EFI Fuel Tank Vent

I have installed a 1991 mustang efi wiring harness with explorer gt40 intakes. I am using a plastic 1968 style fuel tank and filler hose. I used a tank's inc fuel pump module and it comes with a vent port. I read on there website that it hooks to a roll over valve seen here: http://www.tanksinc.com/index.cfm?ptype=results&Category_ID=160&home_id=-1&mode=cat

I did remove the purge cyl plug, tab and tad and plan on running an egr simulator. (old heads that I did not see any egr ports in could be wrong here but I don't remember seeing any)

Should I just get the roll over vent and install?
Should I wire the canister purge back into the harness and the tab and tad?

If I go with the canister purge how do I plum that up and what evap canister should I look for?? (limited to ebay no close junk yards)

Now is the time if I need to add items back into the harness as it is not totally installed yet and would be easier now.

I don't really want any fuel vapors etc.

Thanks

cbfomoco said:

I have installed a 1991 mustang efi wiring harness with explorer gt40 intakes. I am using a plastic 1968 style fuel tank and filler hose. I used a tank's inc fuel pump module and it comes with a vent port. I read on there website that it hooks to a roll over valve seen here: http://www.tanksinc.com/index.cfm?ptype=results&Category_ID=160&home_id=-1&mode=cat

I did remove the purge cyl plug, tab and tad and plan on running an egr simulator. (old heads that I did not see any egr ports in could be wrong here but I don't remember seeing any)

Should I just get the roll over vent and install?
Should I wire the canister purge back into the harness and the tab and tad?

If I go with the canister purge how do I plum that up and what evap canister should I look for?? (limited to ebay no close junk yards)

Now is the time if I need to add items back into the harness as it is not totally installed yet and would be easier now.

I don't really want any fuel vapors etc.

Thanks

Click to expand...

I will answer parts of your questions...
TAB/TAD are used on the smog pump, they control the valves that direct the smog pump's output to the back of the heads during warm up and then when warm, that output is directed to the CATS. If you do not have a smog pump and all the related parts, with a CAT, then there is no point to making this system active.

For the canister purge, that is what will help with gas vapor smells. I would try and locate a 87-93 mustang Charcoal canister and all the related parts. Canister, purge valve, with harness, and vacuum lines. Then hook it to an unused vacuum port on the upper intake. The purge valve typically only opens during cruise, so at sustained 2000 rpm or so. In the Mustang set up you will see 90* vacuum line off the CC with a plastic connector, then a straight line of vacuum hose. That plastic connector between the the hoses has a restriction in it that is not removable. Be sure you get the right one. The line from the tank to the CC typically comes off the top of the fuel tank, where the roll over valve is located on some tanks. I really cannot comment on your 68 tank, with a 68 filler and I am assuming 68 vented cap?

Remember with EFI you need a pressure line and a return line. Then the tank has to breathe, fuel the goes out, air comes in to replace it. If you add one of the remote tank breathers, then it could act as a point for gas fumes to escape...

You can mount the Mustang canister like this... 76-77 style.
This is a Mustang replacement canister I purchased from O'Reillys...

I have my vent going from the mustang canister to just in front of the MAF. You want it to be measured. Otherwise you will have excess air the computer doesn't know about.

duffymahoney said:

I have my vent going from the mustang canister to just in front of the MAF. You want it to be measured. Otherwise you will have excess air the computer doesn't know about.

Click to expand...

The size of the restricter in the factory vacuum line fitting is very small, so you are not pulling a quantity of air that will affect engine performance. By comparison, the port you have added is huge.

I am in the middle of installing the same evap system on my mustang FI. My harness has no provisions for canp valve so for simplicity I was planning on installing the engine vapor canister vent very similarly to how duffymahoney did. Are there draw backs to doing it this way?

canzelc said:

I am in the middle of installing the same evap system on my mustang FI. My harness has no provisions for canp valve so for simplicity I was planning on installing the engine vapor canister vent very similarly to how duffymahoney did. Are there draw backs to doing it this way?

Click to expand...

I think a number of people on this board have tried this and had success.
The issue I see is that the CC system and tank will always be under a vacuum while the engine is running. As long as the air is replaced there should not be a problem. But where is it pulling air from? From on of the CC vent mushrooms? or directly from the tank? I do not have an answer for that...

A fox mustang build shop told me to measure the air. The hose is small. I think 5mm or so. It's probably a giant overkill.