filler neck questions again

[mark]

i looked over the setup again and there was a kink in the big rubber hose right after it came through the x member.(as i try to fill it with gas ,a lot leaks down the side)i put a hose clamp on forcing it round again and took it down to get 10 bucks worth of gas in.it did take it at the low setting but anything higher and it would come right back out of the filler hole and down the side of my rig.the fillerneck in this older rig has no flapper for the smaller unleaded nozzle.now i can kinda see how the vent system works.it goes right back up to the fillerneck.maybe ive got something wrong with the way im venting mine causing a prob.i have everything hooked up stock but i dont use the return line back to the tank so i ran a hose from it to a breather mounted under the frame.do you think this could be causing some type of vapor lock?if the return isnt used should it just be plugged?
i think im gonna pull the big hose off of the poly tank and run the garden hose with water through it just to see that it flows smoothly 1st.
any other suggestions are appreciated.
i dont really care about filling it fast anymore i just dont want it flowing down the side of my rig.
ill try something next week today im trying to get a stock fan with a clutch to somehow mount in my rig and ditching the electric one i bought.

[Chevelleguy]

The fill neck hole on the poly tanks are very small, just a little larger that your thumb. Have you pulled the hose off to check for a restiction?
My 83 Wag has the stock hose and has no problems.

[Elliott]

Every Cherokee I had was a total PITA to fill, just like you describe. Always had to use a pump located on a grade and pump at the lowest setting.
The best setup I came across was when I had dual tanks and the rear filled first... flooding into the forward tank. This eliminated the long, nearly horizontal filler tube to the front tank.

[mark]

if i dont use the return line can i just cap it off?i made it into a breather but that may not be doing anything if the tube goes down to the bott of the tank.if the gas cap is vac tight does that mean the whole system is vac tight?maybe i shouldnt try to vent it at all but i thought it had to be vented somehow besides the filler vent which is still inside the cap.

in other news .......
i just removed the 2950 cfm electric fan i mounted as a puller behind my rad.the 502 would not stay cool at idle with just the elec.i pulled the clutch fan off of my old rig and put it on the bb chevy and it seems to run cool at idle now.its been idling for 40 min now and its still running cool.
one down .....many to go! :D

[ August 24, 2003, 12:08 PM: Message edited by: mark ]

[Elliott]

While not a complete wiz at the fuel systems (although better then most of the dealer's mechanics) I don't think you should plug the return line. Doing so may cause excessive pressure to the carb, it is supposed to have a loop in it. Also, the system is supposed to be closed on the later models and vent into the charcoal can to be sucked up by... carb or manifold or something that sucks on those things.
Somebody here will have a fix for you....
WHO HAS A POLY TANK THEY CAN FILL????

[Wesdog]

Mark, I recall that you don't have the 1/4" vent lines, check valve and charchol canister. I also ASSUME you aren't talking about the fuelpump / filter return line to the tank in your initial post.

The 3/4" vent hose allows air/vapor to escape back to the filler opening as you fill the tank. Ideally, the 3/4" vent hose should be connected to the filler neck so the vapors will be sucked into the vapor recovery system on the gas pump nozzel as the tank is filled. A smaller size vent is probably insufficient for filling the tank efficiently.

When fuel warms up it will expand. If the tank is full and the tank's 3/4" vent is not connected to the filler neck then liquid fuel will leak out the the 3/4" vent hose and also the 3/4" nipple on the filler tube if it isn't capped. If you cap them both the tank will have to expel air/vapor back through long filler tube path when filling the tank and that will make it harder to fill. It seems best to me to connect the 3/4" vent hose to the filler neck as designed. If a non-vented/pressurized gas cap is used then the system will pressurize to the gas cap's rated relief pressure before opening and expelling fuel/vapor. If you want to provide a vent then put a TEE in the 3/4" vent line near the tank and run that to a breather that is in a safe location. You could even tee off the 3/4" hose to a stock liquid check valve and from the valve to a charchol canister like the 79 setup you had. Make sure any liquid will drain back to the tank as the level decreases.

The 1/4" vapor vent lines and check valve that I assumed you don't have are designed to vent vapor to the charchol canister. However, if liquid fuel in a full tank warms and expands to the point of reaching the check valve, the check valve closes and then there is no pressure relief path for the system except through the gas cap pressure relief valve or a leak if one exists. If you use a vented cap then liquid fuel will just escape out the cap if the fuel expands enough.

One thing that may help the fill problem is if the rear of the vehicle is slightly higher than the front so the the fill path is down hill. Or if you could tweak the filler tube so the liquid runs down hill except at the x-member that would help.

It would be helpful to know exactly what openings your tank has. The possible one's I am aware of are the 1.5" filler, 3/4" vent, one or two 1/4" vents, 3/8" or 5/16" fuel pump feed and the 1/4" fuel pump/filter return. What does your tank have?

One other idea is to install an expansion tank that is in series with the 3/4" vent hose between the tank and the filler. The 3/4" vent from the tank would be connected to the bottom of the expansion tank and liquid fuel would then have a place to expand to similar to a cooling system expansion tank. When the fuel cooled or the level dropped as the fuel was used the liquid in the expansion take would return to the main fuel tank to be used. The top of the expansion tank would be connected to the 3/4" filler nipple so you have a tank vent when filling the system. You could also connect a vent from the top of the expansion tank to the check valve /canister set up to prevent pressure buildup in the system.

My 76 Cherokee has the check valve setup and my 77 is like your 76 and only has the 3/4" vent. I am probably going to install the metal filler I previously showed you and also put a tee in the 3/4" vent line to a check valve and then on to a canister like I mentioned above. Haven't done it yet so I don't know if that's the answer to all the problems.

[ August 24, 2003, 04:05 PM: Message edited by: Wesdog ]

[mark]

WESDOG
you are a fuel genious!thanks.ill check into everything you stated and get back to you.these things i do know.

1- its a poly tank with i believe a 1.5 inlet(its not small like my 79.

2-there is no charcoal canister at all.(prolly removed by the po

3-there is no flapper where the gas nozzle goes in.

4-the 3/4 vent hose goes from a fitting screwed into the tank by the big main inlet,up the wheelwell to the top of the fillerneck.

5-i ran a pc of tube from the other fitting in the sending unit on top of the tank to a small kn filter.

ill look into the rest.
thanks for your expertise! :D

[Wesdog]

Mark, I think I understand how you gas tank is setup now.

The gas tanks without the 1/4" vent lines, liquid check valves and canister are meant to be used with a vented gas cap. And as you may have discovered if the tank is full and the gas warms up and expands liquid fuel is forced out the filler opening. The filling problem is separate from the venting issue.
It appears you have the 3/4" vent line connected to the filler nipple as it should be.

Regarding the kink in the filler hose: that may be the result of using the plastic tank with the original hose. Whatever the cause of the kink it probably needs to be corrected somehow. You might be able to get a piece of 1.5" steel tubing bent to the correct angles by a muffler shop to replace bent/molded part of the kinked hose and just use straight pieces of 1.5" fuel hose and clamps to tie it together. Hope that makes sense.

I assume you connected the small K&N filter to the fuel pump return line to help vent the tank. I think my suggestion of a TEE in the 3/4" ventline and the use of a check valve and canister is a better venting option but it also won't solve the fuel fill problem. Still, I would recommend using the fuel pump return to the tank for its intended function. It may help vent the tank the way you have it setup especially if you are using a non-vented / pressurized gas cap. I just think the fuel return from the fuelpump is important to prevent vapor lock. And if the fuelpump return tube inside the tank extends down into the fuel it won't help vent the tank.

I think you will need the metal filler tube to fix the fuel fill problem and prevent the fuel from backing up and spilling out the opening. The problem will be adapting the 1" end of the filler tube opening to the 1.5" underbody filler tube. I'll bet there is a plumbing adapter that will make that simple and I will be investigating that myself.

[ August 26, 2003, 06:57 AM: Message edited by: Wesdog ]