Relay failure was a common issue, the problem is cause by a fuel pump drawing excess amps causing the relay to get hot and melt the relay/fuse block. Replace the in tank fuel pump and fuse block/relay center assembly.

 

But that's the problem. I already replaced the fuel pump and fuse box but the relay pump keeps melting. What should I do if it keeps melting after replaced those part?

 

Sounds like some wires are damaged from the previous issues. Check all wiring at the fuse block and at the fuel pump. A short to ground will draw excessive amps causing an over heat and melting condition.

 

Do you regularly carry passengers in the rear seat? If so, a heavy passenger (or regular passenger occupancy in the left rear seat) can put pressure on the lid of the fuse box and push the relay sideways. There were more incidents of this kind with the sister Buick Lucerne platform, but the DTS experienced some of the same issues.

It's a long shot, but GM did have a technical bulletin out on that same issue concerning the Lucerne.

There is a Lucerne repair video on YouTube that addresses this issue --

 

I found out the real problem. Apparently, it wasn't my fuel pump relay. My car was stalling out due to my crankshaft position sensor. Thank you everyone for all of your help.

 

Hi, so my dt’s is doing the Exact same thing. I Changed the pump and relay. I don’t think the fuse box is ruined yet. Anyways, you said that it ended up being your crankshaft sensor. Can you explain to me, why or how that’s effecting the relay. Or is it not?

 

Kande, Welcome to CF !!!! What year DTS?

What exactly are your stalling symptoms? During warmup, driving, coastdown, slow turns - when?

A CKP (CranKshaft Position sensor) failure causes random stalls at slow speeds with immediate restart.

Have the car scanned at any parts store and post the found diagnostic trouble codes and their definitions here.

Use this link to better define codes -

OBDII diagnostics. Trouble codes description for GM

OBDII/EOBD diagnostic code definition. More than 18000 codes for all autos. Trouble codes description for GM

obdii.pro

 

Hi, I’m so glad to have found this forum. I love my 2008 Cadillac DTS v8. I’m not quite ready to give this guy up. I moved to Pensacola Florida a few months back and everyone I’ve met here act like Cadillacs are a different breed of cars. They always comment, good luck finding a mechanic that works on Cadillacs. Which is odd to me. I think I’m just talking to wrong breed of people. Lol. I mean it’s a Cadillac for heck sakes!
Anyways my pump went out. That’s when I discover the relay was burnt out. Bought a new relay tried it. Nothing happened. I think the second relay blew due to the pump being out. So I went and replaced the pump. Nothing happen. Until I put a new relay in. Started right up. Now the relays keep burning up. So I’m guessing my box thingy is toast. I didn’t think it was at first because, there was no signs of melting or anything. Now though, I realize if the relay isn’t angle just right and has no pressure on it from the seat, it last longer. So I need to order that what ever it’s called box. Lol.

 

Check where the rear seat clips in. The metal requires to to trimmed so it is not touching the fuse box.

 

Just wanted to give an update. I changed out the fuel pump. Also replace the rear fuse box. Which is now a discontinued. so it took a min to find one. It fired right up! Yay.
That’s was way exciting.
Although a new problem has started. Now I’m getting system needs maintenance alerts. For things like traction control, brake assistance and I can’t remember the other thing.

 

I have 2008 DTS lux 2 with 90,000 miles doing same thing. Relays burned up and box melted to. So i installed a new Ac Delco fuel pump new fuse/relay box and new relay. that was a year ago. Now here we go again. same problem. Nobody rides in back seat either. Im ok shade tree mechanic but stumped. Please help!

 

I Disagree. From my experience with the 2008 DTS is the Fuse / Relay module itself. I did a simple bus secure bypass on mine and never had an issue again. When I hear of anyone with this problem I give them the info so they can perform the operation.

Can I get that info?

 

Can I get that info? 414-403-5334

Hi, the person you're looking for joined 17 days ago and it doesn't look like he's signed on again since. But who knows, maybe you'll get lucky! I'm not sure it's a great idea posting your phone number on here. Not really sure why but I've seen people frown on it. You might be able to find what you're looking for by searching the archives. I've seen a lot written on this topic. Good luck!

 

One of the reasons people "frown" upon posting personal contact info is that this huge worldwide site with over 350,000 "members" is infested with spammer and scammer scum that is just waiting to reel in a big fish. Happens every day.

Ever seen the typical "E-mail my cousin Joe at www.scammer.love.com - he has one he'll sell you cheap !" posts? BINGO!

Best to use our "Conversations" (Private Message - PM) function.

 

.......... and FWIW, many of the replacement fuel pump/level sender assemblies come with a larger electrical connector and pigtail that gets spliced into the existing harness. Less overall electrical resistance. Remember - that pump runs any time the engine is ON.

Note the flat 4-blade connector as opposed to the early square 4-pin type.

More Information for DELPHI FG0347

(DELPHI - an original and huge parts/development center for GM. DELPHI and Lord were the developers/licensing entity for every MRC system on earth.)

 

2009 DTS fuel pump relay burnt up, melted a bit of the fuse box. My wife was traveling (she couldn't go Thursday the 12th, had to be Friday the 13th), anyway got a new relay and drove car 2.5 hours home. Current draw on pump was 10A. Put in new fuse box and Delphi fuel pump (per posting on Rockauto it draws 10A, with a note of (68) next to it (is that farenheight?). Tested current on new pump, it's at 12.5 and it's about 40F out today if that makes a difference. 20A circuit but the wiring is so tiny, don't know how they get away with that...or do they.

The new fuse box came with the shorter relay and I did notice the first replacement tall relay I got was a new part number.

People rarely sit in the back seat, no signs of contact with seat to old fuse box.

So, is 12.5A too high and could this whole issue be due to an undersized OEM relay? Car has 108,000 miles on it.

 

2009 DTS fuel pump relay burnt up, melted a bit of the fuse box. My wife was traveling (she couldn't go Thursday the 12th, had to be Friday the 13th), anyway got a new relay and drove car 2.5 hours home. Current draw on pump was 10A. Put in new fuse box and Delphi fuel pump (per posting on Rockauto it draws 10A, with a note of (68) next to it (is that farenheight?). Tested current on new pump, it's at 12.5 and it's about 40F out today if that makes a difference. 20A circuit but the wiring is so tiny, don't know how they get away with that...or do they.

The new fuse box came with the shorter relay and I did notice the first replacement tall relay I got was a new part number.

People rarely sit in the back seat, no signs of contact with seat to old fuse box.

So, is 12.5A too high and could this whole issue be due to an undersized OEM relay? Car has 108,000 miles on it.

i moved my relay outside the fuse box. Relays can get warm. Once the 12v pin for the relay gets warm (due to confined location and cramped conditions) enough it deforms and is no longer a solid connection. Bad connection equals increased heat at connection. And this continues until crap chars.

you can see the hole next to the 10 amp fuse wrecked. Take a wire and go directly off the main 12v input to the fuse panel and directly to your relay 12v input pin. Make pig tails and go off your relay to their respective holes on the fuse panel. Secure relay outside the box (cut a slot in plastic cover for pigtail wires to fit through)

yes..I used speaker wire😂

 

This^ before I found this thread I replaced my fuel pump, 09 Cadillac DTS, thinking it was what kept burning up the relay (even though I had the exact same scorch marks on the exact same terminal as your pic) and was STILL frying relays. And you could tell pretty well immediately because if the car was on for even a couple minutes the relay would be fire-hot. So I found this..wired her up just like you did in the picture and voila. Had it running in the driveway for a couple hours this morning and not only did it not fry the relay but it was barely warm. You sir are a genius. My next step was replacing the entire fuse box but we have no one that works on Cadillacs in my area so needless to say I am very grateful for you posting this as it saved me hundreds of not thousands of dollars on repair or just buying a new vehicle cause although I love my DTS it definitely has taken some tlc to keep her going. Thanks again and anyone else have a terminal that looks like this the wiring was gravy cost me $20 in spades and wire etc.. and only took maybe 30 minutes.

 

Thank you

I think I’ll go with your plan

any thoughts on the new Delphi pump pulling more amps than it is rated to or the old one did?

thanks again

 

And this new pump seems loud

can anyone else hear theirs easily from inside the car? Don’t remember hearing the old one but maybe never noticed it

thanks

 

My DELPHI replacement pump assembly (2014) is dead silent (well, maybe a barely audible hummmmmm) except when the fuel level is very low. BAD idea to run these cars with less than 1/4 tank habitually.

Maybe some un(sound)insulated pump part is vibrating against the tank ?

 

Thanks

it seemed loud before I buttoned it up

coupled with the higher amp draw I think bad pump

last summer I got a bad Delphi for another vehicle

case was cracked

appreciate the help

 

Replacement pump on its way

 

2nd new pump quieter but still pulling 12.5 amps

guess it is what it is

 

Forgot to zero out meter

11.7 amps

 

Good read. I am having the same issue now. Waiting for my pump. They said it will be here tomorrow. I put a new relay in it that lasted 1 start and move to a different parking spot. Started yesterday morning to warm up and it did start, but I went out and tried to start it again and it didn't. Haven't even looked at it, I was pissed. I think I might isolate the relay like the post above.

 

I feel for you. Very frustrating. I’m a farm kid turned engineer, worked for Caterpillar for many years, and this system is totally under designed. After my beautiful but unreliable 94’ Concours I swore off Cadillacs but in 2016 the deal on this one was too good to pass and I needed a car. 2009 DTS, 18,000 miles for $5500 from an elderly family friend who had to give up driving.

Anyway, checked my 2nd new pump (first replacement was louder than this one and drawing 12.5A) recently and it’s still pulling 12A, the rating is 10. I was hoping the pump would “break in” The original pump which in the end was not the issue only pulled 10A. Used Delphi replacements. Delphi has quality issues but everything I read says they are the ones to use.

There was a thread on putting the relay outside the fuse box which would likely help a lot, I just have not done it yet. Guess I’m a slow learner…and too busy to keep fussing with this thing.

Relay is not getting hot. My new fuse box came with the shorter and I hope heavier duty relay.

I have no faith in this car RE taking a road trip. Just changed the belts at 110,000 miles. Shouldn’t have to raise the engine to change a belt. Water pump belt was starting to separate along the grooves.

Engine starting to leak more oil. It was resealed before I got it at 12,000 miles. Hoping it’s valve covers but for now oil is cheaper than working on it. I would really like to get rid of this car and get another RAM truck but the numbers don’t shake out right now; the car is not worth much; $2500 I think.

Before 60k miles front wheel bearings, rear shocks, top strut plate on one side etc. My 1997 Concorde at 297,000 miles, it had a few problems along the way but never put a wheel bearing in it.

Seems GM puts it cheapest parts into it’s flagship line.

Shouldn’t say this to a group of Cadillac fans, especially since I don’t want to get barred from the forum and I’m a huge fan of the 1976 and older cars, but this is my last Caddy.

So if anyone knows of someone who wants to overpay for what is still a great looking DTS let me know, we should talk.

 

Water pump belt was starting to separate along the grooves.

Did you change the water pump drive belt tensioner pulley? Common failure part at ~75,000 miles. No need to change the entire tensioner.

 

I actually changed both tensioners and belts

didn’t have a wrench that I could get idler pulley off

it spins great so I left it

appreciate the info

 

"spins great" may be misleading, as a "good" pulley bearing with sufficient grease will NOT spin - it will be "sticky" and viscous when turned by hand.

New tensioner = new pulley - Gates/DAYCO

 

That was the first thing I did on mine, was replace the tensioner pulley. Don't feel like doing a water pump anytime soon.

 

I used to be a big fan of Dayco

they’ve become junk

Been having good luck with Gates

mechanic friends agree

 

Probably suffering from poor quality Chinese fever.