Fuel Pump Secondary Circuit Intermittent

Possible causes

• CommonFailed fuel pump relay
• CommonBlown fuse on the fuel pump circuit
• CommonCorroded connector at the fuel pump or in the boot floor
• CommonFailed fuel pump
• PossibleDamaged wiring under the vehicle
• PossibleCorroded earth at the pump
• RareFailed control module driver

What you might notice

• Engine will not start
• Cutting out while driving
• Loss of power under load
• No fuel pump noise when the ignition is switched on
• Check engine light on

What to check, in order

1. Note whether it happens when hot. A pump that cuts out after twenty minutes and works again once cool is a failing pump; one that cuts out over bumps is a connection.
2. Wiggle-test the connector at the pump - on most cars it is reachable under the rear seat or through a boot floor panel.
3. Listen for the pump. Switch the ignition on without cranking and listen at the fuel tank - a working pump runs for a second or two. Silence is a clear finding and costs nothing to check.
4. Check the fuse and swap the relay with an identical one from elsewhere in the box.
5. Check for battery voltage at the pump connector while the pump should be running.
6. Check the pump earth connection - a corroded earth produces the same symptoms as a failed pump.
7. Inspect the wiring under the vehicle for corrosion and impact damage.