2008 Buick Lucerne Fuel Pump Relay

[century61]

You do not have a short. A short would blow the fuse.
Most likely you have excessive voltage drop across the fuse relay terminal connection.
Once the original relay overheated (for whatever reason) the female terminal the relay plugs into 'enlarged' and now has poor contact. Your dropping voltage at this connection and the current is overheating the plastic.

If you cannot take the fuse relay center apart to REPLACE the female terminals you have two options:
1. Replace the fuse relay center with NEW.
2. Remote mount a new fuel pump relay OUTSIDE the center.
Obviously this second option is way outside warranty and dealer repair options. You'd need a electrical tech who really knows his stuff.

So, In essence you are saying its not actually a higher voltage that is burning up the relay but because of increased resistance at one or both of the posts coming from the supply side of the relay (were the burn is) it produces heat and actually overheats/burns the relay?

I take it you have encountered this before? Therefore the fix is probably a new fuse box under the seat.

How am I doing?

 

[century61]

I pulled the new relay out and the plastic was melted through at the "30" terminal.

I had to go back and re-read your post. Sorry, Been a long day today.

So your melt/burn is on the 30 side which is the "switch" inside the relay.

Mine seem to burn thru at the 85/86 coil side of the relay - if I have the terminology right here.

92sub's post about the situation is very interesting. Ill be thinking about that in my sleep tonite .

 

[2008Lucerne]

I agree with you 92sub, it makes sense what you are saying. Based on the appearance of my female terminal - enlarged it makes sense I no longer am making a good connection.

But what could the root cause be for overheating? I did check the fuse and it is not blown.

Century61, if your mechanic calls I would be very interested in what he says. But I may need to take mine in as well since I dont see myself replacing the relay center myself.

I noticed on your first post that your mechanic said the Fuel Pump was pulling too many volts so it was replaced. I wonder if this would have caused the original damage to your relay and relay center due to overheating??

But I am just swinging in the dark. Electrical issues are a black box to me 😕

 

[92sub]

Yes, you have high terminal resistance.

I'll try not to get into electrical theory because I'll just screw it up but let me try to explain a little more:

current = heat

So your terminal connection is poor, there is resistance there which creates current which in turn makes heat (think of your toaster) as the connection gets hotter it passes more and more current and gets hotter yet....a pretty vicous cycle.

Normally we see failures like these on blower motor switches, headlamp connectors, etc.

I'll venture a scenario (with 98% accuracy) on why your fuel pump relays have an issue and it even explains why your two relays are melting at different terminals:
1. Vehicle comes in with a legitimate no start failure.....lets say a bad fuel pump.
2. Technician starts his diagnosis by determining he has no fuel pressure.
3. He walks back to his tool box and grabs his BIG, FAT and ROUND electrical test lamp and proceeds to jamn it into your RECTANGULAR relay terminals to see whats going on.
4. Determines fuel pump is bad, repairs and sends you down the road.....along with your poor fuel pump relay connection which now acts more like a rear seat heater.

I hate to blame technicians but it's very unlikely your fuel pump relay contacts would go bad based on any other condition. There are a few relays in the same box and some of them draw quite a bit of current. While they may not operate on the same duty cycle as the FP relay I'd have to believe you'd have some other failures associated with 'large scale' corrosion/poor terminal contact vs. a localized 'human' induced reason.
Also, if this were a design flaw you'd see many, many more people complaining of the issue.

 

[century61]

Yes, you have high terminal resistance.

I'll try not to get into electrical theory because I'll just screw it up but let me try to explain a little more:

current = heat

So your terminal connection is poor, there is resistance there which creates current which in turn makes heat (think of your toaster) as the connection gets hotter it passes more and more current and gets hotter yet....a pretty vicous cycle.

Normally we see failures like these on blower motor switches, headlamp connectors, etc.

I'll venture a scenario (with 98% accuracy) on why your fuel pump relays have an issue and it even explains why your two relays are melting at different terminals:
1. Vehicle comes in with a legitimate no start failure.....lets say a bad fuel pump.
2. Technician starts his diagnosis by determining he has no fuel pressure.
3. He walks back to his tool box and grabs his BIG, FAT and ROUND electrical test lamp and proceeds to jamn it into your RECTANGULAR relay terminals to see whats going on.
4. Determines fuel pump is bad, repairs and sends you down the road.....along with your poor fuel pump relay connection which now acts more like a rear seat heater.

I hate to blame technicians but it's very unlikely your fuel pump relay contacts would go bad based on any other condition. There are a few relays in the same box and some of them draw quite a bit of current. While they may not operate on the same duty cycle as the FP relay I'd have to believe you'd have some other failures associated with 'large scale' corrosion/poor terminal contact vs. a localized 'human' induced reason.
Also, if this were a design flaw you'd see many, many more people complaining of the issue.

I want to thank you for your explanation. It certainly makes sense to me and I hope it will to my mechanic so he doesnt waste pointless time running up my bill 😉.

@2008Lucerne - I will post as soon as I hear something from my mechanic.

 

[2008Lucerne]

I pulled mine to a shop this morning. I noticed another relay with a termanal that looked like it was heated. I am going to point this out and suggest maybe I have a bad relay "rack".

Thank you all for the feedback and I will post the resolution on my car as well.

 

[century61]

Just got an email from my mechanic. He said that the fuse is of higher amps than what should be in there. This is how they kept the car running. This is why the relay is burning up. EVIDENTLY I GOT LAZY AND DIDNT CHECK EVERY DARN FUSE AND RELAY IN THE CAR WHEN I BOUGHT IT FROM A BIG DEALER 😡.

I looked over the the wiring diagram (many thanks to polarzak for this) and it shows a straight run from the relay (coil side) to the Electronic Control Module (pin 13). Iam assuming that probably the ecm is bad giving bad voltage?

Mechanic replaced pins for relay last time in. So, I will discount that as a possible problem.

Im seeing 350 bucks for a ecm for my buick.

🙁🙁🙁🙁🙁🙁🙁🙁🙁🙁 and all I wanted was a dependable car.

 

[2008Lucerne]

Sorry about this. So the root cause is a bad ECM? And it was masked with a higher amperage fuse?

Mine is still in the shop - awaiting the verdict. I think I will pass this info along as well.

Thank you! And will post a cause on mine when done.

 

[century61]

Sorry about this. So the root cause is a bad ECM? And it was masked with a higher amperage fuse?

Mine is still in the shop - awaiting the verdict. I think I will pass this info along as well.

Thank you! And will post a cause on mine when done.

Thats my thinking in all this mess. Murphy's law I suppose. The most costly part always fails. Also the fact that its a direct run from the relay to the ECM.

Just my opinion. Let me know what your mechanic says. I ll do the same.

 

[92sub]

I'm claiming bullsheet.
That relay is rated for 35 amps so an excessive draw failure would burn up the wiring LONG before the relay.
Besides, the fuse has absolutely NOTHING to do with the COIL side of the relay circuits which is the 85/86 terminal your having an issue with.
The ECM supplies 12 volts to the COIL side of the relay and the other side goes to ground. The ECM cannot 'make' more voltage than the battery supplies so therefore it can't possibly be the cause of the relay overheat.
It is my understanding that your fuse relay center cannot be taken apart so unless I'm wrong and it can, or he did something special he shouldn't have been able to replace the terminals.
Also, why did they put a larger fuse in there in the first place? Thats the first cardinal rule of electricity......don't puck with the fuses.
You need a technician who understands electricity.....the ECM is not bad, a 'too big' fuse is not causing your problem.

 

[2008Lucerne]

Ok, here's my status.

I mentioned this to my tech, and he had checked my voltage from the ECM. It was at 12V. He thought the ECM was fine. And like 92sub says it cant create volts.

He did say that the relay panel needs to be replaced. The connector in the panel on the "30" location was burned and had pulled away from the relay plug.

We are hoping it is just a bad receptacle on the panel. The fuel pump works because he was able to run it when he could get a manual connection to the terminal in the panel.

$282 for the panel plus labor - so far. They said I could shop for a panel and see if I could find a better deal.

To be continued.....

 

[century61]

@2008Lucerne - Sounds like your getting out cheap. Hopefully I do too. In fact, Im gonna forward this to my mechanic if you dont mind to cut his work time. Perhaps its the fuse panel that is bad.

@92sub - I dont know who put in the higher rated fuse. I assume the previous owner did that? I would think the dealer I bought the car from would fix the problem correctly had they known about it - Or maybe not😡.

I understand that the ecm will not "create" voltage. I was just thinking that perhaps there was a some type of bleed over from another source inside it or something wierd like that. Im really guessing as Im not the one working on it. I repair computers/laptops for a living and dont care to dig into cars. I do some work of course - as much as I can but somethings I just dont care to mess with. Anyways....

Your information is extremely helpful. I want to thank you very much for "educating" me. I guess I will just keep posting back as I get more info in. Thats all I can do at this point. I like your idea about the fuse panel and perhaps replacing that is the way this thing is gonna pan out.😕

Ok, Thanks again and I will post back when I hear more!

unimportant stuff: Finally sold my poor old 2002 century. The new owner had to do alot of work to get it up to speed. 260K miles on it!.

 

[century61]

My mechanic has a fuse panel coming in either friday or saturday. He is going to try that to see.

Here is an update to what all has been checked:

Fuel pump - ok
wiring - ok
fuel pump pressure - ok
fuel filter - ok, was replaced 2 months ago by him.
Fuel pump fuse - was a 30amp in the socket was replaced with correct one.

Im banking on the fuse panel being the problem. Just cross my fingers.

 

[sureshot]

FWIW: Batteries last longer when not exposed to engine compartment heat.

Your mechanic did good to run down the "high resistance from corrosion under the fuse panel" issue.

 

[2008Lucerne]

All right, I think we have it resolved. In my case it was a bad connector on the "30" receptacle in the fuse panel (block) under the rear seat where the fuel pump relay is placed. My mechanic replaced the fuse panel ($282 part) and checked the fuel pump to confirm it was not drawing too many amps - it checked out fine.

The car is back up and running. Though I have to admit, there is a nagging in my head as to why that plug would go bad. Was it a weak connection all along? Did something external to the fuse panel go bad?

If anything else happens I will advise but at this point - case closed.

Thanks Century61 for starting this thread. It has been helpful. Are you up and running now?

 

[century61]

My saga of the Buick fuse panel continues but should be over today (or will it??). My mechanic is replacing the fuse panel under the rear seat. This is gonna cost me 300 bucks for the panel. Now, In a day or so Iam going to post some pics of what you get for 300 bucks from buick. Your gonna all be amazed and the "quality and design" of the buick fuse panel.

All I can say right now is that when I stopped by my mechanics shop I had him "break into" the fuse panel and see what is really inside the thing. Iam amazed at what Goverment Motors calls a quality part - I can tell you that right now. It appears to me and my mechanic that the design of the panel was outsourced to some toy company!😡. As I said, I will have pics posted of it within a day or so. As soon as I get my car back. What I can tell you right now is if you have a relay overheat in it (probably just once) your going to end up replacing the whole thing! Stay tuned as soon I will be posting the pics of this wonderful design and build. I bet it cost them 1.00 to manufacturer it!

Incredible.

 

[century61]

[SOLVED]Re: 2008 Buick Lucerne Fuel Pump Relay

Ok, I promised I would post some pics of my fuse panel. Lost the cord to my camera and had to hunt a bit. Found it.

This is the top down view of my fuse panel that is under the back seat in my Lucerne. Its made from plastic. There are 3 parts to it. The top, The middle grid, and the bottom. Notice the nice burn spot on the lower right side of it?

Lets take a closer look at it:

You remove the cover by drilling out 3 -1/4 inch rivets and pull it apart. However, There are some bare wire that they use for routing the current around. Mind you, There is no insulation on these wires they depend on the plastic case to shield them I guess. Therefore, If you overheat your fuse panel you invite some rather nasty problems.

The flip side of the middle grid has more bare wires to route the current. They also depend on the plastic to shield them.

There are metal pegs that stick thru this mess and make contact to the wire harness underneath the bottom of it.

This all looks quite cheap to me for a luxury car. The new fuse panel that replaced this one cost me 300 bucks.

The real kicker is, Say someone has a problem with their fuel pump blowing fuses. Stick an over rated one in and you basically have a toaster. The inside wires are gonna heat up, burn thru the cheap plastic and do unbelievable things. .

So, My problem is, Either the previous owner or the dealer put in the wrong size fuse. I know it sounds unbelieveable but its true. A 30 amp fuse was found in it by my mechanic.

So, When ever you buy a used car you have to go thru decrapification. This is the period where you discover things done by others that cost you money to correct. 😀😀😀😀

Now the car runs great. I put on about 100 miles this last weekend on various trips and not a problem. 🙂

I think I could come up with a better fuse panel though. That thing looks sic!

Thanks also to everyone that responded to this thread. The kind words and help (especially the wiring diagram, Thank you!!).

century61

 

[92sub]

Take apart a modern fuse box in the most expensive car you can think of and I bet it looks just like this one. Why does it need to be any different?
I'm sure your upset because you paid $300 and want to see gold plating or something.....that is understandable.
But to think the DESIGN is bad because someone KNOWINGLY exceeded the design limits is pretty silly.
Lets be realistic here.....there are literally millions of these fuse panels driving around FOREVER without ever failing.
And as a side note: A larger fuse will do nothing to the circuit without a corresponding increase in current. In other words, a fuse is not a 'valve' so unless the downstream item (fuel pump) drew more current than designed the circuit never was exposed to more than allowable current.
The likeliest scenario is still: a no start condition diagnosis resulted in the probing of the fuse panel which created the poor contact and subsequent panel failure. They probably put in the wrong fuse when the relay started to fail......still didn't result in overcurrent.

 

[2008Lucerne]

Take apart a modern fuse box in the most expensive car you can think of and I bet it looks just like this one. Why does it need to be any different?
I'm sure your upset because you paid $300 and want to see gold plating or something.....that is understandable.
But to think the DESIGN is bad because someone KNOWINGLY exceeded the design limits is pretty silly.
Lets be realistic here.....there are literally millions of these fuse panels driving around FOREVER without ever failing.
And as a side note: A larger fuse will do nothing to the circuit without a corresponding increase in current. In other words, a fuse is not a 'valve' so unless the downstream item (fuel pump) drew more current than designed the circuit never was exposed to more than allowable current.
The likeliest scenario is still: a no start condition diagnosis resulted in the probing of the fuse panel which created the poor contact and subsequent panel failure. They probably put in the wrong fuse when the relay started to fail......still didn't result in overcurrent.

Interesting, because I am still not convinced the root cause of my failure has been uncovered.

1) Recently got this car so I dont have detailed history.

2) Relay failed and was replaced along with what the mechanic was a suspicious bad wire in the harness leading to the FP.

3) After about 300 miles FP Relay was melted near the 30 post. Fuse Panel was also damaged. FP was checked and found not to be drawing amps beyond spec. Replaced, panel. Has been working now for about 400 miles. I hope it is fixed but I still am not sure what caused the original failure unless it had to do with a faulty wire in the harness. Your theory about probing the panel may be what the first mechanic did and caused the second failure.

Hmmmmm. Still a mystery but so far I'm running. I need to drive for a while and then feel the relay to see if it is suspiciously hot. Maybe that will tell me if it is working ok or not?

 

[2008Lucerne]

Thought I would put up a follow up message. Since I had the fuse panel replaced and confirmed my fuel pump was not drawing too many amps (I think it was 7-8 amps) I have put over 1,200 miles on the car with no issues. I did feel the relay after driving for a while. It was hot but my mechanic said that was normal.

One last note. The mechanic said that the fuel pump had been replaced at some point. It was not the OE pump. So, there is some history to the pump.

I do think the second time I had to replace the relay was likely caused by the first mechanic probing the fuse panel and moving the connector slightly away and causing a weak connection and a melted relay. Just an opinion but I think it has merit since no other causes were found and it has worked since. So excercise caution if you have to probe the fuse panel.

Good luck.