Gas Cap question

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gtgto

gtgto

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My 70 Duster as originally equipped with the Californa Emmisions (N95). At some point before I bought it the gas tank was replaced with a different type. One that does not have the 4 vent tubes connected to it like the original did. The lines were just cut. The breather in the passenger side valve cover is still original but the line that goes to it is just there for show. Since the system is not as intended with missing vent tubes and all should I be using a different type of gas cap? I get some serious vacuum sound when I remove the cap on a warm day especially.
 
Are you sure it's vacuum and not a pressure build? Mine is a California car with one vent line from the carb back to the tank and on hot days the tank builds pressure and exhausts when the factory cap is removed.
Been that way since new.
 
crewchief said:
Are you sure it's vacuum and not a pressure build? Mine is a California car with one vent line from the carb back to the tank and on hot days the tank builds pressure and exhausts when the factory cap is removed.
Been that way since new.
Click to expand...
It could be pressure......It sounds like when you open a vacuum packed container when the cap is removed.
 
What is your intent for the car.
100% stock?
Just want it to run right?
Easy to deal with?( Fewer parts etc)
 
You need to figure out if its pressure or vacuum. If its pulling a vacuum you would likely have some issues with it starving for fuel.
 
Dana67Dart said:
What is your intent for the car.
100% stock?
Just want it to run right?
Easy to deal with?( Fewer parts etc)
Click to expand...
Just to run right at this point. Have been putting things back to original but the gas tank won't be replaced for a while.
 
MoparMike1974 said:
You need to figure out if its pressure or vacuum. If its pulling a vacuum you would likely have some issues with it starving for fuel.
Click to expand...
I have been stuck numerous times in my car for one reason or another. I remember one time when I still had a clear plastic fuel filter on it and she stalled out on me it acted as if it was out of gas but it wasn't. After removing the gas cap and putting it back on the car fired up and I was able to drive it home.
 
Sounds like someone not only cut the vent tube(s), but plugged them up too. All you need is one vent tube at the top of the tank or on the fill pipe. The gas caps are sealed, even on pre-emissons cars, as far as I know. I know my '69 is sealed.
 
Didn't get a chance to take a better look at it today. I have no idea if my gas tank has a vent on the top of the tank. From what I remember the 4 factory vent tubes were just cut, didn't see them plugged. On a California Emissions optioned car where does the 3rd nipple on the breather on the valve cover come from? Does it connect to the extra canister in trunk near the filler tube?
 
Not sure about the 70 Duster Calif car fuel system. My California 73 only has the one vent nipple on the top of the tank (just above the fuel sender). It runs to the canister up front.
 
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