Fuel pump relay

[Rigo1G]

My fuel pump relay has burnt out twice in less then a week. What could be causing it to do that?

 

[DrivenDaily]

Too much current being drawn by the pump or some other issue.

 

[2007LucerneCXL]

2008 and up Buick Lucerne's have a problem with the rear seat fuse box with the fuel pump relay. Replacement of the fusebox or modified the the relay location as a possible repair which is dependent on how much damage is done to the box.

Lots of posts on the site in the Lucerne forum.

2008 Buick Lucerne Fuel Pump Relay Issue

hi all, i purchased my 2008 buick lucerne two summers ago with a little under 60k miles on it, its currently at 78k. haven’t had many issues with it at all until recently, first time was when my car wouldn’t start as the battery wasn’t getting enough power, so the alternator was replaced. a few...

buickforums.com

 

[Movedon]

Hi,

First post here, interesting to see this issue.

I had the same problem.

There was a technical service bulletin about this for Lucerne and Cadillac DTS.

The problem/cause is probably the back seat. Not to say it couldn't be a pump going bad, or a bad ground, but this is the one that I had after all the research.

There is a metal tab (usually one causes it but there are two) under the seat that's part of the seat frame that has to be cut off, described in GM Technical Bulletin SB-10108617-9340. There are photos in the bulletin indicating how to do the fix. (Attached mine also)

GM put a relay in that had a higher (tall) profile, which meant the cover rubbed on it.

You can get an idea very easily just by lifting the back seat lower cushion and look to see if those tabs are there. If so, that's likely the cause of the problem.

What happens is that this tab presses against the fuse block cover right by the fuel pump relay - which wiggles the fuel pump relay causing the contacts to loosen and short over time - resulting in burning out the relay.

The good news is that this is probably the fix if the tabs were not cut off by a dealer when the bulletin was released. There was actually a secret warranty up until about 2020.

The bad news is that the contacts inside the block (the female part) get hot and expand and oxidize meaning you get poor contact, then even putting in a new relay will result in it moving around with the heat from resistance and being loose, shorting, and popping the relay again.

In mine the final fix was to modify the seat, and replace the fuse block. I did that about a year ago and have had no further problems at all with it.

I did try messing around trying to clean the contacts inside as well as I could and shim the contacts with small brass strips but no use.

There was one video I found where the person went to great lengths to disassemble the fuse block and replace the contacts inside (double ended females in a two-part block assembly).

I can't guess whether that worked for him long-term, but I decided to just replace it since the block itself scorched with two repeated burnups of the relays.

I'm attaching a photo of the block and the current GM OEM part number. There are still some around, pricy but worth it.

I tried attaching the bulletin pdf, but the forum won't allow a 4mb upload.

Here is a link to the bulletin on the NHTSA website

https://static.nhtsa.gov/odi/tsbs/2017/SB-10108617-9340.pdf

It covers 2008 - 2011 Lucerne and Cadillac DTS

I'd shop around for prices but here is on source:

84446208 - GM Parts Giant

www.gmpartsgiant.com

It took about 45 minutes to Re & Re - I did it myself.

It was straight forward.

Do the seat modification if it hasn't been done and there is no other cause to burn out relays (bad pump etc.)

1. Disconnect battery
2. Disconnect fuse block battery cable
3. Remove old block
4. Compare old block and new block and remove un-needed/unused fuses and relays from the new one (the new one is fully loaded so you don't have to transfer old/used ones into a new block)
5. Be sure to clean the contact surface of the power/battery cable to the block.
6. For good measure I removed the ground/negative cable where it bolts to the body and cleaned both to make sure I had good ground.
7. Clean both battery posts/pads, and terminals.
8. Install the new block.
9. Put it back together, connect the battery (+Positive cable first, then -Negative ground) and you should be good to go.

If that's not it - good luck finding the cause.

 

[JLF_1977]

I had this problem with mine. There is a revised fuse box that I swapped in...but my original problem took out the fuel pump, too. I did not cut the tabs on mine...the back seat is never used.