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Hissing sound when car is of for a few minutes.

fmontez1

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Hello all. 68 coronet 500, 318, with holley intake, holley double pumper.

Last night, I was trying to tie up some loose ends and went to Vato Zone for a gas cap, and a battery hold down. Their Battery hold down is rubber garbage. I'm going to order a proper one soon.

The cap, I'm replacing because the other day, on a slight decline hill, there was gas dripping out of my tank. That stuff is expensive! It also makes cars crispy, so I took her home and parked her, and picked up the replacement.

The rubber on the old one looked dry, but not too bad, what the heck, I changed it anyway. THe new one looked EXACTLY like the old one. Only difference was the nice new rubber, and lack of corrosion and oxidation.

I didn't drive the car yesterday, I was messing with some wiring that is giving me a headache, but I did run her for a few minutes to warm up and check the choke I was also messing with.

After that, I went under the hood to put the battery hold down tray on, and I heard a hissing coming from around my carburetor.

I read up online, and it looks like I may have a venting issue. I have a new tank, I think I just bought it off ebay, but it was brand new. Wouldn't the tank be vented? My car doesnt run warm, and I didn't even drive it, it just barely sat in my driveway running for a few minutes.
There was no whoosh when I took the cap off.

Sounded like a fluid somewhere to me, and I noticed the filter emptied.

Also I had been messing with some water temp gauge adapters, so I started squeezing lines and hoses looking for a leak in the cooling, but none. Really took our relationship to another level the way I was squeezing her hoses and pushing the fluids around. haha

Anyway, no water leak.

So wouldn't a new tank be vented?

I read on here somewhere about people drilling a 1/8 hole in the cap, wouldn't gas shoot out under acceleration? That doesn't sound like an option, especially with my exhaust coming all the way out back. Heck no.

Anyway, I'm rambling at this point. I do have a holley directly on the intake, so I am going to throw a spacer on there.

Just frustrating trying to tier up these "loose ends" and it turns out there is some other bizarre thing happening. This is a hell of a hobby we have here!
 
I'll bet you got a non-vented cap and your fuel pump created a vacuum in your tank. The hissing you heard was probably air being sucked back into the tank which would explain a dry filter. Check your tank to make sure it isn't collapsed now.
 
I'll bet you got a non-vented cap and your fuel pump created a vacuum in your tank. The hissing you heard was probably air being sucked back into the tank which would explain a dry filter. Check your tank to make sure it isn't collapsed now.


I left it open this morning fearing the same. I didn't get many responses here, and I need a new sender anyway, so I'm going to check if that tank is vented or not. Its brand new, I would figure it was, but now not so sure.

I actually left the tank open today, because with the summer sun, I was more afraid of pressure building, and forcing gas into my engine without it running. I'm still breaking her in, so these, I suppose, are some of the gremlins to look out for.
 
Your quote:
"I read up online, and it looks like I may have a venting issue. I have a new tank, I think I just bought it off ebay, but it was brand new. Wouldn't the tank be vented? My car doesnt run warm, and I didn't even drive it, it just barely sat in my driveway running for a few minutes.
There was no whoosh when I took the cap off."

You installed the tank so you should know if it is a vented tank.
More on the "Tank Vent" issue.
There should be 2 lines coming from your fuel tank.
1. The 3/8" line to the fuel pump (5/16" for Hemi cars)
2. The 3/8" line back to a cannister OR tank, depending when and where your car was made.


NOTE:
From Classic Industries

[1968-70 B-BODY FUEL TANK VENT LINES, ORIGINAL MATERIAL
Correct replacement fuel tank vent tubes which extend from the fuel tank across the trunk. These lines are produced in the original material for a correct look. Each line is designed to OE specifications and is guaranteed to fit each specific application perfectly! Replacing your vent lines can improve your fuel system while retaining originality.
For 1968-70 B-body models, except Charger.]

Also check Vans Gas tanks for the diagram of your set-up



Question is: "do you have the 2 lines?"

fmontez1; Research "on-line" AND on this FORUM the correct fuel line set-up from tank to fuel pump.

- - - Updated - - -

On "TOP" of page to the right Just type in: Fuel tank vent lines....
Then search a couple of "posts" down untill you see Richard Craniumns post dated: 5-01-2013

NOTE: The "Search option" is a viable tool on the Forum.
 
Your quote:
"I read up online, and it looks like I may have a venting issue. I have a new tank, I think I just bought it off ebay, but it was brand new. Wouldn't the tank be vented? My car doesnt run warm, and I didn't even drive it, it just barely sat in my driveway running for a few minutes.
There was no whoosh when I took the cap off."

You installed the tank so you should know if it is a vented tank.
More on the "Tank Vent" issue.
There should be 2 lines coming from your fuel tank.
1. The 3/8" line to the fuel pump (5/16" for Hemi cars)
2. The 3/8" line back to a cannister OR tank, depending when and where your car was made.


NOTE:
From Classic Industries

[1968-70 B-BODY FUEL TANK VENT LINES, ORIGINAL MATERIAL
Correct replacement fuel tank vent tubes which extend from the fuel tank across the trunk. These lines are produced in the original material for a correct look. Each line is designed to OE specifications and is guaranteed to fit each specific application perfectly! Replacing your vent lines can improve your fuel system while retaining originality.
For 1968-70 B-body models, except Charger.]

Also check Vans Gas tanks for the diagram of your set-up



Question is: "do you have the 2 lines?"

fmontez1; Research "on-line" AND on this FORUM the correct fuel line set-up from tank to fuel pump.

Your clip from classic industries was all I really needed, thank you. I'll check how it was installed.
I didn't install the tank myself. Thats why I said I was going to drop the tank, and check the venting.

I have been researching here, I searched for HISS and only got about 30 articles. If you could point me to a more specific one, maybe something showing the vent lines I'm looking for, that would be awesome.

I've also been looking online at other forums.

The idea about drilling a 1/8 inch hole, actually was from either this site, or FABO, and that didn't sit right with me, that's why I asked.

So, again, thanks for all the info. Like I also said, I'll be dropping the tank soon, and I'll double check then.
Appreciate it!
 
Went back under my car today.

Also was reading a few threads here online, this thread had the right shop manual pages in it. Had some good info on the fuel lines, vent lines.

I went underneath and looked, saw the tube coming out of the tank, FIRST PIC

Followed that line into my trunk. ANOTHER PIC

So I'm satisfied that my tank is vented, and the fuel line out looks and works very well. However in the FBBO Link above, the Shop Manual pics (CLICK HERE FOR PIC) shown look like there are two hoses on the vent side. I only have one, and what felt like a cap where the second one would be. Should I run a line from there (The non vent side, the one that doesn't run trough the trunk) to somewhere? I think I'm over thinking this. It seems to work, and as far as my hissing sound, I figured out what it was. I had a loose radiator hose.

I just associated it with the Fuel tank, cause I only ever heard it a few minutes right after installing a new gas cap.


Well at least I went down there and took a good look around, and everything seems normal.

One more question though, and I couldn't find this anywhere. . . What does the vent line, after the big U, where does it VENT to? What's a safe location for a vent?
 
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