How to Tell if Your Fuel Pump Seal is Bad

Fuel smell coming from your machine? Whining noises, difficulty starting, sputtering, stalling, or reduced performance? These could all be symptoms of a bad fuel pump seal.

Left unchecked, a faulty seal can lead to dangerous leaks and severe engine damage.

In this post, we’ll walk through how to diagnose the issue and determine if you need to replace your fuel pump seal.

Symptoms of a Bad Fuel Pump Seal

• Fuel smell: If you notice a strong fuel odor coming from your vehicle, particularly around the fuel tank area, it could indicate a leaking fuel pump seal allowing fuel vapors to escape.
• Whining noise from the fuel tank: A damaged fuel pump seal can cause a distinct whining or buzzing noise emanating from the fuel tank area when the engine runs.
• Difficulty starting the engine: A failing fuel pump seal can lead to a loss of fuel pressure, making it harder for the engine to start, especially when the engine is cold.
• Engine sputtering or hesitation: If the fuel pump seal is not maintaining proper pressure, the engine may sputter, hesitate, or experience rough running during acceleration or under load.
• Engine stalling: In more severe cases, a bad fuel pump seal can cause the engine to stall unexpectedly, particularly at low speeds or when idling.
• Reduced power and performance: As the fuel pump struggles to maintain adequate pressure due to a faulty seal, the engine may feel underpowered and sluggish.

Diagnosing a Bad Fuel Pump Seal

Check for fuel leaks

Carefully inspect the area around the fuel pump for any signs of gasoline or diesel fuel. Common leak points include the pump mounting flange, fuel line connections, and the pump body itself.

Listen for unusual noises

Listen closely for any whining, whirring, or buzzing sounds that seem to be coming from the fuel pump location, especially when the engine is running. These noises may be more noticeable during acceleration or when the fuel tank is low.

Check the fuel pump relay

Locate the relay, typically in the engine bay fuse box or under the dashboard. With the ignition on, listen for a clicking sound from the relay when the key is turned to the “on” position. If no click is heard, the relay may be defective, causing fuel pump issues unrelated to the seal.

Check fuel pressure

Use a fuel pressure gauge connected to the fuel rail to measure the pressure while the engine is running. Compare the readings to the manufacturer’s specifications. If the pressure is consistently below the recommended range, it suggests a leak in the system, possibly due to a failing seal.

Check the fuel pump’s electrical circuit

Check the voltage at the fuel pump connector using a multimeter. With the ignition on, the reading should be close to battery voltage (12-14 volts). If the voltage is low or absent, inspect the wiring harness and connections for damage or corrosion. Electrical problems can cause the pump to work intermittently or not at all, even if the seal is intact.

Inspect the fuel pump

If the previous diagnostic steps suggest a bad seal, the fuel pump may need to be removed and inspected. This process typically involves draining the fuel tank and accessing the pump from inside. Once removed, closely examine the pump for signs of leaks, cracks, or other damage. Pay special attention to the condition of the rubber seal and its mating surfaces.