Fuel tank venting??

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Kent mosby

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Remote Mount Rollover Vent Valve

Where do you mount this? Instructions say above the level of the fuel filler. Many pics online show it mounted in the trunk compatment. Fuel vapors into the trunk??? Makes no sense to me. Does anyone have a picture of where you mounted it? Thanks
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We need to know what model year of your car!!!! These were vented with a very effective and simple system up through 69. After 69 and through 71 ish you MAY have had evap controls (CA state) and after 71ish, the evap controls were mandated federally BUT CHANGED along with the fuel filler cap every year or two.

DO NOT under any conditions put this thing in the trunk
 
67Dart273 said:
DO NOT under any conditions put this thing in the trunk
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Could not agree more!

Out of curiosity why do you want to add that as opposed to using the factory venting system?

In 67 for instance the vent line runs from the tank via hard lines to the top of the filler neck. At the gas station the fuel nozzle dispenses fuel below the port in the filler neck and the added fuel pushes air out to atmosphere or the vapor recovery of the gas station. Gas cap is vented so air can get in and out under normal operations.
 
that looks like a one-way valve. Maybe it only allows air into the tank as the fuel is used up; check it out.
I would try to mount it up on the rear cross member between the shocks.
Oh crap, if I had bothered to click on the link,lol.........
This pic shows the valve mounted on the above mentioned crossmember, NOT in the trunk.
But I fail to see that as being higher than the filler.
Nor do I understand why that would be important. Perhaps someone smarter than me will chime in, hang tuff.
Funny thing is; the instructions teach not to put a low-spot in the line, yet the pic clearly shows one.
Furthermore, my Barracuda has a vent line that follows up the side of the fillerpipe and returns into it, a few inches below the top of it. This would be a perfect place to mount that valve..... if it wasn't inside the trunk.
If your car has a vapor canister under the hood, and if you are not using it, this would also be a good place to mount it. Just don't Tee into it, cuz that would defeat the purpose of the valve.
Like has been said; don't put it in the trunk.It will fill up with highly flammable vapor and is a ticking time-bomb.

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Kent mosby said:
73 scamp
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OK so what is different in the car from factory? Have you removed the "carbon can" evap control system? That WAS the vent originally.

You MUST be careful to get "whatever is there" (or whatever you build) ABOVE the fuel so it will not siphon. Originally, there was a 1/4" tube coming from tank up to engine bay beside the main fuel tube. That IS (was) the vent, and originally had an anti-spill valve in the end of that tube.

We need to know what you are changing
 
Sorry for not giving full details. I am replacing the tank and installing an in-tank fuel pump to feed an EFI. The tank vent and the pump vent Y into a single vent line that is supposed to go to this valve.
 
Kent mosby said:
Sorry for not giving full details. I am replacing the tank and installing an in-tank fuel pump to feed an EFI. The tank vent and the pump vent Y into a single vent line that is supposed to go to this valve.
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Is your neck vented now? If so, I would leave this additional vent out and cap the vents on the tank and th pump. I have a 70 with a vented neck, and was told by tanks, inc that should be fine.
 
That valve is designed to allow vapors to escape except in the event of a roll over, then a ball inside it is supposed to close it; however I suspect fuel would probably be coming out your filler should this event occur.

I have done a number of EFI conversions and in fact am doing one now for a friend. I never use those roll over vents, they just do not seem to be useful at least in a Mopar. On my Challenger I have a line that runs from the top of the filler neck (inside the trunk) down through the trunk dumping underneath the car. On my Cuda I have a similar arrangement except that the line runs from the top of the filler neck inside the trunk to the passenger side and then exits through the trunk floor via a bulk head connector.

The bottom line is that your tank needs to be vented with EFI, there are a number of ways to do this to include the stock system, EVAC system, etc. You can even use a vented filler cap and on your Scamp, thats probably what I would do. The down side to the vented caps is fuel vapors are always present and many people do not want this (does pose a potential hazard and your paint doesn't like it). You could take a page from the factory and run a long line underneath the car from side to side ending with that valve if you are intent on using it, but if the line stays under the car and you fill the car (as you normally would), you are probably going to get some gas dripping out because you will have fuel up the filler tube which will push fuel out that vent line.

In some cases, Mopar ran their vent lines all the way to the engine compartment and then up, in others they ran them up inside the passenger side wheel well to get the height and distance they needed to keep fuel from coming out of them. If you run a line up to the cross member on one side (the one the shocks bolt to) and then back to the other side you should be ok but you won't know until you fill it up. Technically, you could run the line up into the trunk and then back down under the car and that would suffice.
 
Frankly what I would do is duplicate the early (69/ earlier) style vent. It was simple, and it WORKED. Here is a diagram right out of one of the service manuals. It has a 1/4" tube welded into near the top end of the filler tube, a tube goes high up against the quarter panel top, and down along the filler tube, through the trunk floor gasket, and the tube then just open ends into the rear frame rail.

A relevent thread

Fuel cap and tank venting

and the early vent system

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I don't understand how and why you would "vent a pump" however..........

Also if you are running a front-to-rear return line from the EFI regulator DO NOT undersize this line. I would run same size as your suction.
 
67Dart273 said:
Frankly what I would do is duplicate the early (69/ earlier) style vent. It was simple, and it WORKED. Here is a diagram right out of one of the service manuals. It has a 1/4" tube welded into near the top end of the filler tube, a tube goes high up against the quarter panel top, and down along the filler tube, through the trunk floor gasket, and the tube then just open ends into the rear frame rail.

A relevent thread

Fuel cap and tank venting

and the early vent system

View attachment 1715479253
Click to expand...

Some 70 Challengers had this exact same system, it is what got me to use the system I have now.
 
Yup. I call it "69/ earlier" but in 70 the only cars (I'm aware of) were those destined for CA sale.
 
Like said if your filler is vented don't use this rollover valve. If it is not mounted above filler cap it will drain gasoline in filler tube all over the ground when you fill tank full. Big fire hazard at service station. Been there done that!
 
Block it off and run a vented cap.
 
yep when I saw where gas was running out I capped it off at tank.
 
You do not need to vent the pump. There is a separate vent on the pump housing and one on the tank. You could probably just use one and cap one but tanksINC gave me the y adapter. I like the idea of placing the vent at the top of the filler tube assembly.

I thought vented caps leak, Or so I was told.

@67Dart273 Does that line just vent to the at the outside frame rail with nothing on it?
 
It originally ends "open ended" inside the frame rail. I suspect that is to help keep mud/ debries/ undercoat, etc out of it. I would not use a vented cap, it is just one more chance to pee all over your paint.
 
70chall440 said:
Technically, you could run the line up into the trunk and then back down under the car and that would suffice.
Click to expand...

Not always. The later systems can be immersed in fuel, and not connected to the vapor tank used in the trunk. The point is this can cause a siphon situation.
 
I decided to loop the other vents and put a fitting on the filler tube. I will use the pre 1969 method and vent back through the filler tube gasket. Any issues with that method, please advise

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As long as that fitting is liquid tight it should be fine. Just run the tube up as high as you can inside the quarter/ fender, then back down along the filler, through the gasket, and open end it under the car. The originals were open ended inside the frame rails. If fuel ever gets up near the cap, it will siphon a little out through the vent. You want a sealed cap.
 
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