Where to run gas tank vent line with tank moved to rear of truck?

[WinDancer]

I have been having a terrible time getting fuel into my truck.

The filler tube from a suburban or Blazer was used.

The two vent lines from the tank, one went to the filler neck and the other was just plugged.

The second vent tube must be unplugged to add fuel.

Where might I run that second vent tube to be safe from fire?

What did you guys do?

Thanks,
Dave

[John Fabris]

With my set up, I made a hole 2 inches down from the top of the filler tube, and then welded an elbow fitting onto it, and ran the air vent hose to that. With a solid marine style cap, I have a closed system with the air vent only for filling. (The end of a gas pump tupe is around 3-4 inches long. That way out going air is exiting ubove the incoming air. Easy fill.

I added a vacumn check ball valve (from a motorcycle shop), onto top of tank and that relieves any vacumn created during fuel consumption.

As for your having to unplug the second hose, make me think that the first vent hose to the filler next is plugged...
How is your filler tube installed?

[chevydog66]

Hmmm, interesting. I too will soon be doing the Blazer tank conversion on my 72 GMC. I am subscribing to this one, just in case I have the same problem.

[Livrat]

Dave,
Good to see you back on line!

Did you remove/discard that flip down/push open lid gas cap that came with the street rod fill tube? if you remove that when filling, it should fill fine, The small hole in that lid it too close to the diameter of the gas nozzle and does not allow for the factory vent tube which is below the cap to do its job, creating pressure, hence spitting fuel back.

[leddzepp]

I have the same problem. One of the vent lines is attahced to the filler tube, the other is just plugged. Even though there is a vent line, I still have to unplug the 2nd vent line, or gas overflows.

[WinDancer]

Hi guys
John. I did rig mine just like yours, with the motorcycle ball valve. Still won't take fuel unless you uncap that line. I even installed the stainless marine cap, but then converted to a step-side. This is the new bed giving me the fits
Mark, I did replace the cap and am removing it to fill up. It takes it in only in very slow very tiny amounts. Until you open the other vent line. I think we opened that line the night I left from your place.
I don't want to keep reaching down there in a muck under the fender to find the dang valve an remove it.
This is the last thing left before I park the Ford and resume driving my baby every day.
The gorgeous filler door area is filled with the gas cap- no room to slip the valve in there, too.
LONNNNNNNNNNNNNNNNNNNNNNG ways from the gas tank to a canister and\or vacuum source.
I smoke and don't even want to consider having to watch out for the fumes. I generally mow near the truck, too.
What else are some of you doing? Short of converting to electric? How much IS a 400 horse electric engine anyway?
Thanks,
Dave

[Livrat]

Dave, since you have to remove the motorcycle ball valve to fill the tank, maybe it is plugged?

John.. maybe you can shed some light on this..
Here is a picture of Daves filler neck. it is a factory Blazer filler neck rotated 180 degrees. with the factory vent tube attached with the secondary vent tube with the ball valve. Any ideas??

[John Fabris]

Interesting, not much different then the way mine is set up, other then I have one less bend, but about 3-4" higher.
When you fill up, does the end of the gas pump filler tube sit lower then where the vent tube enters your truck's gas filler? (meaning when filler nozzle is inserted into your gas tank filler, does the end of the fill tube go past were the outgoing air vents meets the trucks filler tube?)

Only other question I could ask, is the gas filler hose under the bed level or inclined, and if inclined, towards tank or back towards fill upright tube?

Other then that, your set up only differs in the installation of the vacumn valve (mine is chemwelded to the top of the tank) but that has no relevance on filling tank.

Looking at your picture, I really want to say to verify that your vent tube to the filler has good flow and no blockage....

I hope you get this figured out. I have several friends with custom fill set ups, and slow fills are among their biggest compaints.....

Also, for clarification, when you guys have two vent hoses, is that two vents from the tank? or you you splitting one vent from tank into two?

[ETsC10]

Fellas, I've had to uncork that beastie to get gas in. It's down under the fender (subject to mud, etc) and maybe needs to be re-routed somehow. Could it be vented to above the gas tank on the right side under the bed where it's cleaner? Just guessing here...

[truckintexas]

Just jumping in here, but it looks like in the photos there is no way the pump spout can reach below the vent tube in the side of the filler neck. I think this would cause a situation where the filling of the tank is "fighting" against the venting thru the side tube.

Also, every blazer tank I have seen posted on this site has two vent tube outlets. I think this is because the vent volume needs to be almost the same as the fill volume to allow for easy flow of fuel. Some of you may remember, in the seventies and earlier, oil cans had to be opened with a can opener. You would punch two holes in the top (1 for flow and 1 for vent). And if the vent hole was too small, the oil would go bloop, bloop, bloop and flow very, very, slowly. But is the two holes were about the same size, flow was not a problem. I think we are experiencing the same thing here.........

[Classic Heartbeat]

I would think that if you used wire ties to tie both vent hoses to the bed cross sills that your problem would be solved. just make sure the end of the rubber vent lines are higher than the top of your tank. Use a breather valve in the end of the rubber lines to keep anything from getting into them. You could rout them to the inside of the rear cross sill also and that would protect them from debris. WES

[WinDancer]

Good stuff, guys, thank you!

The outside view of the filler assembly is deceiving- the vent hose actually goes into another pipe inside the visible filler tube, and runs up inside there for a ways, and that allows the gas nozzle to enter below the vent.

The main difference I see between this and my earlier setup is the diameter of the fill tube- the new one is smaller. And the vent breather used to be at the top of the filler, at the top of the bed side next to the stake pocket. I had a door built that covered the entire assembly with room for jumper cables, too.

So I have two problems here- filling it and safely venting it.

Wes, if the breather allows air out all the time what about the fumes and the fire danger?

I am not sure that my tank is from a blazer or Burb, the filler pipe going into the tank is larger than the fill tube, even if the fill tube did NOT have the second air pipe inside.

More ideas?

I cut a piece of the second tank vent hose and will pick up 12 feet of that tomorrow with a pipe to connect the two just so I can start driving it again.
I can tape the longer hose somewhere on the back bumper for a few days till I get this sorted out with a permanent fix.

With the second vent open it will easily at the slowest feed setting at gas stations.

[WinDancer]

Found this via google...

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You are here: Experts > Home/Garden > Auto Repair > Chevrolet Repair > Fuel Tank Vent Valve

Chevrolet Repair - Fuel Tank Vent Valve
Expert: C J S - 4/6/2007

Question
We have a 2004 Blazer that wont take gas. If you put it in a gas can it takes about 20mins to get 5 gallons in it. If you use a regualr pump the gas comes back out. We have heard it might be the vent valve. Do you know where it's located and if this can be done on your own. I appreciate any help you can offer.
Brandi

Answer
Hi Brandi,

It is the vent valve...most likely. When you put gas in the tank, it pushes out air that is in the space the gas is taking up. If the air cannot vent, the gas cannot go in.

The valve is located on top of the tank. It vents to the charcoal canister. It should throw a code. Emissions has caused cars to vent gas fumes to the pollution control system. But if this is plugged filling with gas, it should also be plugged emptying. You should experience pressure differences in the tank, enough to trip a code.

There is a rig up method to fill the tank, or you can get it fixed correctly. To rig it: go to a parts store; buy a gas rated small hose (1/4" or so)about 3 feet long; take cap off and feed the hose into the tank, leaving a little bit hanging out (so you don't loose the hose into the tank and can get it out); then fill the tank. The tank will vent out the little hose. Don't let the hose get under the gas level. You need to be above the gas level. This will get you by until you get the thing fixed.

Hope this helps.

C J S

Dave

[SuperJerrC10]

Hey livrat,

i didnt see a project built for a photo of the inner bedside fuel door. Could i bother you for one of that? the backside box bracket peecked my interest , like an article i saw on a "F*RD"(sorry bad word!) lately.

Thanks, jerr

[Gray Ghost]

I only used one vent but the gas comes out of the fill tube at the end of filling. I will add the other vent tube and see what that does.

I ran my vent hose up into the fender near the back....works fine as far as I know. Can't wait to add that second line after reading this....maybe I can fill it faster!

[Livrat]

Originally Posted by SuperJerrC10

Hey livrat,

i didnt see a project built for a photo of the inner bedside fuel door. Could i bother you for one of that? the backside box bracket peecked my interest , like an article i saw on a "F*RD"(sorry bad word!) lately.

Thanks, jerr

As requested, here is a couple...

[SuperJerrC10]

Super clean!! thanks!

jerr

[67ChevyRedneck]

My truck is really similar to yours. I put a motorcyle vent filler in my stake pocket, as you and several others have done. This should have NOTHING to do with your truck filling up. The valve only opens when the pressure of the fuel being sucked out of the tank causes a vaccum and then that vacuum causes the motorcyle vent valve to open and allows air to flow into the tank, it has nothing to do with filling the truck... so that tells me that there is something wrong with the fuller vent set up?

Is there any chance the line is pinched/plugged/restricted? I have the motorcycle vent hooked to one of the vents on top of the blazer tank's sending unit. I have a 88-98 silverado filler neck. I have to agree with truckintexas, it looks like on the factory blazer fill, and on my silverado filler, the vent tube is high on the neck, above where the spout goes into the tank. I too can't fill my truck with the pump on full speed, but it fills fine at half speed, without clicking and stopping.

What *MAY* be happening is that your vent tube is filling with fuel as the rest of the filler neck is filling with fuel, so there is no place for the air inside the tank to be displaced to, that may be why it will fill when you open your other vent, and the reason the factory places the vent at the "top" of the filler neck. I'd cut your vent off where it is now, move it to the top of the filler neck, fill the hole, and you should be good to go? Of course, take it off the truck first

This confuses me...

The outside view of the filler assembly is deceiving- the vent hose actually goes into another pipe inside the visible filler tube, and runs up inside there for a ways, and that allows the gas nozzle to enter below the vent.

Are you sure that it's not filling with gas too when you fill up?

Also, my tank has two vents:

1. Motorcycle vent that only functions when the truck is running/sucking fuel out of the tank and allows air to be pulled into tank.
2. One filler neck vent.

[ShortStepper]

Did y'all get the problem solved? I am putting a Blazer tank in my step side and hope to use a similar set up as seen on Windancer and Lemon Drop. Before I spring for more parts I would like to know if the setup works.

Thanks!

[6772owner]

Well guys I am kinda late on this thread but here goes anyway.... I put an aluminum fuel cell under bed and used a marine filler hooked up straight to the top of the cell (original filler hole) I have no vent line there what so ever. I then ran a vent line from the vent fitting in the cell to the front of the truck and hooked it up to the charcoal canister (original equipment on my 72') I have had NO filling issues, no fuel pump issues even at 1/4 tank and hadnt even given it a second thought since I installed it. Now I do have the factory 96' LT1 EVAP purge solenoid handling the vacuum duties to the canister, but I presume that any vacuum source would suffice. Just my .02

[WinDancer]

Yes, my setup works correctly now.
I ran the vent hose along the frame up into the engine compartment and installed another 90 degree PVC valve in the top of the air collector and ran the hose into that.
Because of the smaller blazer neck you can't fill at full speed, but it fills on the low setting now without clicking off.
I am very happy with it, the way it looks and the way it works.
Dave

[rodstored-72]

i have a similair situation. my tank is very slow to fill. i have both outlets vented (small ball valves like for a differential) & then the filler tube is ran up into the pass side rear wheelwell with a "cool cap". i have a really sharp bend (like 90degrees or so) from there to the tank. it seems to flow ok except at the very top. i am planning to "redo" it when i tear down for paint...... just my 0.02 cents

[mrnize]

Originally Posted by Livrat

Dave, since you have to remove the motorcycle ball valve to fill the tank, maybe it is plugged?

John.. maybe you can shed some light on this..
Here is a picture of Daves filler neck. it is a factory Blazer filler neck rotated 180 degrees. with the factory vent tube attached with the secondary vent tube with the ball valve. Any ideas??

Yes, brought from the dead.. Sorry

I see the valve there, Im having the gas up issue as well and looked at my tank and can only see the inlet for the pumped gas, then only the breather tube I guess that goes directly into the filler.

So what I want to know is, if I cap off the breather line that is inline of the filler tube, and put the one way valve on the second one will it "breathe" while gasing up??

Also, where do you get the gasket that goes behind the filler neck and the body? I have 74 fleet side short box.
Thanks

[Beuford]

My fill neck looks like "Livrat's" and I had problems too. I moved the vent tube from where it is in the pic to the top side of the neck about 2" higher. The gas nozzles don't go in deep enough and some gas was getting in the vent then it would puke and gurgle then I could put more gas in. I can run the nozzle wide open now. I have a 31 gal burb tank.

[cdowns]

on a fleetbed you can run a vent up between the bedsides with little problems