Parts for your 2004 Subaru Impreza-Fuel pump

2004 Subaru Impreza fuel pump — purpose, care, and when to replace

Yes, a fuel pump is definitely used on the 2004 Subaru Impreza. Technical documentation including the 2004MY Subaru Factory Service Manual, the Subaru parts catalogue for GD/GG Impreza, and common workshop guides (e.g., Haynes) all specify an in-tank electric fuel pump module for both non-turbo and turbo variants. The unit sits under the rear seat base, mounted in the fuel tank, and supplies high-pressure petrol to the injectors for the car’s electronic fuel injection system.

What does it do? The pump draws fuel through a strainer (sock), pressurises it, and feeds the rail at the pressure specified by Subaru for the particular engine. Depending on market and engine, the pressure regulator may be on the rail or integrated with the in-tank module, but the pump’s job is the same: keep a steady, reliable flow so the ECU can meter fuel precisely. Without a healthy pump, the Impreza will struggle with starting, stumble under load, or lose power on hills and overtakes.

While the pump isn’t a routine “replace by kilometres” item, it does benefit from sensible care: keep a quarter tank or more to avoid heat and aeration, replace the strainer and tank seal (O-ring) any time the module is out, and stick with quality petrol. E10 is generally fine in AU/NZ for this generation, but high-ethanol blends can shorten pump life unless a compatible pump is fitted.

• Common signs it’s on the way out: hard starting, a loud whine from the tank, hesitation at motorway speeds, misfire under load, or low fuel pressure readings.
• Smart spares to fit together: new strainer/sock, tank seal, and, if applicable to your variant, the in-tank filter or pressure regulator.

Handy replacement pointers for the DIY-inclined: work in a well-ventilated area, disconnect the battery, and depressurise the system (pull the pump fuse/relay and crank). Lift the rear seat base to access the pump cover, label hoses and connectors, and avoid sparks. Replace the sealing O-ring, refit the locking ring evenly, then prime the system by cycling the ignition before starting. Always check for leaks and verify fuel pressure with a gauge to the spec in the Subaru manual for your VIN and engine.

If in doubt, a trusted workshop with Subaru experience can pressure-test the system and confirm whether it’s the pump, the relay, the fuel filter, or the regulator causing grief.

• Where is the fuel pump on a 2004 Impreza, and how long to replace?
  It’s inside the fuel tank under the rear seat base, accessed via an inspection cover. A first-time DIY job typically takes 1.5–3 hours. Workshops often knock it over more quickly if lines and locking rings aren’t corroded.
• Can a 2004 Impreza run E10, and does ethanol affect the pump?
  E10 is commonly accepted in AU/NZ for this model. Higher-ethanol fuels can increase pump wear unless the pump and hoses are rated accordingly. If running ethanol blends, monitor for noise and consider a compatible upgraded pump.
• What are the fuel pressure specs and how do you test?
  Specs vary by engine/market. Use a fuel pressure gauge on the feed line or rail as directed in the Subaru manual for your VIN. Test at key-on prime, idle, and under load. If pressure is low, confirm power/earth and the relay before condemning the pump.