8 replies to this topic

[RobSpec]

Hi all,
I have been having an issue with fuel sloshing out of the fuel tank when it is filled near full. I need it full for enduro's so running a half tank is not a good soultion. My car is an ITS class so I have removed the charcoal canister system. A vent is installed at the top of the tank which was fed to the breather just below the filler cap. The filler neck is completely gutted.
With this configuration I was getting tank pressure and sloshing that blew past the cap and leaked fuel out the drain. So I installed a catch tank in the trunk in the drivers side wheelwell. The vent now goes to this tank and then a separate hose vents back to the standard vent line. Even with this the vent line from the tank gets filled with fuel blocking air venting.
What have you all done to allow good tank venting and ease of fueling without causing fuel spillage? Any help is appreciated.
Thanks Rob

[Mike Collins]

Are you talking about fuel spilling when you add fuel during an enduro or the fuel spills after you get it to full then go out on the track?

[RobSpec]

Fuel burps out when I am running on the track. It appears to be due to a combination of sloshing and a lack of venting. I just can't figure out how to correct it.

Are you talking about fuel spilling when you add fuel during an enduro or the fuel spills after you get it to full then go out on the track?

[Johnny D]

No expert here.
I thought I remember someone saying you need to loop the vent tube.
And run the tube as high as you can and then down.
J~

[ChrisA]

Run some fuel line hose from the roll-over valve on the tank down to the bottom of the car. Make sure the hose is always directed downward so it will not trap fuel. Terminate the hose with a mesh screen type of inline fuel filter to keep debris out of the line.

[Mike Collins]

My guess is that without the check ball and the canister your fuel is expanding from excess heat from the exhaust. I see it all the time where with heat the 99's will run funny. Consider shielding the tank with a heat wrap from the exhaust.

[Glenn]

If it is a 99 you also need to see if fuel is getting into the canister under the hood. It will fill with fuel and then backfeed into the intake.

[RobSpec]

The canister under the hood has been removed along with all of the other associated emissions conrol stuff.
I am thinking about this discriminator valve from Fuel Safe. It would mount in the plate for the fuel pump and claims to block fuel flow while allowing airflow. 1/2 inch (An8) fitting.
http://www.polyperfo...ves-p-2821.html
With that I should be able to run to the stock vent line just under the fuel filler cap.
Anyone tried this?
Thanks Rob

If it is a 99 you also need to see if fuel is getting into the canister under the hood. It will fill with fuel and then backfeed into the intake.

[davew]

I understand that you have an ITS car, and that the rules allow removing the cannister vent system. I have seen numerous versions of this removal cause problems. My advise would be to simply reinstall the entire fuel canister system as supplied by Mazda. Then do one simple thing.

There are 2 small hoses that go from the fuel tank to the fuel filler neck. Remove one end of one hose from the tank. Remove one end of the other hose from the filler neck. then loop them back. Creating a loop from the tank back to the tank. And another loop from the filler neck back to the filler neck.

You can then gut the filler neck and not have fuel spill issues.

I have seen this at least 6 times, putting everything back will cure the problem

Dave