Venting for Fuel Injection Swap

[jrcr_15]

Happy new years!

Was hoping to get some advice / opinions. I am switching my car over to fuel injection with the Fitech Go EFI 2×4 1200 HP Power Adder (30064)

Additionally I am using the Fuel Command Center - which I plan on taking apart and modifying it into a return system to help keep it cooler.

My question really comes from the fact that I need to vent my fuel tank/system when I make the switch. I have read about people venting their gas cap / filler.

Currently I have a 71 style cap/filler with no venting. (I prefer that look as it is more flush with the body compared to the 72+)

I am however going to put in a new fuel tank. (mine is a bit rough) I am looking at a factory style for a 70-71 with 4 side vent tubes.

Would this tank provide adaquate venting? Or would there be modifactions required to the filler tube/cap?

I have never done a FI swap. Any help is appreciated. Thanks

 

[Steven190]

You can try Tanks inc, they have fuel injection ready tanks; Mopar Fuel Tanks

 

[kiss]

Fuel injection ready tanks are nice.
If you want to stick with a stock tank you will need to make sure your sending unit has a provision in it for a return line, or you will need to modify the tank.

I would not go with a '71 style tank. Go with a '72+ tank. Read my reply in this thread from earlier today in regards to that:
My Gassy-Smelling 71

Currently I have a 71 style cap/filler with no venting. (I prefer that look as it is more flush with the body compared to the 72+)

I don't really understand this statement. I just switched from a '71 filler neck/cap to a '75-76 (same as '72+ just unleaded style) filler neck and cap. It doesn't stick out of the body anymore than the '71 did.

 

[67Dart273]

I don't understand why you need to change anything so far as vent, some caveats:

If you have the "carbon can" setup the tube coming up front IS THE tank vent. You don't want to remove that, or if you do, make other allowances. You can run it "up high" in the engine bay to prevent spill over, and even plumb the end to the air filter bonnet to prevent "smell."

Otherwise, I'd replicate the 69/ earlier vent, which is a nipple welded into the filler neck "up high" in the trunk, with a vent tube run way up against the quarter "roof" and then down along the filler tube, pointing down and open into the cavity in the frame rail below the trunk.

I believe your car ?? had the separator can in the trunk??

Go to MyMopar download the 70, 71, 72 service manuals to get an idea of what they did, in the fuel section, and in the back, emissions section

Then get anything before 70 and look up how it was done

Earlier venting:

 

[famous bob]

I don't understand why you need to change anything so far as vent, some caveats:

If you have the "carbon can" setup the tube coming up front IS THE tank vent. You don't want to remove that, or if you do, make other allowances. You can run it "up high" in the engine bay to prevent spill over, and even plumb the end to the air filter bonnet to prevent "smell."

Otherwise, I'd replicate the 69/ earlier vent, which is a nipple welded into the filler neck "up high" in the trunk, with a vent tube run way up against the quarter "roof" and then down along the filler tube, pointing down and open into the cavity in the frame rail below the trunk. Oh, a non vented cap.

I believe your car ?? had the separator can in the trunk??

Go to MyMopar download the 70, 71, 72 service manuals to get an idea of what they did, in the fuel section, and in the back, emissions section

Then get anything before 70 and look up how it was done

Earlier venting:
View attachment 1715126910

I bought a replacement new gas tank off ebay. It had the filler neck vent which I ran down and out by the frame, pointed toward the rear, a lot of mopars came that way. It also had a vent tube sticking out beside the pick up, that was probably for a canister. (???) I ran it up thru thru
the trunk floor and created a couple of coils up high and back down thru the trunk floor to just below the frame. I have a fuel inj. set up and no problems. Using the orig pick up as a return line. jfyi

 

[jrcr_15]

Fuel injection ready tanks are nice.
If you want to stick with a stock tank you will need to make sure your sending unit has a provision in it for a return line, or you will need to modify the tank.

I would not go with a '71 style tank. Go with a '72+ tank. Read my reply in this thread from earlier today in regards to that:
My Gassy-Smelling 71



I don't really understand this statement. I just switched from a '71 filler neck/cap to a '75-76 (same as '72+ just unleaded style) filler neck and cap. It doesn't stick out of the body anymore than the '71 did.

Thank you for the information. What is the difference between a FI tank vs a normal one? Are they thicker?

I think the differnce is in the cap.

 

[dgibby]

Thank you for the information. What is the difference between a FI tank vs a normal one? Are they thicker?

I think the differnce is in the cap.

The Tanks Inc injection tanks are set up for an in-tank pump and return built in. They are also vented and come with the vent check valve that can be mounted where you want. The tanks are also baffled and kind of have a sump area for the pump. I remember reading somewhere not to vent the fuel injection through the gas cap, it wont work. Also, on a fuel sender with return built in, the return is only 1/4 inch, which is not big enough, according to Fi Tech or Holley Sniper. If your going to buy the command center and modify to work you might as well buy the Tanks Inc setup and forget the command center. Think mine ran $422.00 total.
If you do use the command center and don't modify it then all you need is a vent, not a return line, and that is very easy to add.

 

[famous bob]

The Tanks Inc injection tanks are set up for an in-tank pump and return built in. They are also vented and come with the vent check valve that can be mounted where you want. The tanks are also baffled and kind of have a sump area for the pump. I remember reading somewhere not to vent the fuel injection through the gas cap, it wont work. Also, on a fuel sender with return built in, the return is only 1/4 inch, which is not big enough, according to Fi Tech or Holley Sniper. If your going to buy the command center and modify to work you might as well buy the Tanks Inc setup and forget the command center. Think mine ran $422.00 total.
If you do use the command center and don't modify it then all you need is a vent, not a return line, and that is very easy to add.

MY fuel sender is 3/8", 43 pound pressure line is also 3/8".

 

[67Dart273]

T
I think the differnce is in the cap.

No Mopar cap is "vented." When Ma started installing the emissions vapor control (carbon can etc) the caps varied and were known as "pressure vacuum". These ARE NOT operational vents. They are pressure reliefs

There are ONLY THREE vent strategies over the years, which I've already touched on The last two are really similar

1....Up until the CA cars got evap controls, which started in '70 on some cars, the vent WAS ALWAYS the TEE fitting welded into the filler tube in the trunk

2...For a few years, the "carbon can" evap system had a vapor separator can in the trunk. A vent went clear up front, the 1/4" tube which connected to the carbon can system up front THIS IS the vent

3...Somewhere around 73? The trunk vapor separator was dispensed with, and the separator was incorporated into the top of the tank, resulting in ONLY TWO tank fittings..........the fuel supply on the sender, and the 1/4" fitting to the front. THIS IS the vent

 

[goldduster318]

I have the original 70 style tank in mine which has the vent in the top of the filler tube and an Aeromotive Phantom 340 kit in the tank and it works perfect. I would duplicate this.

On my friend's 71 Demon, we basically just put the filler neck in from the inside like on a '70, welded an AN weld fitting in -3 or -4, can't remember, and then duplicated the OE 70 setup.

 

[kiss]

No Mopar cap is "vented." When Ma started installing the emissions vapor control (carbon can etc) the caps varied and were known as "pressure vacuum". These ARE NOT operational vents. They are pressure reliefs

There are ONLY THREE vent strategies over the years, which I've already touched on The last two are really similar

1....Up until the CA cars got evap controls, which started in '70 on some cars, the vent WAS ALWAYS the TEE fitting welded into the filler tube in the trunk

2...For a few years, the "carbon can" evap system had a vapor separator can in the trunk. A vent went clear up front, the 1/4" tube which connected to the carbon can system up front THIS IS the vent

3...Somewhere around 73? The trunk vapor separator was dispensed with, and the separator was incorporated into the top of the tank, resulting in ONLY TWO tank fittings..........the fuel supply on the sender, and the 1/4" fitting to the front. THIS IS the vent

Few corrections here:
1. Through '70 (minus '70 CA) all cars had the vent line which went from the top of the filler neck down under the car. If you have this setup it's a good idea to add a small filter of some sort to the bottom of this so crap doesn't get inside it, or even just zip-tie a piece of screen to the end. This setup works but can lead to fuel smell since it vents directly to the atmosphere.

2. The '71 (and '70 CA) style vent setup was complicated. There were 3 vent lines and 1 vapor return line coming out of the driver's side of the gas tank. These went up into a vapor canister that is in the trunk leaning up next to the driver's side wheel well. Theres a 5th fitting from the vapor canister which goes to the passenger side of the engine bay via a 5/16" line. This line connected to the breather on the valve cover. The idea was that any fuel vapors would be stored in the crank case and when you start the car up it's sucked through the PCV system. In addition the external carb bowl vent was connected to a fitting on top of the fuel pump (slant 6) or a 3rd fitting on the breather (V8) to store its vapors in the crankcase as well. This design has several faults and if you ever have issues with it you'd be best served removing the vapor canister and gas tank and going with the '72+ design, unless you're trying to keep your car bone stock original.

3. The '72+ design is a big improvement from the '71 ('70 CA) design. Instead of the vapor canister and multiple vents nonsense it has a single fitting at the top-middle of the gas tank facing forward. This fitting was connected to a 1/4" line going to the passenger side of the engine bay. This was then connected to a charcoal canister. The external carb bowl vent was connected to this as well.

There's a good article written on Allpar about this:
Fixing 1970s Evaporation Control Systems

I personally have a '71 which I modified to a '72+ tank and removed the vapor canister. I did not add a charcoal canister, the vent line going to the engine bay has a small filter at the end to keep crap out, and it's not connected to the breather. I've had no fuel smell problems with this design because the vent line has such a long 'run' if you will.

I will also add that as described in the Allpar article gas caps from the factory, at least 71+ caps, are pressure-vacuum caps, not normal vented caps. I have used a few aftermarket caps and they have all been normal vented caps. I even bought a 72+ direct replacement cap off ebay in primer ready for paint and it is just a vented cap, not "pressure-vacuum". This being the case, if you are using an aftermarket vented cap, you theoretically don't need any additional venting system.

 

[Revhendo]

No Mopar cap is "vented." When Ma started installing the emissions vapor control (carbon can etc) the caps varied and were known as "pressure vacuum". These ARE NOT operational vents. They are pressure reliefs

There are ONLY THREE vent strategies over the years, which I've already touched on The last two are really similar

1....Up until the CA cars got evap controls, which started in '70 on some cars, the vent WAS ALWAYS the TEE fitting welded into the filler tube in the trunk

2...For a few years, the "carbon can" evap system had a vapor separator can in the trunk. A vent went clear up front, the 1/4" tube which connected to the carbon can system up front THIS IS the vent

3...Somewhere around 73? The trunk vapor separator was dispensed with, and the separator was incorporated into the top of the tank, resulting in ONLY TWO tank fittings..........the fuel supply on the sender, and the 1/4" fitting to the front. THIS IS the vent

So with reference to gas caps (pressure vacuum, technically negative pressure), looking in parts catalogs, they are listed as "vented" or "non vented". Which do you go with?

 

[67Dart273]

I cannot speak for what is differing terminology. A FACTORY proper cap is not an operational vent. "It might be" that some books call them that. My recollection is that "back in the day" we would look it up, get the cap and if "questionable" would just LOOK at the darn thing AND THEN (LMAO) see if you can blow through the new cap LOL

Any of the PV caps I remember, you can tell by looking, "that is what they are"