So, there's several other CRX's and Hondas up here that remove the charcoal canister and leave the fuel vent line on the firewall uncapped and exposed. Never an issue, never problem and yet we ALL run a turn down exhaust before the tank.

This, has also never been a problem for me either, until recently. At the triple event in Spokane I noticed a lot of fuel coming out of the vent line. At the last race at Pacific raceways, I tried running the vent line to TB which was an awful idea as straight fuel was just being dropped into my manifold and made the engine cut out. I then routed vent line to a Gatorade bottle and after a 20 minute qualifying session the large gatorade bottle was half fuel of fuel (not safe).

I replaced the two-way valve on the top of the fuel tank... same result. So for the race I just screw it and plugged the damn thing. When I took the fuel cap off, it popped off with quite the gusto! Of course the tank was pressurized but I'm still scratching my head saying, "WTF!".

How does my car develop this issue out of the blue? (BTW: it is possible that the two-way valve I swapped out was bad as well as it was an old one from an old car).


Any ideas? any suggestions? BTW: re-installing the charcoal canister won't fix this, as that would just fill up with fuel as well. The problem is what's allowing the fuel to end up in the vapor-vent line to begin with.

 

I had a similar issue, i drilled a very small hole in the gas cap to relieve the tank pressure. This was fine until i ran a hour race and i ended up with gas down the side of the car.

I have since removed the factory vent line and valve and have run a steel braided hose from the tank to the rear of the car and installed a breather vent.
Haven't tried this setup yet.

 

i had the same issue. just ran the line on the firewall to the catch can. mine only puked fuel under braking with a full tank tho.

 

Get one of these and run the vent tube into it.
http://www.summitracing.com/parts/SUM-G1504/?rtype=10

Drill a slighlty smaller hole than the hose, and run that puppy into it, and down near the bottom.
Not only will you catch excess fuel, but the fuel that i will catch is vented, and you wont get the popping sound when you open the gas cap..
Nope no gusto after that is installed.
Drain it after every run.

 

I like the idea of that but I don't know if I want to store a bottle of fuel in my engine bay, which that essentially accomplishes, then there's the extra task of emptying it all the time.

What I'm curious about is why did this *start* happening. I've left the vent line open for years. Haven't changed the exhaust, the tank, or anything that would affect it. Do the 2 way valves go bad easily?

At the next race I'm going to go with a 3 step plan.

1: Install brand new 2 way valve on tank
2: If that doesn't do it, try a vented gas cap
3: If fuel comes out of the cap then run the vent line out the back of the race car and let my competition deal with it.

In all honestly, the thing that's nagging at me most is why did it start happening? and why doesn't it happen to others?

 

I have never emptied more than a few tablespoons of fuel if any at all after a run.
I am curious to know what in the hell is causing that.

Seriously though you have to resolve the issue because spilling anything on track is a danger.
Letting your competition deal with it isn't the answer.
Sooner or later a meatball flag will be shown to you in your honor, and off the track you will have to come to correct it.

 

It is possible that the turn down exhaust is heating the tank too much and this didn't rear its ugly head until a race in Spokane where the ambient temps were quite warm.

Perhaps I should put some heat reflective material against the bottom/front of the fuel tank to keep the hot exhaust gasses from heating it. Possible heat shield.

In looking at vented gas caps, none of them give any idea of how much pressure before they vent, unless they are just "open" vents. I also don't want a meatball for fuel spilling out of my fuel door during hard right hand turns.

 

Try taking off the valve and blowing air through the vent tube to see if is clear, if it is clear try listening to where the air is coming out the other side , the tube exit is welded along the top right rear of the tank(where the hump is). That is the highest point of the tank where there is no fuel. Perhaps your tube has broken off inside or cracked.

 

What kind of exhaust do you have and where is it turning down at?
My redshift exhaust turns down at the LCA and i have no heating problems, even with out a heat shield.
Must be something more like what essex is describing.

 

The "nip" on the gas tank that the line from the 2-way valve connects to is part of the tank. So if what essex is saying, the only way to replace it is to replace the tank. However, how would that break if there was indeed something inside the tank?

 

this is how the tube runs in your tank. Is it old? If it's a newish tank I wouldn't worry about it , I just thought I read you haven't replaced the tank, you can just blow some air through the whole line from under the hood as well and that should unclog it if something did get in there.

 

Essex, this is exactly the info I was looking for. I will try that tonight after work. I already blew air from the port on the firewall back to the 2-way valve but it was disconnected from the tank at the time so I did not blow air through the vent line on the tank to listen to where it comes out in the tank.

Regardless of weather or not this helps, I could not find this info out anywhere else. Next time you're in the PacNW, I'll buy you a beer.

 

Oh I think if you just put it up to your mouth and blow on the valve it should work too , one way and not the other, probably a not a good idea to run compressed air through that the wrong way :D

 

Bicycle pump!

 

did you solve your issue yet?

 

Why do you even have the vent tubing running through the floor of your interior up to your engine bay? Unused dead weight and a safety hazard, I removed the entire vent tubing and rerouted the tubing up the tank filler neck zip tied to the height of the fill inlet cap on the exterior of the car and left it an open tube at that point. I also run an exhaust turn down that dumps just before the tank and have never experienced fuel expansion or enough vaporization to see raw fuel out of the open breather tube at the fuel cap height.

 

I ran into this problem on my old CRX, I would just dump fuel out of the vent and the cap. I had a turn down made for my exhaust that dumped in front of the LCA. Still did it, then i put new cap still did the same problem. My final cure was to make the exhaust exit the back of the car. I never had this problem again. At one point It sounded like the gas was boiling in the tank. not safe at all. But remember i am in fl and it gets hot down here.

 

What did you figure out?

 

I know with the Mustangs, they installed a bigger vent line to solve the problem, as a band aid.

The problem was the exhaust heating up the fuel if they had exhaust dumps. Most of them got rid of the dumps. Problem solved.

I know it was during the warm week or two for the Spokane Race. The week after, it was happening to alot of the ChumpCars.

 

In general, a fuel vent line should route from the gas tank vent to a high point, above the filler neck, and then go back down to a low point, lower than the bottom of the gas tank. The high point prevents fuel from spilling over when driving or filling up. The low point is in case the car ends up upside-down. In the vent line, between the gas tank and the high point, install an inline rollover valve for additional spillover protection. This allows air pressure venting, but if the valve is ever upside-down, it closes.

http://www.hrpworld.com/index.cfm?fo...action=product

I tried the vented gas cap idea, and it just spills gas all over the side of the car.

 

thank you very much...

 

Sorry to raise the dead here but I never answered this question.

My solution to my problem was to just cap the damn thing and have a "sealed" fuel system and I used an aluminum sheet to build a heat shield underneath the gas tank (exhaust dumps before tank so it helped that a lot).

After a 30 minute race I only get a small "pshhhh" when removing the cap.