UPDATE! Gas coming out of fuel neck nozzle...

notnilc20
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UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Thu Sep 19, 2019 10:06 pm

was at the pump to fill up my gas tank and while I was pumping, gas starts coming out of the fuel filler neck and so I remove the fuel nozzle from the neck and gas keeps coming out spilling all on my nice new paint. However, the weird thing is, is the tank is not full but gas kept coming out of the neck. So I put the cap back on and it sealed it up and I drove home. Then I opened it back up and gas was still coming out...a little more slowly now. So I put the cap back on and took off the fuel level sender to see if maybe the tank was full indeed...however it was only about 3/4 full. How can gas come out of the neck and the tank is not even full? it is a new Spectra aftermarket fuel tank. any help is appreciated. thanks.
Last edited by notnilc20 on Tue Oct 01, 2019 9:00 pm, edited 1 time in total.

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jondee86
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Re: Gas coming out of fuel neck nozzle...

Postby jondee86 » Fri Sep 20, 2019 1:58 am

It seems like your tank is not venting.

Image

As you can see the filler neck enters quite low on the tank. When filling, once
the fuel level covers the tank end of the filler neck, the fuel will start to compress
a big pocket of air in the top of the tank. If that air is not vented, eventually it will
prevent any more fuel entering the tank and cause fuel to spill out the filler neck.

Then, as the fuel most likely came from an underground tank and was cool, it will
mix with the warm fuel that was left in the tank and start to expand. This will push
fuel out until the temperature of the fuel in the tank stabilises.

Normally the vent system should relieve the pressure and prevent this problem. If
you have removed and plugged your charcoal canister line, that could be the reason
that the tank does not vent.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

notnilc20
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Re: Gas coming out of fuel neck nozzle...

Postby notnilc20 » Sat Sep 21, 2019 9:53 am

yeah I think you're spot on. I still have the charcoal canister hooked up but I need to go back and make sure it's all correct. i did remove the egr system.....would that have any effects? thanks

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jondee86
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Re: Gas coming out of fuel neck nozzle...

Postby jondee86 » Sat Sep 21, 2019 3:25 pm

Actually.... after thinking about this and digging up this old thread....
https://www.club4ag.com//forums/viewtop ... 50#p108382
... I don't really know how your tank is supposed to vent :?

If the charcoal cannister is connected to a BVSV and the BVSV is open because the
engine is hot it might work a little bit. But gas goes into the tank a lot faster than
air can bleed out of the charcoal cannister... so where is it supposed to go ? Modern
cars have a vent tube that runs back from the tank and connects into the filler neck
just below the cap to get around this problem..

FWIW back in the day before auto shutoff nozzles were invented, it was not unusual
to get gas belching out of the filler neck if you were not quick enough letting go of
the trigger. You had to listen until you heard the sound of gas backing up in the
filler nick and that was when you stopped pumping. Maybe you just tried to push
a bit too much gas into the tank or the auto shutoff did not work ?

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
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notnilc20
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Re: Gas coming out of fuel neck nozzle...

Postby notnilc20 » Sat Sep 21, 2019 8:26 pm

jondee86 wrote:Actually.... after thinking about this and digging up this old thread....
https://www.club4ag.com//forums/viewtop ... 50#p108382
... I don't really know how your tank is supposed to vent :?

If the charcoal cannister is connected to a BVSV and the BVSV is open because the
engine is hot it might work a little bit. But gas goes into the tank a lot faster than
air can bleed out of the charcoal cannister... so where is it supposed to go ? Modern
cars have a vent tube that runs back from the tank and connects into the filler neck
just below the cap to get around this problem..

FWIW back in the day before auto shutoff nozzles were invented, it was not unusual
to get gas belching out of the filler neck if you were not quick enough letting go of
the trigger. You had to listen until you heard the sound of gas backing up in the
filler nick and that was when you stopped pumping. Maybe you just tried to push
a bit too much gas into the tank or the auto shutoff did not work ?

Cheers... jondee86


Hmm.....the auto shut off did activate while I was pumping but I took it as a premature shut off because I knew my tank was much more empty than what I had pumped so far. So I kept pumping some more and it pumped for a little bit longer then it started to overflow on me. When I got home I took the fuel level sender out to visually see the fuel level in the tank and it was not full....it was about 3/4 full. I appreciate your time and help as always Jondee86. I'll check my charcoal canister set up and update later. thanks again.

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Re: Gas coming out of fuel neck nozzle...

Postby jondee86 » Sun Sep 22, 2019 2:52 am

Yeah... I'm not familiar with exactly how the USDM venting works. My (Euro spec) car
doesn't have a charcoal cannister. There is just a loop of vent tubing that rises up above
the tank and then drops down with a little filter on the end. So basically vent to atmosphere
for those markets that didn't have strict emission laws back then.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
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Re: Gas coming out of fuel neck nozzle...

Postby notnilc20 » Tue Oct 01, 2019 8:53 pm

Ok so I finally needed more gas and so I filled the tank up again and came home and parked in the garage....about 20 mins later a strong smell of gas coming from the garage so I walked around to the fuel door and there is a puddle of gas on the ground so I opened the fuel door and there was gas leaking out. Unscrewed the gas cap and gas was sitting in the top of the neck nozzle so I popped the hood and checked the charcoal canister like Jondee86 suggested and I saw on the top of the canister 2 lines at the top of the canister one said purge (see pic)
Image
followed the line to the back of the head (see pic)
Image
and I had capped it off when I deleted the egr system. uncapped it and went back to check the fuel nozzle and the gas was already backing down the nozzle. Looks like it's fixed. Thanks again Jondee86.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby allencr » Sat Dec 21, 2019 8:08 am

The tank's filler neck has a small tube inside it that goes down past the end mounting & turns up into all that space above the entry into the tank, it's a vent. The stock tank, not the poorly soldered aftermarket.
When that tube gets fuel in it, like the airlock/p-trap on a kitchen sink,it stops venting the top of the tank. The EGR stuff works too, when it is OK but is kinda slow.
Either blow it out, it will fill up again, or IIRC that tube may not positioned correctly from the factory & needs to be bent up/vertical.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Sat Dec 21, 2019 10:49 am

allencr wrote:The tank's filler neck has a small tube inside it that goes down past the end mounting & turns up into all that space above the entry into the tank, it's a vent. The stock tank, not the poorly soldered aftermarket.
When that tube gets fuel in it, like the airlock/p-trap on a kitchen sink,it stops venting the top of the tank. The EGR stuff works too, when it is OK but is kinda slow.
Either blow it out, it will fill up again, or IIRC that tube may not positioned correctly from the factory & needs to be bent up/vertical.


Ok so where is the vent tube? because I dont see one on my spectre aftermarket one. I have a civic and I see another hole (vent tube) next to the main filler line but nothing like that on my spectre. It does have something that looks like it could work like a vent....I'll post pics later. now I can get a little more fuel in but it doesnt seem to fill up completely....it's very frustrating. I'd like to finally get this nipped.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby aukword1 » Tue Dec 24, 2019 7:48 am

follow the lines coming from the gas tank, there should be three of them. The easiest way for me to find mine was to put a rubber hose on the opening and blow air into it. If you hear/feel the air making bubbles at the other end, that is your vent tube. When blowing on the other one it will feel like its clogged in a sense.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby jondee86 » Thu Dec 26, 2019 9:09 pm

A long time ago in a galaxy far, far away, jondee86 wrote this...
To prevent blowback of fuel out the filler pipe, the vent must enter
the filler neck higher than the end of the filler nozzle. That is to say,
the rising fuel must hit the end of the nozzle before it covers the
end of the vent pipe. The attached pic shows how...

Image

http://www.agcoauto.com/content/news/p2_articleid/242

As far as I can see the AE86 did not have a vent tube on the outside of the
filler neck. My car didn't have one and the tank vent ran from the pump
mounting plate up high on the underbody above the axle and then down
again with a small filter on the end. So vent to atmosphere system.

USDM cars had EGR and a charcoal conister, so presumably the vent line
should have been able to handle the fume displaced by filling the tank ?
Otherwise it would have to vent back out the filler neck which works OK
apart from the odd blowback of fuel. Someone check an OEM USDM tank
to solve this mystery please :)

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby davew7 » Fri Dec 27, 2019 3:37 am

The USA gas tank for an AE86 had to 2 vent tubes right above the main filler hose connection. There was also a vent tube on the fuel pump mount, along with the output and return tubes.
Davew7

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby jondee86 » Fri Dec 27, 2019 6:58 pm

OK... bit of digging and I found this pic on an old club4AG for sale post. Said to be
a USDM OEM GTS tank and I have no reason to doubt that.

Image

Reason I never saw one before is that the vent tube is INSIDE the filler neck
and you don't get to see it unless you take the filler neck off. I have an old JDM AE86
tank that I am going to junk, so I will pull the neck off that and see if there is anythng
similar inside.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Fri Dec 27, 2019 7:22 pm

wow, thanks guys for all the help. I wonder If I take the fuel level sender off and put a flex cam in there If I'll be able to see the vent tube that is pictured above? I may try that next time I feel like messing with it. I just finished rebuilding my honda civic d16y8 engine so I need a small break, but I'll def do it sooner or later.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby jondee86 » Sat Dec 28, 2019 12:15 am

Dang me !!!! I just pulled the neck off my old tank and there is provision for a vent
inside the neck. You would never know it looking in from the top of the neck but you
can work it out when you take the neck out of the tank. Didn't have my camera so
I make a sketch :D

Image

There is a short piece of steel tube with an S-bend that is attached inside the tank.
That lets air into the filler tube at a level about an inch lower than the top of the tank.
The air then travels up behind a curved piece of steel attached to the inside of the
neck. There is a small gap at the edges of this "inner lining" and the neck so that the
air can leak out from behind the lining and enter the neck 3-4 inches from the top.

So there ya go... maybe the USDM filler has something similar inside ?

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby davew7 » Sat Dec 28, 2019 5:21 am

I do not think that type of vent inside the filler neck would pass emissions in the USA even back in the late 80's. Some states [Calif] even required the gas pump nozzle to seal against the filler neck while filling the gas tank to prevent vapors from escaping. That type of system required capturing the displaced air. There appears to be a hell of a LOT of different gas tank designs! Davew7

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby jondee86 » Sat Dec 28, 2019 12:53 pm

Yes... all the venting systems described in this thread only help in getting more
gas into the tank and preventing blowback/premature nozzle shutoff. Comparing
the size of the gas pump filler nozzle with the size of the vent line to the charcoal
canister, it is obvious that air/fumes will always be pushed out of the filler neck.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Sat Dec 28, 2019 5:57 pm

Here is a pic of my spectre gas tank nozzle. You can see the 2 small what appears to be vents above the main fill hole. However when I push the spring loaded plate back, all the holes share the same tube it appears. So it seems it is more similar to the diagram that Jondee86 sketched above??
Image

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby allencr » Sat Dec 28, 2019 9:13 pm

Thank You jondee86!!
Aftermarket isn't smart enough to include a necessary feature, but they are smart enough to know you aren't going to return it.
All it needs is a vent like the agcoauto pic jondee86 posted, it doesn't have to be too big, even 1/8in 4mm ID oughta be just about large enough.
It doesn't need a check valve, and as an added bonus, it self drains & can never get filled & air lock like the factory tube.
Good luck.
Happy New Year.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Sat Dec 28, 2019 10:21 pm

allencr wrote:Thank You jondee86!!
Aftermarket isn't smart enough to include a necessary feature, but they are smart enough to know you aren't going to return it.
All it needs is a vent like the agcoauto pic jondee86 posted, it doesn't have to be too big, even 1/8in 4mm ID oughta be just about large enough.
It doesn't need a check valve, and as an added bonus, it self drains & can never get filled & air lock like the factory tube.
Good luck.
Happy New Year.


yeah, I see. That might be the next project for the 86. Could I jist have a bung at the top of the tank and have it vent to atmosphere? Thanks a lot.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby allencr » Sat Dec 28, 2019 10:58 pm

Yes, if you consider all the charcoal canister & fuel vapor stuff as BS.
Gasoline used to take a long time to age, now with the alcohol(or maybe even without) it ages quicker, and venting to atmo might make it even quicker.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby davew7 » Sun Dec 29, 2019 6:17 am

notnilc20
" next project for the 86. I just have a bung at the top of the tank and have it vent to atmosphere?"

As I mentioned, there is already a vent tube on the fuel pump mounting bracket. No bung needed. Just add a hose to the current vent tubing that makes an up-ward loop. Make the loop as high as possible when attaching the hose mounting . I used that vent tube method for my gas tank. I did add a small filter to the end of the vent hose plus a check valve. [the check valve prevents roll-over slippage] You can get a gas tank vent check valve that fit inside the hose for a motorcycle shop.
Davew7

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Sun Dec 29, 2019 7:32 am

allencr wrote:Yes, if you consider all the charcoal canister & fuel vapor stuff as BS.
Gasoline used to take a long time to age, now with the alcohol(or maybe even without) it ages quicker, and venting to atmo might make it even quicker.

ok thanks a lot.
davew7 wrote:notnilc20
" next project for the 86. I just have a bung at the top of the tank and have it vent to atmosphere?"

As I mentioned, there is already a vent tube on the fuel pump mounting bracket. No bung needed. Just add a hose to the current vent tubing that makes an up-ward loop. Make the loop as high as possible when attaching the hose mounting . I used that vent tube method for my gas tank. I did add a small filter to the end of the vent hose plus a check valve. [the check valve prevents roll-over slippage] You can get a gas tank vent check valve that fit inside the hose for a motorcycle shop.
Davew7


I have that line from the fuel pump mounting bracket but it seems that it doesnt vent quick enough because the fuel going in is at a fast rate. So maybe another vent would help out. I was thinking I will remove the tank and fab an external vent tube from top of tank to the filler neck like the agcoauto pic jondee86 supplied. thanks for everyones insight into this. I really aopreciate it.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby mad_86 » Wed Jan 29, 2020 12:39 pm

My gas tank filler tube has a Air tube , Zenki USDM coupe
When i take off gas cap theres an extra hole for venting.

Plus vents off fuel pump bracket at (charcoal cansister & egr removed)

notnilc20
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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby notnilc20 » Wed Jan 29, 2020 1:21 pm

mad_86 wrote:My gas tank filler tube has a Air tube , Zenki USDM coupe
When i take off gas cap theres an extra hole for venting.

Plus vents off fuel pump bracket at (charcoal cansister & egr removed)

do you have a picture you could share? thanks.

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Re: UPDATE! Gas coming out of fuel neck nozzle...

Postby Nick94tt » Fri Jan 31, 2020 11:22 am

Zenki usm, can't quite pull the filler down to check the other side for a separate tube, plus it's cold out. :lol:

I've had similar issues losing fuel if I top the tank off, though I'm pretty sure my issue is a failed or just missing gasket under the locking ring given the previous owner didnt bother centering the filler neck - and connected the fuel pump wiring with masking tape and about 2 loose twists... :lol: )

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