instance, the pump motor may stop working entirely leading to a no start condition. Fuel pump failure is more likely in older vehicles.

Dirty Fuel Pump

Debris and sediment from the fuel tank can clog components inside the fuel pump. This restricts fuel flow, reducing pressure and volume output. Fuel filters help catch some debris but don’t catch everything.

Faulty Electrical Connection

Like any electrically powered component, the fuel pump relies on good wiring and connections to operate. Corroded contacts or faulty power or ground connections can cause an intermittent or permanent failure.

Diagnosing Fuel Pump Issues

Some common symptoms that indicate a potential fuel pump problem include:

  • Difficult starting or engine cranks but does not start
  • Engine stalling or misfiring
  • Lack of power under acceleration
  • Check engine light illuminating
  • Increased emissions or fuel smell

If you suspect a problem with the fuel pump, there are a few checks that can help diagnose the specific issue:

Pressure Test

Using a fuel pressure gauge to check fuel pressure directly is the most definitive test. Low or erratic pressure indicates a fuel delivery problem. You’ll need to locate the Schrader valve on the fuel rail to connect the gauge.

Listen for Fuel Pump Prime

Turn the key to ON and listen near the fuel tank. You should hear a whirring noise as the pump runs for a few seconds to prime the system. No noise may indicate pump failure.

Check Voltage at the Pump

Use a multimeter to check for power at the pump connector. If voltage is present, the electrical circuit is likely fine and the pump itself may be bad. No voltage indicates an electrical issue.

Visual Inspection

Check all fuel lines and connections for leaks, damage, or corrosion. The fuel filter may also be clogged with debris. Replacing fuel lines or the filter can sometimes resolve pressure issues.

By systematically testing and inspecting the fuel delivery system, you can zero in on what exactly is causing the pump to underperform. Replacement may be needed but diagnostics help identify any underlying electrical or filter issues first.

When to Replace a Fuel Pump

Here are some signs that indicate replacing the fuel pump completely may be the best solution:

  • Pump is completely inoperable and does not prime or run at all
  • Pressure readings are too low and filter/lines are okay
  • Pump is very noisy or whining
  • You’ve cleaned the pump and replaced the filter but issues persist
  • The vehicle has over 150,000 km on the original pump

While a faulty fuel pump relay or electrical issue can cause similar symptoms, if you’ve traced the problem to the pump itself then replacement is required. Intermittent issues also hint at a pump that is slowly failing.

Replacing the fuel pump is recommended about every 160,000 km, even if not exhibiting obvious symptoms yet. Worn pumps diminish performance over time.

Fuel Pump Replacement Tips

Replacing a fuel pump requires working with petrol and dealing with fuel lines under pressure. Use caution and follow some general tips:

  • Relieve fuel pressure before disconnecting any lines
  • Have an approved fuel container ready to catch any fuel leaks
  • Disconnect the negative battery cable before starting
  • Always replace the fuel filter when replacing the pump
  • Follow torque specs for any fuel line fittings
  • Prime the system several times to build up fuel pressure after installing
  • Check for leaks and recheck pressure at the fuel rail

While not incredibly complex, fuel pump replacement is an advanced DIY project. Having a professional mechanic do the work may be the best option for many. Proper disposal of the old petrol is also important.

When it comes to fuel pump issues, early diagnosis followed by a timely pump replacement when needed will keep your car running optimally. Pay attention to symptoms and be proactive with fuel system maintenance. Contact our expert mechanics at SNC Automotive in Brendale for quality fuel pump replacement services.

Frequently Asked Questions

What are the most common signs of a bad fuel pump?

Difficulty starting, stalling, lack of power, check engine light, and decreased fuel efficiency are some of the most common signs of a bad fuel pump. Fuel pumps may produce a loud whining noise as they start to fail.

Does a fuel pump normally run all the time?

No, a fuel pump usually only runs for a few seconds when the ignition is first turned on to prime the fuel system. Once started, it only runs intermittently to maintain fuel pressure. Continuous pumping may indicate a problem.

Can I drive with a bad fuel pump?

It’s generally not recommended to drive with a confirmed bad fuel pump. You may be able to limp the car to the shop if symptoms are mild, but complete failure at speed can cause the car to stall, creating a potentially dangerous situation.

How often should fuel pumps be replaced?

Most fuel pumps are designed to last around 160,000 km. Preventative replacement around this mileage, before major issues occur, helps avoid being stranded with a failed pump. Higher mileage vehicles may need pumps replaced more frequently.

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