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Gas is leaking from rubber grommet #2880798
01/27/21 09:59 AM
01/27/21 09:59 AM
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KZ4406 Offline OP
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After a 4.5 yr complete OE restoration on a 1970 Challenger RT/SE 440-6, I discovered that if I fill the gas tank to full, gas will leak from the rubber grommet that connects the filler tube to the gas tank until the level of the gas falls below the rubber grommet.

Question: Can the rubber grommet be replaced w/o dropping the gas tank? I.e. can the filler tube be pulled out of the grommet with the tank in place?

The car is immaculate, Gold Certified, worried about scratching newly coated OE parts.

Thanks for any help you can provide.


Last edited by KZ4406; 01/27/21 10:02 AM.
Re: Gas is leaking from rubber grommet [Re: KZ4406] #2880811
01/27/21 10:42 AM
01/27/21 10:42 AM
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BDW Offline
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No, and no,
You'll need to drop the tank to remove the filler tube.

Re: Gas is leaking from rubber grommet [Re: BDW] #2880819
01/27/21 11:01 AM
01/27/21 11:01 AM
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KZ4406 Offline OP
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Thanks, I was afraid of that

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2880888
01/27/21 01:43 PM
01/27/21 01:43 PM
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moparx Offline
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where was the neck grommet purchased from ?
if it was NOS, was it nice and soft when it was installed ?
at times, 50yr old NOS rubber parts aren't usable in certain applications.
beer

Re: Gas is leaking from rubber grommet [Re: moparx] #2881100
01/27/21 09:26 PM
01/27/21 09:26 PM
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Originally Posted by moparx
where was the neck grommet purchased from ?
if it was NOS, was it nice and soft when it was installed ?
at times, 50yr old NOS rubber parts aren't usable in certain applications.
beer


Could also be an ethanol culprit wink

Re: Gas is leaking from rubber grommet [Re: TJP] #2881134
01/27/21 11:14 PM
01/27/21 11:14 PM
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Honestly, I would trust a NOS one before i would trust some China junk.

Re: Gas is leaking from rubber grommet [Re: mopars4ever] #2881135
01/27/21 11:35 PM
01/27/21 11:35 PM
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I had that same thing happen after I replaced the fuel tank on my ‘71 Challenger a while back. After a few weeks it stopped, I don’t know what happened but maybe the grommet swelled a little from the fuel and that made it seal?

Re: Gas is leaking from rubber grommet [Re: Mastershake340] #2881366
01/28/21 04:18 PM
01/28/21 04:18 PM
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KZ4406 Offline OP
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The rubber grommet was a new one most likely purchased from Detroit Muscle Technologies or some other vendor that had similar part. I only used OE for most of the parts I needed but on something like that grommet, I don't think I even considered looking for an OE, and yes, 50 yr old rubber would make me worry

I only filled the gas tank up that once, using unleaded premium no ethanol gas, maybe the rubber has seated or swelled, but I am not willing to fill the tank up to find out. I cannot leave that car anywhere but in the covered garage it is in now.

I was thinking that maybe when the guy who restored my car put the filler tube and gas tank together that maybe the grommet was "pinched" or maybe slightly cut so that it does not seat like it should

I hate to pay someone to drop the tank but know no other way to find out if the grommet is compromised

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2881392
01/28/21 04:40 PM
01/28/21 04:40 PM
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I just put in a new tank and replaced the grommet at the same time.
Your best bet is to also remove the valance, tough to do with that in place.

Last edited by BDW; 01/28/21 04:40 PM.
Re: Gas is leaking from rubber grommet [Re: BDW] #2882076
01/30/21 03:32 PM
01/30/21 03:32 PM
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Thanks for all of the replies, I will be having a top-notch restoration shop replace the rubber grommet. I hope that is the culprit but I don't see how it could be anything else since the tank, rubber grommet and filler tube are all new

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2882362
01/31/21 12:42 PM
01/31/21 12:42 PM
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moparx Offline
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i like to use a little dish soap or creme hand cleaner [without the grit] on the filler tube when installing the tube to the tank.
it seems to not hurt anything, and is easy to clean up afterward, plus it seems to protect the grommet from nicks.
i also use a dab of that stuff on the tank lip for the same reason[s].
beer

Re: Gas is leaking from rubber grommet [Re: moparx] #2937841
06/28/21 10:00 PM
06/28/21 10:00 PM
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Rubber grommet was replaced.

I filled the gas tank to the max. On level ground, gas tank was not leaking. I drove the car 5 miles from gas station to my house, backed the car up the driveway, the driveway has a decent decline but nothing drastic. No leaks, but after 5-10 mins, I saw gas dripping on to the ground, drip was coming from the left side of the Dana housing as you look at the car from the rear. I drove the car immediately back to the shop but their floors are level, so of course, no leaking.

Since the rubber grommet is taken away as a possible culprit, that leaves 2 other possibilities that I know of. The sending unit rubber gasket and/or sealing ring, or one of the seams on the gas tank is bad. Both are brand new when put on the car 4 yrs ago. Car is OE Gold certified so every piece on the car is new, OE, etc.

Does not make sense to me, if there's is a leak on the decline why wouldn't the fuel leak on level ground? The gas tank is very full.

Also, with full tank, gas gauge reads full at idle but when driving will drop to 1/2 tank, does that sound like a bad ground connection?

I would love to here opinions/suggestions/comments

Thanks

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2937845
06/28/21 10:09 PM
06/28/21 10:09 PM
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MYRTLE BEACH SOUTH CAROLINA
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Originally Posted by KZ4406
Rubber grommet was replaced.

I filled the gas tank to the max. On level ground, gas tank was not leaking. I drove the car 5 miles from gas station to my house, backed the car up the driveway, the driveway has a decent decline but nothing drastic. No leaks, but after 5-10 mins, I saw gas dripping on to the ground, drip was coming from the left side of the Dana housing as you look at the car from the rear. I drove the car immediately back to the shop but their floors are level, so of course, no leaking.

Since the rubber grommet is taken away as a possible culprit, that leaves 2 other possibilities that I know of. The sending unit rubber gasket and/or sealing ring, or one of the seams on the gas tank is bad. Both are brand new when put on the car 4 yrs ago. Car is OE Gold certified so every piece on the car is new, OE, etc.

Does not make sense to me, if there's is a leak on the decline why wouldn't the fuel leak on level ground? The gas tank is very full.

Also, with full tank, gas gauge reads full at idle but when driving will drop to 1/2 tank, does that sound like a bad ground connection?

I would love to here opinions/suggestions/comments

Thanks
a build up of vapor pushing fuel out after moving the car? maybe past a clamp or other opening?

Re: Gas is leaking from rubber grommet [Re: ek3] #2937855
06/28/21 11:02 PM
06/28/21 11:02 PM
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Freeport IL USA
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If the gas gauge is giving you strange readings, it is possible the sending unit mat also have an issue with the seal between the mounting flange and the fuel outlet tube. If the tank is not level, the lowest side will have gas higher up on the tank then there would be if the tank was sitting level. It may be possible gas is reaching to a vent when the car is not sitting level.

One cure for this is to stop putting gas into the tank when it first clicks off. The gas coming out of the underground storage tank at the gas station is cooler, and gas expands as it warms up. If you fill it to the brim at the gas station, the gas has to go someplace when it warms up and expands, anywhere between 5 and 15 minutes later. Gas, being an expanding liquid, will force its way out of anyplace it can. Gene

Re: Gas is leaking from rubber grommet [Re: poorboy] #2937888
06/29/21 06:58 AM
06/29/21 06:58 AM
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Ive had my. gas tank up and down a dozen times in my quest to get the sending unit to read correctly and so what I know is the filler neck grommet you have tube careful that it doesn't get damaged or doesn't seat properly
As.far as the sending unit a good rubber gasket is needed but not all locking rings are the same thickness.....Better quality locking rings are slightly thicker steel and this puts more pressure on the rubber seal
Im sorry cant remember were got my locking ring, but I know the cheap China ones are thinner material . That grounding strap also has to be tight and clean, a good ground is the first. thing to check

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2937912
06/29/21 09:20 AM
06/29/21 09:20 AM
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Since it's all OE Gold Certified, quit driving and putting gas in it. Just roll it out of the trailer, push it to it spot in the car show and park it, so everything remains pristine. No more gas and no more leaks. If you drive it, it goes from being a pristine number 1 car to a number two car in the first few miles. I've seen several super high end restored Mopars that have never been driven, and they are amazing, but useless in my book.


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
Re: Gas is leaking from rubber grommet [Re: Kippy] #2937932
06/29/21 10:49 AM
06/29/21 10:49 AM
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The retainer rings are designed so they can be tighten up to squeeze the sealing rubber gasket tighter by driving the sealing ring further, tighter, deeper into the tank sealing taper that it slides into scope wrench twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Gas is leaking from rubber grommet [Re: Cab_Burge] #2938015
06/29/21 01:52 PM
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Thanks for all of your replies.

Today I received a call from the shop, they found the answer.

They put the rear of the car on racing ramps to simulate the gas leaking condition I was experiencing and they topped off the gas tank. But there was NO LEAK!

So they started to hand touch each item down there and lo and behold, one of the rubber hose clamps was loose. If the car was at just the right position the clamp would slip and leak fuel.

They put on another correct clamp for that car and got around the issue of getting the crimping tool in there by popping one of the rubber plugs in the trunk lid one of which was exactly over the area.

Voila! No more leak.

Something so simple, yet causing so much grief. UHGGGGG!

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2938096
06/29/21 04:49 PM
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Glad you got it fixed. up

Re: Gas is leaking from rubber grommet [Re: KZ4406] #2938304
06/30/21 11:23 AM
06/30/21 11:23 AM
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Originally Posted by KZ4406
Something so simple, yet causing so much grief. UHGGGGG!



those "simple" things are the cause of much learning of "new" words ! biggrin
glad you got it fixed, and shared the cause with us ! bow
beer







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