September 2026

2009 Buick Lucerne Fuel Pump Relay Gets Hot: What It Means, Why It Happens, and How to Fix It for Good

The bottom line up front: If your 2009 Buick Lucerne fuel pump relay gets hot, you are looking at a well-documented design flaw, not a random electrical gremlin. This overheating is the early warning sign of a problem that can melt your fuse box, leave you stranded, and in the worst cases, start a fire. The most common root cause is physical pressure from the rear seat frame pressing down on the rear fuse box, which causes the relay to make poor contact, arc, and generate extreme heat. The second most common cause is a fuel pump that draws too much current, which burns out the relay from the inside. If you catch it early and address the root cause—not just the relay itself—you can prevent a repeat failure and keep your Lucerne reliable. Acting quickly is critical, because what starts as a hot relay can quickly turn into a melted fuse box, a damaged fuel pump, and a repair bill that jumps from $20 to over $800.

Why the Fuel Pump Relay Overheats in a 2009 Lucerne

On the 2009 Buick Lucerne, the fuel pump relay is not located in the engine bay. It is located in the Rear Underseat Fuse Block, specifically identified as Relay #59. The fuel pump fuse (Fuse #1, 20A MINI) is located in the same box. To access it, you remove the rear seat cushion by pulling up and forward, then remove a black plastic cover on the floor to expose the fuse block.

There are two distinct problems that cause this relay to overheat, and understanding both is the only way to get a permanent fix.

Problem 1: The Seat Bracket Crushing the Fuse Box

The most reported cause of overheating is a physical design flaw. The metal frame of the rear seat bottom sits so low that it makes contact with the top of the Rear Electrical Center (REC) cover. When passengers sit in the back, the seat frame presses down on the fuse box cover, which pushes against the fuel pump relay.

This pressure causes the relay to move or vibrate slightly while you drive. That movement creates resistance at the terminals. Resistance creates heat. Over time, the relay gets so hot that it melts the plastic housing of the relay itself and the surrounding fuse box slots. One owner described it as the power "arcing" and getting so hot that the relay started smoking and melting the fuse box and surrounding fuses.

General Motors acknowledged this issue in Service Bulletin 15-NA-051. The official correction was to install a low-profile fuel pump relay (Part Number 88953222) and, for Lucerne models specifically, to cut approximately 5mm off the driver-side mounting brackets of the rear seat frame to stop them from contacting the electrical center.

This is crucial: if you simply replace the melted relay with a standard one and do not trim the seat bracket, the new relay will crush and melt again within months.

Problem 2: The Fuel Pump Drawing Excess Current

The second cause is an electrical one. Some Lucerne fuel pumps draw more current than the relay circuit is designed to handle. This is often described as a short circuit or a current overload. When the pump draws too much amperage, the relay contacts overheat and burn out from the inside.

Several owners have reported that even after replacing the fuel pump relay, the new relay still gets red hot because the underlying pump is the source of the excess load. In one case, a mechanic tested the relay and found it was drawing 0.28 amps while idling, and within a minute the relay started to get really hot. Another owner reported that the fuel pump relay's prong base melted because the fuse current was at 10.01 amps for a 5-amp relay.

Either root cause—the seat pressure or the excessive pump draw—will result in the same symptom: a relay that gets dangerously hot.

Symptoms to Watch For

If your relay is overheating, you may notice one or more of the following signs. Catching these early can save you hundreds of dollars.

Engine cranks but won't start: The starter spins the engine, but it never fires up. You may not hear the fuel pump prime (a brief whirring sound) when you turn the key to the "ON" position.
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 immediately.
Intermittent starting problems: Sometimes the car starts fine, other times it won't. This happens when the relay's internal contacts are worn and only make a connection occasionally.
No fuel pump priming sound: When you turn the key to "ON" (without starting), you should hear a short whirring sound from the rear of the car. If you don't hear it, the relay likely isn't sending power to the pump.
Burning plastic smell or visible smoke: Many owners report a distinct "burning plastic" odor inside the cabin near the back seat. Some have even seen smoke coming from the seat area. This is a fire hazard and requires immediate action.

What Happens If You Ignore It

Ignoring a hot fuel pump relay is not an option. The heat will eventually melt the plastic fuse box, breaking the connection entirely. When this happens, the fuel pump receives no power, and the car will not start.

The damage is not limited to the relay. The heat can spread to surrounding fuses and the fuse box itself. Repair costs quoted by owners range from $400 to $850, depending on the extent of the damage. Some owners paid over $818 to replace the entire rear electrical center after the relay melted it. In severe cases, the melting has caused fires. There have been at least 15 fire-related complaints filed with NHTSA for this issue.

How to Diagnose the Problem

You can perform a visual inspection before spending any money on parts. Here is how to check if your relay is overheating.

Step 1: Access the fuse box. Lift the bottom cushion of the rear seat. It pulls up and forward with moderate force. You will see a black plastic cover on the floor.

Step 2: Remove the cover. This exposes the Rear Underseat Fuse Block. Look at the diagram on the inside of the cover to locate Relay #59 (the fuel pump relay).

Step 3: Inspect the relay and fuse box. Pull the relay out and look closely. Is the plastic around the pin slots melted, brown, or black? Are the relay legs scorched? If you see any discoloration or melting, your relay has already overheated to a dangerous level.

Step 4: Check the fuel pump's current draw. This is the step many people skip. If you have a multimeter, you can check the amperage draw of the fuel pump circuit. The relay should not be getting hot during normal operation. If it is, the pump is likely pulling too much current.

Step 5: Swap the relay with a known good one. There are other relays in the same fuse box with the same part number, such as the park lamps relay (#58) or the trunk release relay (#67). Swap them and see if the fuel pump works. If it does, your old relay was bad.

Permanent Fixes and Repair Options

There are two main ways to fix this issue: the official GM method and a more permanent bypass method.

The Official GM Repair (Short-Term Fix)

The official service bulletin (15-NA-051) instructs technicians to do two things:

Install a new low-profile fuel pump relay (Part #88953222). This gives more clearance under the fuse box cover.
For Lucerne models, cut approximately 5mm (0.197 in) off the driver-side seat mount bracket to prevent it from pressing on the electrical center.

This is the factory-recommended fix. However, many owners report that this only solves the problem if the fuel pump is not drawing excess current. Some owners who followed this procedure still experienced the relay overheating.

The Permanent Bypass (Smart & Cheap)

Many owners have solved the recurring overheating by moving the relay out of the fuse box entirely. You can buy a "Fuel Pump Relay Relocation Kit" that plugs into the melted slot but moves the actual relay to an external heavy-duty holder that hangs off to the side, away from the seat frame.

One owner described a DIY bypass: they used a 10mm wrench to turn the fuse box over, spliced two wires into the rear of the box (gray to #87 for the fuel pump, green/white to #86), and ran a 14-gauge wire to ground and a 14-gauge wire with a 20-amp fuse to 12V power. They moved the relay outside the box, and it ran at a normal temperature of 145 degrees instead of over 225 degrees. This approach eliminates the pressure problem and allows the relay to dissipate heat.

If you choose this route, it is essential to make sure you keep the relay away from the seat frame and allow for adequate airflow.

Why You Should Also Check the Fuel Pump

As mentioned above, the fuel pump itself can be the source of the excessive current draw. If you replace the relay and it still gets hot, the pump is the prime suspect. A failing fuel pump motor can start to draw excess amperage as its bearings wear out or it gets clogged.

A new relay will not fix an overloaded circuit. In this case, you need to replace the fuel pump. Repeating relay replacements without addressing the pump will just burn through more relays and risk melting your fuse box again.

Summary

The 2009 Buick Lucerne fuel pump relay overheating issue is a serious, known problem. The steps to resolve it are clear:

Address the physical pressure: Trim the rear seat bracket and install a low-profile relay to stop the seat from crushing the fuse box.
Test the fuel pump: Use a multimeter to check the current draw. If the pump is pulling too many amps, replace it with a high-quality unit like a KEMSO.
Consider relocating the relay: For the most robust solution, use a relay relocation kit to move the relay out of the fuse box and away from heat and pressure.

Do not wait. If your relay is hot, it is a ticking time bomb that will eventually leave you stranded or, worse, cause a fire. Diagnose it, fix the root cause, and you will have a reliable car again.

For more details on diagnosing your fuel system or to order a replacement fuel pump, visit the KEMSO website at https://www.kemsoracing.com/ .

Back to blog