2009 Ford Focus Fuel Pump Relay Location: A Complete Owner’s Guide

The bottom line up front: On a 2009 Ford Focus, the fuel pump relay is located inside the engine compartment fuse box (also called the power distribution box), which sits in the engine bay near the battery. It is specifically labeled as position 31B in the fuse box diagram. If your Focus cranks but won’t start and you suspect the fuel pump isn’t getting power, the relay is one of the first things you should check before spending money on a new pump.

This guide walks you through exactly where to find the relay, how to test it, how to replace it, and what else could be causing your fuel delivery problem. Everything here is based on the factory owner’s manual and real-world repair experience, so you can trust it whether you’re a first-time DIYer or a seasoned home mechanic.

Where the Fuel Pump Relay Is Located

The 2009 Ford Focus has two fuse boxes: one inside the cabin and one under the hood. The fuel pump relay lives in the under-hood fuse box, which Ford officially calls the “power distribution box.” This black box sits in the engine compartment, close to the battery.

Here’s how to get to it:

  1. Open the hood and look near the battery on the driver’s side of the engine bay. You’ll see a black plastic box with a cover.
  2. Remove the cover by lifting the release tabs. On the underside of the cover, you’ll find a diagram that labels each fuse and relay.
  3. Find position 31B on the diagram. That’s the fuel pump relay. It is one of several small, square relays mounted in a row inside the box.

The fuel pump relay in the 2009 Focus is a standard 4-pin or 5-pin automotive relay, roughly one inch wide, with metal prongs on the bottom. It sits next to other relays such as the reverse lamp relay (31A), the wiper power relay (31C), and the starter relay (30B).

One thing worth noting: some sources describe the fuel pump relay as being “above the horn relay” inside the engine fuse box, and that matches the 31B position in the factory diagram.

How the Fuel Pump Relay Works

The fuel pump relay is a small electromechanical switch. When you turn the ignition key to the ON position, the relay closes and sends battery voltage to the fuel pump. The pump then primes the fuel system by building up pressure, which is why you normally hear a brief humming sound from the rear of the car for a couple of seconds before you start the engine.

When the engine is running, the relay stays closed so the pump continues delivering fuel. When you turn the key off, the relay opens and cuts power to the pump. This design protects the electrical circuit and prevents the pump from running when it’s not needed.

If the relay fails, the fuel pump gets no power, no fuel pressure builds up, and the engine will crank but won’t start. The pump itself might be perfectly fine, which is why testing the relay before replacing the pump can save you a lot of money.

Symptoms of a Bad Fuel Pump Relay

A failed fuel pump relay produces symptoms that are nearly identical to a dead fuel pump. Here are the most common signs :

  1. Engine cranks but won’t start — This is the most obvious symptom. The starter turns the engine over, but there’s no fuel pressure, so the engine never fires up.
  2. No fuel pump prime sound — When you turn the key to ON, you normally hear a brief whirring or humming from the fuel tank area. If you hear nothing, the relay may not be sending power to the pump.
  3. Engine stalls while driving — If the relay fails intermittently, the engine can lose power and stall without warning, then refuse to restart.
  4. Hard starting after the car sits — A weak relay may work sometimes but not others, making the car difficult to start periodically.

Keep in mind that a bad fuel pump, a blown fuel pump fuse, a tripped inertia switch, or a wiring problem can all cause the exact same symptoms. So before you buy anything, take a few minutes to check the relay and the other easy items described below.

How to Test the Fuel Pump Relay

You don’t need to be an electrician to test a relay. Here are two simple methods that work in your driveway.

Method 1: Swap test (the easiest, no tools required)

This is the fastest way to tell if the relay is bad :

  1. Open the engine fuse box and locate the fuel pump relay at position 31B.
  2. Find another relay in the same fuse box that has the same part number stamped on its body. The A/C clutch relay (position 20), rear defrost relay (21A), blower relay (21C), and PCM relay (21D) are all likely candidates.
  3. Pull the fuel pump relay out, and swap it with one of those identical relays.
  4. Turn the key to ON and listen for the fuel pump prime sound. If you hear it, the original relay was bad.
  5. Start the engine. If it starts, you’ve found the problem.

If the car starts with the swapped relay, buy a replacement fuel pump relay and put the other relay back where it belongs.

Method 2: Multimeter test (more precise)

If you want to confirm the relay is bad before swapping parts, use a digital multimeter :

  1. Pull the relay out of the fuse box.
  2. Set the multimeter to measure resistance (ohms).
  3. Test the relay’s coil terminals — you should see a resistance reading typically between 50 and 120 ohms. If you get infinite resistance (no reading), the coil is burned out.
  4. Test the switch terminals for continuity. With the relay unpowered, the switch contacts should be open (no continuity). If you have continuity, the relay is stuck closed.

A relay that fails either test should be replaced.

How to Replace the Fuel Pump Relay

Replacing the relay is a five-minute job that requires zero special skills. Here’s the step-by-step process :

  1. Turn the ignition off and open the hood.
  2. Disconnect the negative battery cable for safety, especially if you’re working around other electrical components.
  3. Remove the fuse box cover and locate the fuel pump relay at position 31B.
  4. Pull the old relay straight out of its socket. It’s held in by friction, so a firm tug is all it takes. If it’s tight, gently rock it back and forth while pulling.
  5. Compare the new relay with the old one — the part number and pin layout must match. A standard automotive relay rated for 12 volts and 10–20 amps is what you need.
  6. Push the new relay firmly into the socket until it seats fully. You should feel it click into place.
  7. Reconnect the battery, turn the key to ON, and listen for the fuel pump prime sound.
  8. Start the engine and confirm it idles smoothly.

The whole process typically takes between 15 and 30 minutes, and the relay itself costs anywhere from $10 to $50 depending on where you buy it.

What Else to Check If the Relay Isn’t the Problem

If you replace the relay and the car still won’t start, don’t assume the fuel pump is dead. Work through these checks in order — each one takes less than ten minutes :

1. Check the inertia switch (fuel shutoff switch)

Ford vehicles, including the Focus, have a safety device called an inertia switch that cuts power to the fuel pump if the car is involved in a collision. A hard bump or a rough road can sometimes trip it accidentally. When tripped, the engine cranks but won’t start, and you won’t hear the fuel pump prime. It is indistinguishable from a dead pump.

On most Ford models, the inertia switch is located in the passenger footwell, under the dash, or behind a kick panel. Look for a small cylindrical or rectangular button, often with a red or white reset top. Press it firmly until it clicks, then try starting the car. If it starts, that was the problem.

2. Check the fuel pump fuse

Inside the engine fuse box, position 4 is a 20-amp fuse labeled “Fuel pump.” Pull it out and inspect it. If the metal element inside is broken or the glass is discolored, the fuse is blown. A blown fuse is a $1 fix — just replace it with another 20-amp fuse of the same type.

3. Check for voltage at the fuel pump

If the relay and fuse are both good, use a multimeter to check that power is actually reaching the fuel pump. With the key in the ON position, you should see 12 to 14 volts at the pump connector, which is usually accessible through an access panel under the rear seat or in the trunk. Less than 11 volts indicates a wiring or ground problem.

4. Check the fuel filter

A severely clogged fuel filter can cause symptoms identical to a failing pump: loss of power under acceleration, hesitation at highway speed, and difficulty starting. If the filter hasn’t been replaced in 30,000 miles or more, replace it before you condemn the pump.

Only after all these checks come up clean should you consider replacing the fuel pump itself.

Common Causes of Relay Failure

Fuel pump relays don’t fail very often, but when they do, the usual culprits are :

  1. Current overload — If the fuel pump or another part of the electrical system draws more current than the relay is rated for, the relay contacts overheat and burn out.
  2. Short circuit — A damaged wire touching the body or another wire can send a surge through the relay, frying its internal components.
  3. Normal wear — Relays are mechanical parts. The electromagnetic coil and the contacts wear out over time from repeated use, vibration, and age.

If the relay failed because of a short circuit or an overloaded pump, simply replacing the relay may not fix the problem for long. If your new relay fails quickly, have a mechanic inspect the fuel pump wiring and current draw.

Why the Fuel Pump Relay Matters for Your 2009 Focus

The 2009 Ford Focus is known as a reliable, economical compact car. The 2.0-liter four-cylinder engine is simple and sturdy, and routine maintenance is straightforward. But like any car that’s now more than 15 years old, electrical components such as relays can wear out.

The fuel pump relay sits in a position where it’s exposed to under-hood heat and vibration for the life of the vehicle. Knowing where it is and how it works can save you a tow bill and a costly trip to the shop. The relay is a $10–$50 part. The fuel pump, by comparison, can cost $300–$800 including labor. Checking the relay first is simply smart money management.

Recommended Replacement Fuel Pump: KEMSO

If you’ve confirmed that your fuel pump itself is the problem, you want a replacement that’s reliable, durable, and backed by a solid warranty. That’s why we recommend the KEMSO brand fuel pump.

KEMSO fuel pumps are built as high-performance, OEM replacement units, meaning they meet or exceed the original factory specifications for your vehicle. They are designed for a perfect fit and long service life, and every KEMSO pump is backed by a lifetime warranty. Whether you drive a Ford, a BMW, a Subaru, a Honda, or a Kawasaki, KEMSO has a pump that fits your application.

If your 2009 Ford Focus needs a new fuel pump, it makes sense to choose a brand that stands behind its product. KEMSO’s lifetime warranty gives you peace of mind that your replacement pump will keep your car running for years to come.

Visit KEMSO online to browse their full lineup of high-performance fuel pumps:

https://www.kemsoracing.com/

Final Thoughts

To sum it up: the fuel pump relay on a 2009 Ford Focus is in the engine compartment fuse box, at position 31B, and it’s easy to test and cheap to replace. If your car cranks but won’t start, check the relay, the fuse, the inertia switch, and the wiring before you buy a new pump. A $15 relay can save you hundreds of dollars in unnecessary repairs.

But if the fuel pump itself is truly dead, choose a KEMSO replacement for a high-performance, OEM-quality part with a lifetime warranty. You’ll find the right pump for your Focus at https://www.kemsoracing.com/ .


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