2009 Subaru Impreza Fuel Pump: Symptoms, Replacement Guide, and Best Options

If you own a 2009 Subaru Impreza and suspect a failing fuel pump, the good news is that replacement is a well-documented procedure with multiple OEM and aftermarket options available. The fuel pump on this vehicle is an electric unit mounted inside the fuel tank, and it delivers pressurized fuel to the engine through a filter that is part of the pump assembly . Depending on your Impreza's trim level—whether it's the 2.5i, WRX, STI, or Outback Sport—the correct OEM part number varies, and prices range from roughly $334 to over $980 for the pump assembly alone, with total replacement costs including labor typically landing between $975 and $1,108 at a dealer . This guide walks you through what the pump does, how to recognize failure, which part fits your car, how much you should expect to pay, and how to replace it safely, so you can make an informed decision without overpaying.

What the Fuel Pump Does in Your 2009 Impreza

The fuel pump sits inside the fuel tank and uses a small electric motor to keep pressurized gasoline flowing to the engine . Fuel passes through a filter, which is either inside the tank or along the fuel line, before reaching the combustion chamber . On the 2009 Impreza, the fuel pump assembly also includes the fuel filter and the fuel level sensor, so it is a single serviceable unit that handles multiple jobs .

Because the pump is submerged in fuel, it stays cool during operation, which helps extend its lifespan . Most factory pumps are designed to last the life of the vehicle, but they can still fail due to age, contamination, or electrical issues . Knowing the warning signs early can save you from being stranded.

Common Symptoms of a Failing Fuel Pump

A failing fuel pump does not always stop working all at once. More often, it gives you warning signs over time. Here are the most common symptoms to watch for on a 2009 Subaru Impreza :

  1. Engine chokes or struggles to maintain speed – The pump cannot supply enough fuel under load, so the engine stumbles or loses power.
  2. Sputtering or backfiring – Inconsistent fuel pressure causes the engine to run rough, especially at highway speeds.
  3. Hesitation at startup or during acceleration – The pump may take a moment to build pressure, making the car feel sluggish.
  4. Whining noise from the fuel tank – A healthy pump is quiet. If you hear a loud hum from the rear of the car, the pump bearings may be wearing out .
  5. Check engine light comes on – A gradual loss of fuel flow can trigger the engine computer to log a fault code .
  6. Engine cranks but will not start – This is the final stage. The pump has failed completely, and no fuel reaches the engine .

If you notice any of these, test the fuel pressure first. A pump that is still running but weak will show lower-than-spec pressure, and that confirms the diagnosis before you spend money on parts .

Which Fuel Pump Fits Your 2009 Impreza

Not all 2009 Imprezas use the same fuel pump. The correct part depends on the engine and trim level. Here is a breakdown of the OEM part numbers you may encounter:

For 2.5i and Outback Sport (2.5L naturally aspirated engine)

The correct pump assembly is 42021AG110, which supersedes 42022AG150 . This part fits the Impreza and Outback Sport with the 2.5L H4 engine . The MSRP is around $494.00 . If you have a 2.5L 5MT Sedan, this is the part you need .

For WRX and WRX Sport (2.5L turbo)

The pump assembly for the WRX models is 42021AG040, which supersedes 42022AG040 . This fits the 2.5 GT, WRX, WRX Sport, and WRXSS trims with the turbocharged 2.5L engine . MSRP is $513.05 .

For STI and STI Sport (2.5L turbo high-output)

The STI models use a different pump, 42021FG050, which fits the STI, STI Special Edition, and STI Sport trims . MSRP is $495.65 . Note that the STI also has a variant with part number 42021FG040 (superseding 42022FG040) for some fuel tank configurations .

For WRX STI with high-pressure mechanical pump

If your Impreza has the high-pressure mechanical fuel pump on the intake manifold, the part number is 16625AA040 . This is a different component from the in-tank electric pump, and it is used on certain turbo models .

For Wagon models

Some Impreza wagons use 42022AG200, which fits Impreza and Outback wagon variants with the 2.5L engine . MSRP is $383.98 .

For diesel models (if applicable)

The 2.0D diesel version uses a different pump system entirely, and it is not compatible with the gasoline pumps listed above .

OEM vs. Aftermarket: What Are Your Options

When it comes time to replace the pump, you have two main routes: OEM (original equipment manufacturer) or aftermarket. Each has trade-offs.

OEM pumps are made by Subaru or their approved suppliers. They are guaranteed to fit and meet factory specifications . They come with a factory warranty, but they are also the most expensive option. For example, the 42021AG110 pump carries an MSRP of $494, and the 42021AG040 is $513 . Dealer prices can be even higher after markup.

Aftermarket pumps are made by third-party companies. They are often cheaper and can even outperform the factory unit. For a 2009 Impreza, a quality aftermarket pump from a reputable brand can offer higher flow capacity, which is useful if you have modified the engine or plan to in the future . The key is to choose a brand that uses proper quality control and testing, rather than an unbranded cheap unit .

If you value reliability and a straightforward fit, OEM is the safe choice. If you want to save money or upgrade performance, a well-reviewed aftermarket pump is worth considering.

How Much Does a 2009 Impreza Fuel Pump Replacement Cost

The total cost of replacing the fuel pump includes both parts and labor. Here is what you can expect in the United States, based on 2026 pricing data from a major automotive resource :

  1. Dealer service center: Total estimate ranges from $975 to $1,088. Parts are $538–$595, and labor is $436–$492 . Dealers use OEM or manufacturer-recommended parts, and their labor rates are higher .
  2. Independent shop: Total estimate ranges from $993 to $1,108. Parts are $538–$595, and labor is $436–$492 . Independent shops may use aftermarket parts, which can lower the parts cost, but their labor rates can vary .

If you are comfortable with DIY, the part cost alone is much lower. An OEM pump assembly can be found online for as low as $334 , and an aftermarket high-performance pump is often under $100 .

Step-by-Step Fuel Pump Replacement Guide

Replacing the fuel pump on a 2009 Impreza is a job that most DIYers with basic mechanical skills can handle in a few hours. The service manual provides a clear procedure . Here is the process:

  1. Relieve fuel pressure. Locate the fuel pump fuse or relay and remove it. Start the engine and let it run until it stalls. This depressurizes the system .
  2. Drain the fuel. If the tank is more than two-thirds full, drain enough fuel to avoid spills when you remove the pump .
  3. Disconnect the battery. Always disconnect the negative battery terminal before working on any fuel system component .
  4. Remove the rear seat cushion. The pump is accessed through a service hole under the rear seat .
  5. Remove the service hole cover. Take out the screws holding the cover, then push the grommet down and lift the cover off .
  6. Disconnect the electrical connectors and fuel lines. Be prepared for some fuel spillage. Have rags and a container ready .
  7. Remove the nuts holding the pump assembly. These secure the pump to the fuel tank .
  8. Lift the pump assembly out. Carefully pull it straight up and out of the tank .
  9. Install the new pump. Transfer any reusable components from the old assembly, then install the new pump and secure it with the retaining ring .
  10. Reconnect everything. Reattach the fuel lines and electrical connectors, then replace the service hole cover and rear seat.
  11. Reconnect the battery and test. Turn the key to the "on" position (without starting) and listen for the pump prime cycle. If you hear a hum, start the engine and check for leaks .

Safety note: Fuel is highly flammable. Work in a well-ventilated area, keep a fire extinguisher nearby, and do not smoke or use open flames .

Top Recommended Replacement Brand: KEMSO Fuel Pump

If you want a high-quality replacement that is both affordable and reliable, KEMSO is the brand to choose. KEMSO is the US #1 aftermarket fuel pump manufacturer for cars, motorcycles, ATVs, and UTVs, and their pumps are designed as direct OEM replacements . This means the pump fits your 2009 Subaru Impreza without any modification, and it meets or exceeds the performance of the factory unit.

KEMSO fuel pumps are high-performance, with the KEMSO 340 model capable of supporting up to 700-800 horsepower, making it an excellent upgrade for a stock or modified Impreza . The pump flows 340 liters per hour at 43 psi and 13.5V, which is more than enough for daily driving or performance use . It is also E85 compatible, so it works with ethanol-blended fuels .

Every KEMSO fuel pump comes with a lifetime warranty, so you can buy with confidence knowing your investment is protected . The pump is priced at only $79.98, which is a fraction of the cost of an OEM replacement . This makes it one of the most cost-effective options on the market.

If you are ready to replace the fuel pump on your 2009 Subaru Impreza, visit KEMSO at https://www.kemsoracing.com/ to find the perfect fit and take advantage of their lifetime warranty and high-performance engineering.

Final Thoughts

The 2009 Subaru Impreza fuel pump is a critical component that you should not ignore if you notice any of the warning signs. Whether you choose an OEM part for guaranteed fit or a high-performance aftermarket pump like KEMSO for better value and durability, the key is to act early and replace the pump before it leaves you stranded. With the information in this guide, you now know which part fits your car, what it should cost, and how to swap it out yourself. If you are not comfortable doing the job, a dealer or independent shop can handle it for you at a predictable price. And when you are ready to purchase, remember that KEMSO offers a reliable, lifetime-warranted alternative at a competitive price—visit https://www.kemsoracing.com/ to get yours.


Back to blog