How to vent gas tank to a throttle body EFI

[mgb0302]

I have an MSD Atomic EFI. I have the basic 23 gal tank with the frame mounted pump. My tank creates a significant amount of (over) pressure inside (evident when I remove the gas cap and air comes rushing out). Although it does not significantly prevent the truck from running, I think the cavitation could be prevented.

My thought was to vent the tank by running a vent line back to the throttle body before the mass air sensors (like into the air filter) but without using a vent/ charcoal canister. My concern is, if the throttle body ever back fires (which it does on rare occasion), would this create a dangerous situation such as igniting the fumes from the vent line and then into the tank.

Much thanks

 

[DirtDonk]

A legitimate concern anytime gasoline is involved, but I don't think a fire could travel down that much tubing and ignite fumes in the tank.
I could be wrong of course, and would not want to assure you it won't happen. Just that I don't see it as a big issue.

But why not just use a vented cap?
What year is your truck? Pre mid-'70 prior to the evap system being implemented? If so your caps should be fully vented in both directions I thought.
Maybe doing something as simple as drilling a tiny hole in the existing cap would cure the issue?

I actually prefer your idea actually. Keeps the fumes from the atmosphere (and your garage!) instead of just venting haphazardly.
Maybe go the full tube-to-the-filter route, but install an anti-rollover or other similar one-way valve in the line. Probably even have flame-retarder versions available.
Problem solved!

Good luck.

Paul

 

[mgb0302]

Paul

Do you by chance know the canisters that most people use? I have heard of some using ones from a mustang. I am not opposed to using one, was just oping to make even more simple than that. But if I have to use a canister, I will.

Mike

 

[904Bronco]

Mike,

The CC used on the 88-93 Mustangs is what people have used... The canister itself is the same on a lot of Fords of that era. They just plumbed it differently.

I bought the one below from O'Reilly's, but it did not come with those mushroom breathers on the two large ports. I had to find them at the wreaking yard. Be sure the line from your tank has a check valve or rollover in it, so straight fuel cannot go directly to the CC.

 

[DirtDonk]

I love that molded-90 on that front port Doug! You should get more of those and use them to adapt the 3/8" fuel line to the other port as well.
Did it come with the tank, or is that a junkyard part as well?

Paul

 

[EBGeek]

I agree with Paul, I see no way a flame could travel down that much tubing. Not to mention how common of a setup the canister vent is. I have mine vented through my evap tank (behind driver seat) to help absorb some of the expansion and prevent fuel spillage on higher grades, then have it ran to one of the charcoal canisters under my hood.

However, even with all that room for expansion, I still get gas fumes when my tank is full. I deal with it by trying to only fill up when I'm going to drive it, but its in my plan to tie the vent into my air intake some way or another.

Some good reading:

http://classicbroncos.com/forums/showthread.php?t=198586

 

[Crush]

I plumbed the one in mine like my 84 mustang gt. Only i have only one small port capped and the other going to the tank vent via check valve on my canister and two large. Only one large has the mushroom and the other has a hose going to the air cleaner to recirculate the fumes i guess

 

[904Bronco]

I love that molded-90 on that front port Doug! You should get more of those and use them to adapt the 3/8" fuel line to the other port as well.
Did it come with the tank, or is that a junkyard part as well?

Paul

From a 88-93 Mustang as well, the vacuum hose connector on it has a restriction built in as well (mustang) I had Garry wire a purge solenoid into my 2000 Explorer harness. In theory, it will purge the CC while at cruise, like a mustang. It works on his bench, I guess I am the test mule to see if it works in a vehicle.