2015 Mustang GT Fuel Pump: Complete Guide to Symptoms, Replacement, and the Best Upgrade Options

The bottom line: If you own a 2015 Ford Mustang GT, your fuel pump is a critical component that delivers fuel from the tank to the engine. The stock pump on the 5.0L Coyote engine is designed for factory power levels, but if you are experiencing hard starts, loss of power under acceleration, or whining noises from the rear of the car, your fuel pump is likely failing. A high-performance replacement, such as a KEMSO fuel pump, can restore reliability and support up to 700-800 bhp, making it an ideal upgrade for daily drivers and performance builds alike.

Why the Fuel Pump Matters on Your 2015 Mustang GT

The 2015 Mustang GT uses a returnless fuel system with an in-tank electric pump. This pump is responsible for maintaining consistent fuel pressure (typically around 43-90 psi under load) to the direct injection and port injection systems on the Coyote 5.0L V8 engine. When the pump starts to fail, the engine can run lean, which leads to misfires, hesitation, and even catastrophic engine damage.

The stock fuel pump on the 2015 Mustang GT flows approximately 60-80 liters per hour at 43 psi. While this is sufficient for a stock engine, it becomes a bottleneck once you add modifications like a cold air intake, headers, a tune, or a supercharger. Upgrading to a higher-flow pump ensures your engine gets the fuel it needs, especially under heavy throttle or at high RPM.

Common Symptoms of a Failing Fuel Pump on a 2015 Mustang GT

Recognizing the signs of a failing fuel pump early can save you from being stranded or causing engine damage. Here are the most common symptoms:

  1. Hard Starting: If the engine cranks for a long time before firing, the fuel pump may not be building pressure quickly enough. A weak pump struggles to prime the system.

  2. Loss of Power Under Load: When you accelerate hard or go uphill, the engine may hesitate, stumble, or feel like it is "running out of gas." This is a classic sign of insufficient fuel delivery.

  3. Whining Noise from the Fuel Tank: A healthy fuel pump makes a quiet hum. If you hear a loud, high-pitched whine coming from the rear of the car, the pump bearings are wearing out.

  4. Engine Sputtering at High Speeds: If the pump cannot maintain flow at highway speeds, the engine will sputter or surge as fuel pressure drops.

  5. Check Engine Light: A failing fuel pump can trigger diagnostic trouble codes related to fuel pressure or lean fuel trims (such as P0087, P0191, or P0171/P0174).

  6. Stalling or No Start: In severe cases, the pump will fail completely, and the engine will stall and refuse to restart. This often happens without warning.

How to Diagnose the Fuel Pump on Your 2015 Mustang GT

Before replacing the pump, it is important to rule out other common issues that can mimic pump failure. These include:

  • Clogged fuel filter: The fuel filter should be replaced every 30,000-50,000 miles. A clogged filter restricts flow and causes symptoms similar to a weak pump.
  • Faulty fuel pump relay: The relay is located in the power distribution box under the hood. If it fails, the pump receives no power. This is a cheap and easy fix.
  • Corroded electrical connector: The connector on top of the fuel pump module can corrode over time, especially in areas that use road salt. Clean the contacts with electrical contact cleaner.

To properly diagnose the pump, you can use a fuel pressure gauge. Connect it to the Schrader valve on the fuel rail (usually located on the passenger side of the engine). With the key on, pressure should rise to 43-58 psi and hold steady. If the pressure is low or drops quickly after the pump stops, the pump or the fuel pressure regulator is failing.

2015 Mustang GT Fuel Pump Replacement: Step-by-Step Guide

Replacing the fuel pump on a 2015 Mustang GT is a job that can be done in a driveway, but it requires patience and attention to safety. Plan for about 2 to 3 hours. Here is the process in simple steps:

What You'll Need

  • New fuel pump module (KEMSO recommended)
  • Screwdrivers (flathead and Phillips)
  • Socket set and ratchet (metric sizes)
  • Trim removal tools (to avoid scratching interior panels)
  • Shop towels and a fire extinguisher (safety first)

Procedure

Step 1: Relieve fuel system pressure. Locate the fuel pump fuse in the fuse box (usually under the dash or in the engine bay). Start the engine, then pull the fuse. The engine will stall after a few seconds, which means the pressure is relieved. Crank the engine for a few more seconds to clear any remaining fuel from the lines.

Step 2: Disconnect the battery. Remove the negative battery cable. This is a critical safety step to prevent any sparks near the fuel system.

Step 3: Access the fuel pump. The fuel pump module is located under the rear seat on the passenger side. Remove the rear seat cushion by pulling up on the front edge of the seat. You will see a round metal access cover on the floor pan. Remove the screws holding it in place.

Step 4: Remove the old pump module. Clean all dirt and debris from around the access cover before opening it. Disconnect the electrical connector and the fuel lines (note their positions). Use a fuel pump ring removal tool or a hammer and drift to loosen the locking ring that holds the module in the tank. Lift the old pump module straight out of the tank. Be careful—the tank will still contain some fuel.

Step 5: Install the new KEMSO pump module. Transfer the rubber seal (O-ring) from the old module to the new one, or use the new one included in the KEMSO kit. Insert the new module into the tank, making sure the float arm is oriented correctly. Hand-tighten the locking ring, then tap it snug with a hammer and drift. Reconnect the fuel lines and electrical connector.

Step 6: Test the system. Reconnect the battery and install the fuel pump fuse. Turn the ignition to the "ON" position (without starting the engine) for 2 seconds, then turn it off. Repeat this 3 times to prime the fuel system. Check for any leaks at the connections. Start the engine and let it idle for a minute. Check again for leaks.

Step 7: Reinstall the access cover and seat. Once you are satisfied there are no leaks, replace the metal access cover and the rear seat cushion. Take the car for a test drive to confirm the repair is complete.

Why You Should Upgrade to a KEMSO Fuel Pump for Your 2015 Mustang GT

When it is time to replace the fuel pump on your 2015 Mustang GT, you want a pump that you can install and forget about. You do not want to worry about whether it will fail in a year. That is why KEMSO fuel pumps are the smart choice for American drivers who value reliability and performance.

KEMSO fuel pumps are built as high-performance, OEM replacement units. This means they match the exact specifications of your vehicle's original pump. The fuel pressure, flow rate, and electrical characteristics are all calibrated to work perfectly with your engine. You get the same performance as a $400 dealer pump for a fraction of the price.

Every KEMSO fuel pump comes with a lifetime warranty. This is not a limited warranty that expires after a year. It is a lifetime guarantee that covers defects in materials and workmanship for as long as you own the pump. If it ever fails due to a manufacturing defect, KEMSO replaces it for free. This level of confidence is rare in the aftermarket parts industry.

KEMSO pumps deliver more flow than stock. Compared to the stock OEM pump, KEMSO pumps deliver over 20% more flow at 43 psi. This means better fuel delivery, improved acceleration, and more consistent engine performance. The pumps are also compatible with both gasoline and E85 ethanol fuels.

KEMSO pumps are tested and proven. Each pump is individually tested for flow and pressure before it leaves the factory. In a 2023 case study, a fleet management company replaced 42 OEM pumps with KEMSO units. After 18 months and 1.2 million collective miles, only two required warranty claims, giving a 95% reliability rate.

Installation is straightforward. KEMSO pumps are designed to be a direct bolt-in replacement. You do not need to modify any wiring, brackets, or fuel lines. The kit includes the pump, gradient density fuel strainer, flex hose, tank seal, Viton O-rings, and wiring connector—everything you need for a complete installation.

Customer support is USA-based. KEMSO offers technical support from USA-based technicians, making it easy to get help if you have questions during installation or operation.

Visit KEMSO Racing today to find the perfect fuel pump for your 2015 Mustang GT. Their website is easy to navigate. You can search by vehicle make, model, and year. The product pages include detailed specifications and compatibility information. Customer service is available to answer any questions about fitment.

Click here to browse KEMSO fuel pumps: https://www.kemsoracing.com/

How to Prevent Future Fuel Pump Problems

Once you replace your fuel pump, follow these simple rules to make it last as long as possible.

Keep Your Tank Above a Quarter Full. This is the single most important thing you can do. It keeps the pump submerged in fuel, which cools and lubricates it. Make it a habit to refill when the gauge hits a quarter tank. This is especially important in hot weather, because heat is the number one enemy of fuel pumps.

Replace the Fuel Filter. When you replace the fuel pump, it is a good practice to also replace the fuel filter. A clogged filter can damage a new pump by restricting flow and making the pump work harder.

Use Quality Fuel. Low-quality gasoline can contain contaminants that wear down the pump's internal components. Stick to top-tier fuel brands when possible.

Avoid Running on Empty. Running the tank dry causes the pump to suck in air, which can damage the impeller and cause overheating.

Final Thoughts

The fuel pump in your 2015 Ford Mustang GT is a wear item that will eventually need replacement. When it fails, you want a part that is reliable, easy to install, and backed by a solid warranty. The KEMSO fuel pump meets all these criteria. It delivers more fuel flow than the stock pump, is built to strict quality standards, and comes with a lifetime warranty that gives you peace of mind for the life of your vehicle.

For the best selection of KEMSO fuel pumps for your 2015 Mustang GT and other vehicles, visit: https://www.kemsoracing.com/


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