Hey guys, I have a problem. A few months ago my father and I replaced the fuel pump in my Camaro. Since then there has been this horrible croaking sound coming from the rear of the car (I'm assuming from the gas tank). The best way to describe it is: there is a giant toad in my back seat, and it is slowly dying. It only makes that noise when...

a)I drive the car for about twenty minutes, and then prime the pump after a few minutes of sitting. The pump primes normally, then makes this sound for a few seconds.

b) I drive the car for a little while, turn it off, wait a few minutes, and then it starts making that noise all on its own for about 10-20 seconds.


I've also noticed that now my gas cap releases pressure when I open it, which it didn't do before. So is there just too much pressure in the tank, and that's whats causing the noise? I'm at a loss here, and would really like to fix this. Thanks y'all.

 

im not aware of the sound myself, but this has come up many times.. there is some relief valve under there.. i think mine is hooked up near where the brake & fuel lines run down the body.. giant dying toad, thats a good one

 

My guess is when the tank was put back in the vent hose got pinched. Probally have to drop the tank low enough to move the hose over to where the grove is for the line.

 

The gas tank is supposed to hold pressure. That's normal.

Look under the car, just in front of the rear axle, just inside of the front LCA mount point. You'll see a gray plastic thing with a hose going to it, often described as a miniature UFO. That's what makes the noise.

I've often described as something blowing its nose; and others describe it as sounding like a goose that's dying. Sounds all like about the same thing.

Just replace it. AFAIK it's a dealer-only part. Its official name is something like "fuel tank pressure relief valve". It's about $30 or so.

 

I know exactly what part you're talking about, I saw it when we swapped the pump.

I knew it was going to be something plain and simple, but I'm just not very familiar with the fuel system. Well I'll give that a try and let you all know how it goes. Thanks a lot.

 

Okay so I replaced the part pictured below. It was connected to the gas tank via a rubber hose. Didn't fix anything... So that's $37 down the drain. Any other ideas? Could it be the fuel pump itself making the noise? Because all we replaced was the pump, pump screen, and the gas tank seal. Thanks again for all the input.

 

Bummer dude....

So when you have created the conditions under which it does it, and then laid up under the car listening and waiting for it to do it, where did you hear the noise coming from?

 

Well it isn't a consistent thing. So it's hard to get under there to listen for it since I never really know if it's going to do it or not. But now that I think about it, the sound does have sort of a metal echo to it. As if it's coming from inside the gas tank. Does that help at all?

 

did you replace the rubber isolater on the bottom of the pump where the strainer is? also earlier cars had a isolator boot around the fuel pump to quiet the .... check to make sure fuel lines are secured to the lip of the fuel tank. they vibrate like hell when they are loose. Check to make sure fuel tank is seated correctly and rubber isolator on the fuel tank straps are in place.

Check tin shields that were removed to make sure they are bolted in correctly ... pull vent line to the charcoal canister and see if that stops the problem ...

 

I don't quite recall if we replaced the rubber boot or not. We probably did. And if not, there's no way in hell I'm dropping that tank again unless it's necessary. And I'm pretty sure everything is on there tight. I'll give the charcoal canister thing a try though. Thanks.

 

you know I also recall the pump itself has a check valve internally to keep pressure on the feed line to fuel rails. Maybe thats all your hearing is it's not functioning right and is what your hearing is fuel being forced back into the tank is all ... its no biggy just means takes longer to prime is all

 

And another thing, it often makes the noise after the car has been shut off and sitting for a few minutes. So I'm pretty sure it doesn't have anything to do with the sraps. And the noise gets louder, quieter, and gradually fades out. Which is why I'm leaning towards a pressure issue.
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That could be it. It does make the noise after I prime it sometimes, so that would explain that. So it may just be a faulty fuel pump? Does AC Delco offer a warranty or anything on these?

 

probably ... loosen the fuel cap to and see if it makes the noise as well.

hook up a pressure gauge and see if it bleeds down line pressure quikly

maybe its this tank pressure and air is trying to bleed off anywhere it can LOL

Don't blame you on not wanting to drop the tank again ... I cut the hole in the floor thing on mine. So it's easy to change the pump now LOL ... After droping a tank 3 times in a week it makes one think of an easier way to do it LOL.

 

I feel its gunna be something to deal with the priming of the pump, as when a pump primes you get that little vibrating noise....well this seems to be hightened on his. So check pump and let us know....

I will in the future be getting their 4th gen kit and making it work in the 3rg gen...as I have heard..only the filler neck needs to be modded. www.NASTYPERFORMANCE.com

 

Well the pump makes the normal humming noise. But sometimes it makes the normal humming noise, and then makes this groan of death. I'll investigate further in a few hours.

 

Posting on the Internet and getting a bunch of "maybe it's this, maybe it's that" isn't going to get you anywhere. We've already had you change out the usual suspect; that didn't fix it, which is a surprise, really; so now it's time for a little more direct investigation.

Futzing around with the gas cap isn't the answer. There's hundreds of millions of cars on the road with that don't make the noise, and don't require futzing with the gas cap. Yours didn't used to require futzing with the gas cap. If it does now, but the gas cap isn't broken, then there's something else wrong.

Instinct tells me, it won't be the pump, won't involve cutting holes inthe floor, won't involve the gas cap, won't involve the straps.

You know what you can do that makes the car make the noise.

Just make it do it, and go listen. You might have to try it a couple of times (drive the car or idle it for a while or whatever works best, maybe put it up on ramps so it's easy on yourself, shut it off, lay on the ground under it, wait); but sooner or later, it'll do it, and you'll be able to find it.

That's how I found it in my car. We didn't even have the Internet back then; Al Gore hadn't invented it yet.

 

Okay, I took it for a spin and parked it in the garage. It started to make the noise about a minute or two after I had shut it off. Once it started I loosened the gas cap until it hissed, and let it vent until I couldn't hear it hissing anymore. That didn't stop the noise at all.

So can we rule out a pressure problem?

 

Probably so...

What part of the car was it coming from? Left? Right? Top? Bottom? Front? Rear? Inside? Outside?

 

Okay, took it for another lap around the golf course and got underneath it this time. I noticed that the fuel lines coming out of the tank vibrate in sync with the noise, which I suppose points more in the direction of an actual fuel pump problem.

And I even have a little recording for you guys now! Sometimes the tempo of the creak is a lot faster. Hope it helps.

http://www.youtube.com/watch?v=mkzJFhPScB0

*EDIT*
Also, I can't really distinguish where exactly the noise is coming from. But so far it seems to be coming from inside the tank.

 

mine kinda sounds like that but its only when i have the fuse for my hatch in, it sounds like the fuel pump is dying buts its the hatch mechanical latch thingy yea that thing lol