Bad Fuel Pump Symptoms

The average fuel pump is built to last 100,000 miles or more—which is why many car owners barely give it a second thought. However, if your fuel pump starts to malfunction, it could lead to major performance and road safety issues.

The fuel pump is vital to your car’s fuel system as it is responsible for delivering fuel from the gas tank to the engine at the right pressure. If the fuel pump fails, your car engine may not start or it could stall while you’re driving.

In this article, we’ll go over the major signs and causes of a failing fuel pump. We’ll also provide helpful tips on how to diagnose and replace a fuel pump that has gone bad.

There are several warning signs of a faulty fuel pump. Recognizing these symptoms early can help you avoid unexpected situations, such as getting stranded on the side of the road or experiencing road accidents.

The most common symptoms of a bad fuel pump are:

Erratic Engine Behavior

A sputtering or misfiring engine is one of the tell-tale signs of a fuel pump going bad. Other major red flags include the engine stalling or surging suddenly while driving and trouble starting your vehicle.

Another possible sign, although much less common, is an increase in your engine’s temperature due to fuel starvation. In rare cases, this can cause the engine to run lean, which might increase the risk of overheating.

Unexpected Power Losses

Sudden power losses while accelerating, driving uphill, or driving with heavy cargo could indicate a faulty fuel pump. This happens because the engine is likely not receiving enough fuel due to the failing part.

Strange Noises

A functioning fuel pump typically operates quietly. However, if you hear a loud, whining or humming sound coming from the gas tank, this could point to a bad fuel pump. That said, some faulty fuel pumps can fail without making a noticeable sound.

Decreased Fuel Efficiency

If you start to notice a sudden drop in fuel efficiency or find yourself needing to refill the tank more frequently, this may indicate a failing fuel pump. This is because it may no longer be delivering fuel efficiently to the engine.

Illuminated Check Engine Light

Problems with your vehicle, particularly in the instance of a failing part, will usually trigger the ‘Check Engine’ light. This is likely the case with a faulty fuel pump as well, especially if the engine control module detects issues with fuel delivery.

The most common causes of fuel pump failure are:

Contaminated Fuel

Fuel that contains contaminants (e.g. water, dirt, debris, and rust) can damage the fuel pump over time. These contaminants can increase friction, resulting in the premature wear of the fuel pump’s components. Contaminated fuel will also clog other critical components, like the strainer and filter, leading to further issues.

Gradual Wear and Tear

While fuel pumps are pretty sturdy components, they are still susceptible to wear and tear over time. Older vehicles or those with high mileage are also more prone to fuel pump issues simply due to the age and wear of the components.

Driving with Low Fuel

Frequently driving your vehicle with low fuel can cause the fuel pump to overheat. Aside from powering your vehicle, fuel acts as a coolant on the fuel pump. When the fuel level is too low, the pump isn’t being cooled enough, causing the fuel pump to overheat and wear out faster.

Want to know if a bad fuel pump is the source of all of your car performance problems? The best (and safest) way to diagnose a bad fuel pump is to take your car to a certified mechanic or dealership.

If you want to try the DIY route, consider testing using a fuel pressure gauge. One common issue in faulty fuel pumps is low fuel pressure. To perform this test, you’ll need a fuel pressure gauge, a screwdriver, and supporting tools (e.g. ratchets and sockets).

Follow these steps:

1. Park Safely: After parking your car, apply the parking brake and turn off the engine. Give your engine sufficient time to cool down.

2. Locate the Fuel Pressure Testing Port: Find the fuel pressure testing port, which is usually located on the fuel rail.

3. Prepare for Fuel Leakage: Place a rag underneath the testing port to catch any fuel that may leak when the pressure tester is installed.

4. Install the Pressure Tester: Attach the fuel pressure gauge to the testing port.

5. Start the Engine: Once the pressure tester is installed in the port, switch the engine on and record the pressure reading.

6. Consult the Manufacturer’s Manual: Check your manufacturer’s manual for the correct pressure specifications and any specific procedures. For example, some manuals will suggest checking the pressure with the engine running at a specific RPM.

7. Evaluate the Results: If the fuel pump fails to meet the required pressure specification, it is likely that the fuel pump is not supplying sufficient fuel to the engine.

The cost of fuel pump replacement parts will vary depending on whether you choose OEM or aftermarket. OEM fuel pumps generally cost between $200 to $1,000, while aftermarket fuel pumps generally cost between $50 to $400.

If you go with a professional mechanic, the average cost to replace a fuel pump (including parts and labor) will range between $400 to $1,600 or more. The cost to replace a fuel pump will vary depending on many factors, including the cost of labor in your area, your vehicle make and model, product price, and warranty coverage.

If you want to go the DIY route to replace your fuel pump, err on the side of caution by donning safety glasses and gloves. Work in a well-ventilated area, have cleanup materials ready to mop any spills and have a fire extinguisher within reach.

To replace your vehicle’s fuel pump yourself, follow these steps:

1. Relieve Fuel System Pressure: Before disconnecting any fuel lines, start by relieving the system pressure. To accomplish this, switch off the engine, then press the Schrader valve (located on the fuel rail) for a few seconds. Use a rag to capture any fuel spray that comes out as you relieve the pressure.
2. Remove the Fuel Tank (if necessary): Next, you’ll need to remove the fuel tank from the vehicle. The removal process varies depending on the car and will require raising the vehicle with a jack and supporting it securely. On some models, an access port may be under the rear seat or in the trunk area, making tank removal unnecessary.
3. Disconnect Wiring and Fuel Lines: Take note of the wiring and fuel connections before conducting the fuel pump replacement. Carefully remove all of the connections, making sure no damage occurs to the fittings.
4. Remove the Old Fuel Pump: Loosen the large lock ring or fastener holding the fuel pump in place (this can vary by vehicle). Once removed, carefully lift the old pump out of the tank or access port.
5. Install the New Fuel Pump: Place the new pump into the tank or access area. Reconnect all wiring and fuel lines as they were before removal and reassemble any parts removed during the process.
6. Test the System: To ensure that everything is working properly, perform a quick test. Turn the ignition without starting the engine to pressurize the system, then check for leaks. Once everything is secure, start the engine to verify proper pump function.

Will a bad fuel pump throw a code?

A bad fuel pump by itself won’t throw a diagnostic trouble code, but it can throw a code indirectly due to the problems it causes. If a vehicle has a failing fuel pump, it can experience misfires, fuel pressure issues, and problems with the other components of the fuel system—all of which can trigger various trouble codes.

How long can you drive with a bad fuel pump?

It’s usually possible to drive with a bad fuel pump, but there isn’t a specific length of time as this would depend on factors such as road conditions, your vehicle’s make and model, and the extent of your fuel pump’s deterioration. Doing this, however, isn’t recommended. It could lead to stalls, severe engine damage, and even fires. Drive your vehicle to the nearest mechanic as soon as possible.