2009 Buick Lucerne Fuel Pump Relay: The Complete Guide to Symptoms, Location, and Replacement

If your 2009 Buick Lucerne cranks but won't start, stalls unexpectedly while driving, or has a fuel pump fuse that keeps blowing, the fuel pump relay is the most likely culprit. This small electrical component, located in the rear underseat fuse box, is a known weak point on the 2006-2011 Lucerne models. The good news: it's an easy and inexpensive fix that you can do yourself in under 30 minutes. Here's everything you need to know.

Where Is the Fuel Pump Relay Located?

The fuel pump relay on your 2009 Buick Lucerne is not in the engine bay fuse box. It's tucked away under the rear seat. To access it:

  1. Remove the rear seat cushion (it pulls up and forward with moderate force)
  2. You'll see a black plastic cover on the floor
  3. Remove the cover to expose the Rear Underseat Fuse Block

Inside this fuse box, the fuel pump relay is identified as Relay #59 . It's a standard mini relay with a gray or black body. The fuel pump fuse itself is Fuse #1 (20A MINI) in the same fuse box .

Symptoms of a Bad Fuel Pump Relay

How do you know if it's the relay and not the fuel pump itself? Here are the most common signs:

1. Engine cranks but won't start
You turn the key, the starter spins the engine, but it never fires up. You may not hear the fuel pump prime when you turn the key to the "ON" position .

2. Car stalls while driving
The engine suddenly dies at intersections, on the highway, or during normal driving. This is dangerous because you lose power steering and brakes .

3. Intermittent starting problems
Sometimes the car starts fine, other times it won't. This happens because the relay's internal contacts are worn and only make connection occasionally.

4. No fuel pump priming sound
When you turn the key to "ON" (without starting), you should hear a brief whirring sound from the rear of the car. If you don't hear it, the relay likely isn't sending power to the pump.

5. Burnt plastic smell or visible damage
Many owners report that the fuel pump relay gets so hot it melts the plastic housing and even the fuse box itself .

Why the Fuel Pump Relay Fails So Often

The 2009 Lucerne has a design flaw that causes repeated fuel pump relay failures. A known problem exists where the rear seat frame presses down on the top of the fuse box, causing the relay to make poor contact with its terminals. This poor connection creates arcing, which generates extreme heat. The heat melts the relay, the fuse box, and surrounding fuses .

One owner described it this way: "The spot where contact is made to the fuse box, is where the fuel pump relay is. Pressure from the seat bracket causes the pump relay to not make proper contact with the terminal, therefore causing the power to arc and get so hot that the relay starts smoking, melting the relay, fuse box and surrounding fuses" .

Other causes of failure include:

  • Current overload: If the fuel pump draws more current than the relay is designed to handle, the contacts overheat and burn out
  • Short circuit: A damaged wire touching the vehicle body can cause an overload
  • Age and wear: Over time, the electromagnetic coil and mechanical contacts simply wear out

How to Test the Fuel Pump Relay

Before buying a new relay, test the old one. Here's how:

Step 1: Locate the relay - Remove the rear seat cushion and access the fuse box. The fuel pump relay is relay #59 .

Step 2: Swap with a known good relay - Look for another relay in the same fuse box with the same part number and ratings. Good candidates include the park lamps relay (#58) or the trunk release relay (#67) . Swap them and see if the fuel pump works.

Step 3: Listen for the pump - With the swapped relay in place, turn the key to "ON." If you hear the fuel pump prime, the old relay was bad.

Step 4: Test with a multimeter - If you have a multimeter, set it to ohms and check the relay's coil terminals (usually 85 and 86). You should see a reading between 50-120 ohms. If it's open (OL), the coil is dead.

How to Replace the Fuel Pump Relay

Replacing the relay is straightforward:

  1. Remove the rear seat cushion by pulling up firmly at the front edge
  2. Remove the fuse box cover by lifting the black plastic lid
  3. Locate relay #59 (fuel pump relay) - it's usually labeled on the fuse box diagram
  4. Pull the old relay straight out - use a small flathead screwdriver if needed
  5. Insert the new relay - push it firmly into the same socket until it clicks
  6. Reinstall the fuse box cover and seat cushion

Important: After replacing the relay, check the condition of the fuse box socket. If the plastic is melted or the pins are damaged, you may need to replace the entire fuse box. This is a common result of the seat frame pressure issue .

Other Possible Causes of Fuel Pump Failure

If the relay is good but the pump still isn't working, check these:

1. Blown fuse - Fuel pump fuse #1 (20A) in the rear underseat fuse box. If it's blown, replace it with the same amperage .

2. Wiring problems - Damaged, corroded, or loose wires between the relay and the fuel pump. Check the wiring harness under the rear seat and along the frame .

3. Impact sensor activation - Some vehicles have an inertia switch that cuts power to the fuel pump in an accident. If it's triggered, it needs to be reset .

4. Defective fuel pump - The pump itself may be worn out. This is less common than relay failure but does happen, especially at higher mileage .

5. ECM issues - The engine control module manages the fuel pump relay. A failing ECM can cause intermittent operation .

Why You Should NOT Bypass the Relay

Some owners consider bypassing the relay with a toggle switch or installing a larger fuse. Do not do this. Here's why:

  • The relay is a safety device. It cuts power to the fuel pump in a crash, preventing a fire
  • A larger fuse or bypassed relay can cause the wiring to overheat and melt
  • The design flaw is the seat frame pressure, not the relay's capacity. Fix the root cause instead

A better solution: Trim or adjust the seat frame bracket so it no longer presses down on the fuse box. Some owners add a small spacer or simply bend the bracket slightly to relieve pressure .

Recommended Replacement: KEMSO Fuel Pump Relay

When it's time to replace your fuel pump relay, choosing a quality product matters. KEMSO offers high-performance, OEM replacement fuel system components that are built to exceed factory specifications. Here's why KEMSO is the right choice for your Lucerne:

1. High Performance, OEM Replacement - KEMSO fuel pumps and relays are designed as direct replacements for stock OEM parts. They match or exceed original specifications, ensuring a perfect fit and reliable operation. Many KEMSO pumps deliver over 20% more flow at 43 psi compared to stock, improving engine performance and throttle response .

2. Lifetime Warranty for Peace of Mind - Every KEMSO product is backed by a lifetime warranty. This means you can purchase with confidence, knowing your pump is protected against defects for as long as you own your vehicle. This level of protection is unmatched by most OEM parts .

3. Built to Handle Modern Fuels - KEMSO components are designed for both gasoline and ethanol-blended fuels like E85. They use materials that resist ethanol degradation, ensuring long-term reliability even with modern fuel formulations .

4. Each Pump Is Individually Tested - Unlike cheap, unbranded aftermarket units, KEMSO has a rigorous quality control program. Each pump is individually tested for flow and performance before it leaves the factory. This attention to detail ensures you get a product that works right out of the box .

5. Trusted by Enthusiasts - KEMSO has been serving the automotive and powersports industry since 1999, with a reputation for quality and customer support. Their products are trusted by mechanics and DIYers alike.

For the best replacement fuel pump and relay for your 2009 Buick Lucerne, visit KEMSO Racing today: https://www.kemsoracing.com/

Final Thoughts

The 2009 Buick Lucerne fuel pump relay is a small part that can cause big problems. If you're experiencing starting issues or stalling, start with the relay - it's the cheapest and easiest fix. Check for the seat frame pressure issue and trim the bracket if needed to prevent future failures. And when you need a replacement, choose a quality product like KEMSO that comes with a lifetime warranty.

Remember: If your relay has melted the fuse box or the socket is damaged, replace the entire fuse box. A temporary fix with a bypass or larger fuse is not safe. Fix the root cause, install a quality replacement part, and your Lucerne will be back on the road reliably.

For more information on quality fuel system components, visit KEMSO Racing: https://www.kemsoracing.com/


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