What you're replacing and why it fails

The high pressure fuel pump in a 2017 Mazda CX-3 sits inside the fuel tank and pressurizes gasoline to around 2,000 PSI before it reaches the fuel injectors. When this pump fails, the engine won't start, stalls while driving, or runs rough because the injectors aren't receiving fuel at the correct pressure. A failing pump usually makes a whining noise from the tank before it stops working entirely.

Most 2017 CX-3 owners who need this replacement are dealing with a pump that has straightforward worn out after years of use. The pump can also fail if you've run the tank very low repeatedly, which starves the pump of the fuel it needs to cool itself. Replacing it means dropping the fuel tank, removing the old pump assembly, and installing a new one — a job that takes four to six hours if you're working in a driveway and have basic mechanical experience.

Key Takeaways

  • The high pressure fuel pump is located inside the fuel tank and must be accessed by removing the tank from underneath the vehicle.
  • You will need a fuel pump replacement kit (pump, seals, and strainer) specific to the 2017 CX-3, which costs between $300 and $500 for the part alone.
  • The job requires a fuel pressure gauge to confirm the pump is working after installation, a jack and jack stands for safety, and basic hand tools including a socket set.
  • Draining the fuel tank completely before you start prevents spills and reduces fire risk when you're working near the fuel system.
  • After installation, you must turn the ignition key to the "on" position three times without starting the engine to prime the new pump before attempting to start.

Gathering the right parts and tools

Order a fuel pump assembly kit designed for the 2017 CX-3 — do not buy a pump alone, because the kit includes the fuel strainer and rubber seals that wear out and need replacement. Mazda part number is available through dealership parts departments or aftermarket suppliers like RockAuto or Amazon. The kit typically costs $300 to $500 depending on whether you choose OEM (Mazda factory) or aftermarket. Aftermarket pumps from brands like Bosch or Airtex are reliable and cost less, usually $350 to $400.

For tools, you need a socket set (metric, since the CX-3 is Japanese), a fuel pressure gauge (around $30 to $50 if you don't own one), a jack rated for at least 4,000 pounds, jack stands, a drain pan for fuel, and a fuel line disconnect tool or a set of small screwdrivers to release the quick-connect fittings. A new fuel filter is optional but recommended — if you're already inside the tank, replacing the strainer is the time to do it. Have a fire extinguisher rated for fuel fires within arm's reach before you start.

Preparing the vehicle and draining the fuel

Park the CX-3 on level ground in a well-ventilated area — never work on fuel systems in a garage with the door closed. Disconnect the negative battery terminal to cut power to the fuel pump and prevent accidental sparks. Locate the fuel pump relay in the engine bay (consult your owner's manual for the exact location in the fuse box) and remove it. This disables the pump if the engine accidentally turns over while you're working.

Locate the fuel door on the driver's side rear quarter panel, open it, and unscrew the fuel cap. Place a drain pan under the fuel tank access point or the fuel line connection. If your CX-3 has a fuel drain plug on the tank, use it — otherwise, you'll need to siphon or use a fuel transfer pump to empty the tank into a safe container. Never siphon by mouth; use a hand pump or electric transfer pump. Drain until no fuel flows, then let the tank sit for 10 minutes to allow vapors to escape.

Removing the fuel tank and pump assembly

Raise the rear of the vehicle with the jack and find it on jack stands under the frame rails — never work under a vehicle supported only by a jack. Remove the rear wheels to access the undercarriage more easily. Locate the fuel tank straps (usually two metal bands bolted to the frame) and unbolt them using your socket set. Support the tank with a second jack or a helper before fully removing the straps, because the tank is heavy and will drop suddenly if unsupported.

Disconnect the fuel lines from the top of the tank by pressing the release tabs on the quick-connect fittings or using a fuel line disconnect tool. Disconnect the fuel pump electrical connector — it's a single plug on top of the tank. Carefully lower the tank with the jack until you can access the fuel pump access cover on top. The cover is a large circular or oval plate held down by bolts. Remove these bolts and lift the cover straight up. The pump assembly will come out with the cover; do not force it if it's stuck, as the rubber seal may need gentle rocking to break free.

Installing the new pump and reassembling

Before you install the new pump, inspect the rubber seal ring on the fuel tank opening. If it's cracked, hardened, or visibly damaged, it must be replaced — a leaking seal will cause fuel to drip into the vehicle. The new pump kit includes a fresh seal. Install the new seal first, then carefully lower the new pump assembly into the tank opening. The pump has a specific orientation; the fuel line connections must face the correct direction. Consult the kit instructions or your service manual for the exact orientation.

Bolt the access cover back down hand-tight, then use a torque wrench to tighten to the specification in your manual (typically 20 to 30 foot-pounds for the CX-3). Reconnect the fuel pump electrical connector and the fuel lines, making sure the quick-connect fittings click into place. Raise the fuel tank back into position, reconnect the straps, and tighten them securely. Reconnect the negative battery terminal and reinstall the fuel pump relay.

Priming the pump and testing for leaks

Before you start the engine, you must prime the new pump to fill the fuel lines with gasoline. Turn the ignition key to the "on" position (without starting the engine) and listen for a brief whining sound from the tank — this is the pump running. Turn the key back to "off," wait five seconds, then repeat this cycle two more times. On the third cycle, leave the key in the "on" position for 10 seconds. This fills the fuel lines and prevents the engine from cranking excessively when you start it.

Inspect the fuel tank area and all fuel line connections for drips or leaks while the pump is primed. If you see fuel pooling, turn the key off when ready and tighten the connection. Once you're confident there are no leaks, start the engine. It may take a few extra seconds to turn over because the fuel system is being pressurized for the first time. Let it idle for 30 seconds, then turn it off and wait five minutes. Restart it again to confirm it starts normally. If the engine starts and idles smoothly without hesitation or rough running, the pump is working correctly.

Confirming proper fuel pressure

To verify the pump is delivering fuel at the correct pressure, connect a fuel pressure gauge to the fuel rail test port (a small valve on the fuel rail in the engine bay). Consult your service manual for the exact location. With the engine running, the gauge should read between 50 and 60 PSI for the 2017 CX-3. If the reading is lower, the pump may not be fully primed or there may be an issue with the installation. If it's higher than 60 PSI, the fuel pressure regulator may need inspection.

If the pressure is within range, remove the gauge and reinstall the test port cap. Take the vehicle for a short test drive at moderate speeds to confirm the engine runs smoothly under load. Listen for any unusual noises from the fuel tank area and watch the dashboard for warning lights. If everything runs normally, the replacement is complete. Reinstall the rear wheels, lower the vehicle, and dispose of the old pump and fuel safely — many auto parts stores accept used fuel pumps for recycling.

Frequently Asked Questions

Can I replace the fuel pump without dropping the fuel tank?

No. The pump is mounted inside the tank and can only be accessed by removing the tank from the vehicle. Some vehicles have an in-cabin access panel, but the 2017 CX-3 does not. You must drop the tank to reach the pump assembly.

What happens if I don't prime the pump before starting the engine?

The engine will crank repeatedly without starting because the fuel lines are empty and the injectors have no fuel pressure. Priming fills the lines so the engine starts on the first or second turn of the key. Excessive cranking can drain the battery and strain the starter motor.

How long does the new pump last?

A quality replacement pump typically lasts 100,000 to 150,000 miles or more if the fuel tank is kept reasonably full and the fuel filter is changed on schedule. Running the tank very low repeatedly shortens pump life because the fuel cools the pump motor.

Can I reuse the old fuel lines and connectors?

The rubber fuel lines can be reused if they show no cracks or hardening, but the quick-connect fittings should be inspected. If they're loose or damaged, replace them. The fuel strainer inside the tank must always be replaced as part of the pump kit.

What should I do if fuel leaks after I reinstall the tank?

Turn off the engine when ready and do not start it again. Check that all fuel line connections are fully seated and clicked into place. Tighten the access cover bolts to the correct torque specification. If leaking continues, the rubber seal may be damaged and the tank may need to be dropped again to inspect and replace it.