Fuel tank over full?

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plumkrazee70

plumkrazee70

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I finally got my car on the road this past week. I got gas last night (Tanks, inc EFI tank with aftermarket guage and sender) but the pump wouldn't stay on, so the attendant had to hold it. He asked me how many gallons I wanted.

Being that I haven't driven in 8 years, I said 12, due to the guage being close to E. Drove it home, parked it.

This morning, I wanted to take it work, but after I fired it up, I saw fuel dripping from the grommet the filler neck goes in. I then opened the cap and looked down the filler neck and fuel was cresting up the filler neck.

Did I put too much in? Or do I have a faulty grommet? I was going to siphon some out after work.

70 Dart, non vented cap, vented through filler neck.
 
plumkrazee70 said:
I finally got my car on the road this past week. I got gas last night (Tanks, inc EFI tank with aftermarket guage and sender) but the pump wouldn't stay on, so the attendant had to hold it. He asked me how many gallons I wanted.

Being that I haven't driven in 8 years, I said 12, due to the guage being close to E. Drove it home, parked it.

This morning, I wanted to take it work, but after I fired it up, I saw fuel dripping from the grommet the filler neck goes in. I then opened the cap and looked down the filler neck and fuel was cresting up the filler neck.

Did I put too much in? Or do I have a faulty grommet? I was going to siphon some out after work.

70 Dart, non vented cap, vented through filler neck.
Click to expand...
If it was completely filled feul expands with heat. So if your in a warm climate maybe it was just overfill and just expanded from temp.
 
Yes fuel expands when hot.
And it will MAY damage paint if it stays wet below the fill.
I know.
But unless the tank is under some kind of excessive pressure I don't think a grommet should leak.
I've only ever had one do that.
B body with a repo neck that didn't fit right the first install .
It was under stress and I had to relive the body to make it fit without being under interference and cocked.
 
Ok, well I'll siphon some out tonight. There is no risk of paint damage as its sitting right at the grommet. It's not that warm here, not yet, anyway.

I'll also burn through this tank and re adjust the neck to the grommet. The filler is original and the grommet came from Detroit Muscle.
 
You are talking about the grommet at the TANK?? that should not leak under ANY condition. However I would be certain the vent is open and working. Excessive pressure is the only thing I can think of that "might" cause a healthy grommet to leak. Even then "it shouldn't"
 
67Dart273 said:
You are talking about the grommet at the TANK?? that should not leak under ANY condition. However I would be certain the vent is open and working. Excessive pressure is the only thing I can think of that "might" cause a healthy grommet to leak. Even then "it shouldn't"
Click to expand...

Yes, grommet where the filler neck goes in. I know the factory vent is clear, I checked when I installed. however, I did not add the tanks, inc vent that came with their kit, because they said my filler neck vent should be adequate. Maybe I should add theirs? Not sure if it can hurt.

I wonder if the filler neck isn't seated right or if my tank is not sitting right. This is the first time it's been full of fuel, only have had about 10 gallons in before (16 gallon tank)
 
The filler neck grommets will leak when they get old. They harden like steel when they are old. If the grommet is in good condition it shouldn't leak even if you fill gas up into the filler neck.
There are some better repops out now that have a second lip on them. Seem to be a much better design.
I just got one of these and it is the good one.
Mopar 71 72 73 74 GTX Challenger Cuda Road Runner Gas Fuel Tank Filler Grommet | eBay
 
Lord Sparky said:
I had a new grommet, but the filler tube had a small dent and pitting.
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My grommet leaked when I bought the car, so replaced it. Had to sand down the area that slid into the grommet because it was not smooth. I put some grease on the grommet and filler tube and shoved it in. Was a really tight fit. That cured my leak. Did verify the tank vent was intact while doing this. Sounds like your grommet is damaged, not sitting straight on the tank flange, or the filler tube needs some help. The part that goes into the grommet must be smooth and dent free to ensure a good seal.
 
I would clean it and sand it and use a good quality RTV, then let it cure for at least 3 days
 
Thanks for all the replies. I'm gonna siphon some out and burn through this tank and then drop it and take a look at the neck and the seal. I'm leaning towards it not being seated right.
 
On my Duster, once I removed the rubber trunk seal & filler tube I could clearly see the grommet. You may not need to drop the tank to check the condition and placement of the grommet.
 
Ricks70Duster340 said:
RTV turns into jelly when exposed to gas. There is one type that is fuel resistant, but I'd be hesitant to use it.
Click to expand...
Years ago I repaired a cut in a fuel tank with RTV and it was on there for YEARS. This was white GE RTV. I don't know what might have changed. I'm sure one secret is letting it set and cure fully
 
No silicone or sealer is necessary on any fuel related items.
I do question some of the rubber products being sold now.
Fuel elbows and fill hoses that show cracks after few years for example.
 
I replaced my filler neck grommet when I replaced the tank, it has leaked ever since. Even while filling up at the pump, I know when the tank is full, when fuel starts pouring out from under the car! It was a year one grommet, I'll be buying a new one elsewhere to replace it. I don't recall the tube being pitted, but I will double check it while I have it out.
 
MoparMike1974 said:
The filler neck grommets will leak when they get old. They harden like steel when they are old. If the grommet is in good condition it shouldn't leak even if you fill gas up into the filler neck.
There are some better repops out now that have a second lip on them. Seem to be a much better design.
I just got one of these and it is the good one.
Mopar 71 72 73 74 GTX Challenger Cuda Road Runner Gas Fuel Tank Filler Grommet | eBay
Click to expand...


I just bought one! We'll see if it works, thanks!
 
Its usually the damn sending unit that leaks on a new tank. They can be hard to get them to seal. I have never had a filler neck leak with a new grommet.
 
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