Why won't my Buick Lucerne start? (fuel pump relay under the back seat)

Short answer: On the Lucerne, a common cause of a crank-no-start is the fuel pump relay in the fuse box under the rear seat, behind the driver. The seat frame can press on the box, the relay loses good contact, gets hot and melts. GM's bulletin fix is a low-profile relay and trimming a small piece of the seat bracket. If the fuse box socket is melted, it needs replacing too.

Symptom: The engine cranks but won't fire; you don't hear the fuel pump hum when you turn the key; the relay or fuse box under the rear seat looks scorched or melted; a new relay works for a few miles and then melts again.

What to check first

1. Lift the rear seat cushion on the driver's side and look at the fuse/relay box next to the battery. A browned or melted fuel pump relay is the giveaway.
2. Check the socket, not just the relay. If the plastic or pins are melted, a new relay alone won't last.
3. Ask a Buick dealer about bulletin 15-NA-051 (low-profile relay and seat bracket trim).
4. Don't replace the fuel pump first. Rule out the relay, which is far cheaper.

Likely causes

1. Seat frame pressing on the fuel pump relay. The root cause in GM's bulletin and owner reports.
2. Melted or loose fuse box socket. Heat softens the pins, so new relays keep overheating.
3. Failed fuel pump. Possible, but rule out the relay first.

What it usually costs

One owner said a dealer did the bulletin fix for $141, with the relay about $18 and the rest labor. Another paid about $700 on the road for a fuel pump and a makeshift fix, then fixed his own car with a $35 used fuse block and a $6 relay. Prices are from owner posts.

Is it safe to keep driving?

A no-start isn't a road hazard by itself, but if it dies while driving it can stall in traffic, and a relay hot enough to melt plastic is a fire risk. Get it fixed before relying on the car. Verify with a mechanic.

DIY or shop?

DIY for most owners. Swapping the relay, a used fuse block and trimming the bracket are basic hand-tool jobs. Disconnect the battery first. A shop or dealer can do the bulletin repair if you'd rather not cut metal.

Recalls, bulletins and complaints in plain words

• Service bulletin: GM bulletin 15-NA-051 covers a no-start on the Lucerne caused by the rear seat frame contacting the fuel pump relay. The fix is a low-profile fuel pump relay and trimming about 5 mm from the seat bracket (bulletin PDF). A bulletin tells dealers how to fix a known problem; it isn't a recall, so you may have to pay.
• Related recalls: NHTSA lists these recalls touching this area of the Buick Lucerne: 08V441000 (2006-2008 model years, electrical system); 10V240000 (2006-2009 model years, electrical system); 10V553000 (2010-2011 model years, electrical system); 14V355000 (2006-2011 model years, electrical system). Check your VIN at nhtsa.gov/recalls. If your car is part of this recall, the dealer fixes it for free.
• NHTSA complaints: 297 keyword-matched complaints for Buick Lucerne 2006–2011 (of 943 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-23; keywords: relay, fuse, melt, no start, fuel pump, stall). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In No start fuel pump relay service bulletin on Buick Forums, an owner posted the bulletin and explained that the rear seat frame presses on the relay. One owner's dealer did the bulletin fix for $141. Another owner of two 2008s fixed his with a used fuse block and a low-profile relay after paying about $700 on a road trip. Another suggested soldering the relay pins to the socket for a better connection.
• In 2008 Lucerne fuel pump relay trouble, an owner at about 60,000 miles found the relay scorched, and new relays kept melting within a couple of miles. Members said the fuse block needed replacing.

Quick tip

This is one of the cheapest no-start fixes out there, if you look under the back seat before buying a fuel pump.

Vehicle focus: 2006–2011 Buick Lucerne (V6 and V8). GM's bulletin is listed for all Lucernes.

Safety / mechanic note

A relay that melts plastic can start an electrical fire, and a failing relay can cause a stall. Verify with a mechanic.