I have a 71 demon. I'm original owner. I have had it restored. The shop manual I bought the year I bought the car describes an elaborate(I suppose for the year) fuel vapor saver system. My car never had this. Of that I am certain. So I fill the car and gas runs all over the place. I have found that at the top front of the tank the guys ran a single fuel line that stops right above the exhaust pipe! Obviously needs to be rectified. Any suggestions? I have fueled the car several times andit did not do this until this last time. I always fuel at same pump
Fuel vapor system
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Maybe a picture would help. I for one am terrible at trying to envision something somebody describes.
67Dart273
Well-Known Member
If you had a "left over" 70 chassis IE early 71, "maybe" I don't know. I would lean more towards "you had it." It is important, however, to refer to the exact service manual, as they changed "year to year." I got a ticket (in part) for my non CA car (70 V code RR) which I was driving in CA in the early 70's. The eco Nazis call the shots, LOL
First look at the tank, filler tube, and gas cap
1....Is the filler cap a "pressure vacuum" cap? If so, you "had" the system
2....Inspect the filler tube in the trunk. Is there a 1/4 vent line factory welded into the filler, and doubling back down through the trunk gasket? No? Then you had the system
3.....Inspect the tank underneath. If there is ANY fittings on the tank besides the one for the fuel supply in the sender, you "had" the system
"How to fix"
The problem (you may have) is going to depend on "which tank" you have. Some of the systems had a can separate from the tank, a "liquid vapor separator." Some of these were built INTO the tank
If your tank does NOT have the built in vapor separator, then that vent line WILL siphon if the tank is full enough, and parked in such a way to start a siphon out that line
BEST way is to pull the filler neck out, weld a fitting onto the side, and duplicate the 69/ earlier vent, and plug the second line, or else use it for a "return" line
The early systems were simple........a line welded to the filler. The filler provided a "vacuum break" to prevent siphon. The 1/4" line came up high inside the rear quarter, and doubled back down through the floor...........where it simply ended.........inside the rear frame section
http://i55.tinypic.com/2cmugso.jpg
The 72/ 73 service manuals SEEM to suggest that A bodies do not use a separate vapor separator. But the 70 and 71 service manual shows this, below. Is there any evidence of this? Should have been a place in the trunk where the vapor separator can "was"
First look at the tank, filler tube, and gas cap
1....Is the filler cap a "pressure vacuum" cap? If so, you "had" the system
2....Inspect the filler tube in the trunk. Is there a 1/4 vent line factory welded into the filler, and doubling back down through the trunk gasket? No? Then you had the system
3.....Inspect the tank underneath. If there is ANY fittings on the tank besides the one for the fuel supply in the sender, you "had" the system
"How to fix"
The problem (you may have) is going to depend on "which tank" you have. Some of the systems had a can separate from the tank, a "liquid vapor separator." Some of these were built INTO the tank
If your tank does NOT have the built in vapor separator, then that vent line WILL siphon if the tank is full enough, and parked in such a way to start a siphon out that line
BEST way is to pull the filler neck out, weld a fitting onto the side, and duplicate the 69/ earlier vent, and plug the second line, or else use it for a "return" line
The early systems were simple........a line welded to the filler. The filler provided a "vacuum break" to prevent siphon. The 1/4" line came up high inside the rear quarter, and doubled back down through the floor...........where it simply ended.........inside the rear frame section
http://i55.tinypic.com/2cmugso.jpg
The 72/ 73 service manuals SEEM to suggest that A bodies do not use a separate vapor separator. But the 70 and 71 service manual shows this, below. Is there any evidence of this? Should have been a place in the trunk where the vapor separator can "was"
Thanks 67dart273. I took delivery on this car from the factory. It never had this system. I have had the gas tank off a couple times through the years. The only opening in the tank is a 1/4 " tube from the front of the tank up high. This is the one I was referring to in original post. My filler tube is without openings or fittings. There has always been a solid metal plate in the trunk where the manuals show the canister would be. It seems I could get a long piece of /4"gas line and run a loop high and let it end. Only problem is that it would all be outside the car. Any thoughts?
67Dart273
Well-Known Member
This is truly troubling. The 1/4 line you describe SHOULD cause siphoning / leaking problems when full, because there is nothing "in there" to break a siphon.
Are you saying that this problem "just started?" Or you you had trouble in the past?
I would just come out an "guess" that "it's worth a try."
What I'd do for a try. You can buy pre--made brake tubes up to 5 ft? at parts stores. Run one from the tank fitting, up through the trunk filler gasket, route it (for support and safety) up along the filler tube, clear up as high as you can get in the rear of the fender, and back down, ending back down through the gasket under the car.
I am just going to guess that IF you get the tank full enough "on a hot day" and IF you park in a certain attitude that it will STILL siphon out IE I'd guess front of tank low
You would want to end your vent as HIGH as possible.
Are you saying there was never anything hooked to the tank fitting?
Are you saying that this problem "just started?" Or you you had trouble in the past?
I would just come out an "guess" that "it's worth a try."
What I'd do for a try. You can buy pre--made brake tubes up to 5 ft? at parts stores. Run one from the tank fitting, up through the trunk filler gasket, route it (for support and safety) up along the filler tube, clear up as high as you can get in the rear of the fender, and back down, ending back down through the gasket under the car.
I am just going to guess that IF you get the tank full enough "on a hot day" and IF you park in a certain attitude that it will STILL siphon out IE I'd guess front of tank low
You would want to end your vent as HIGH as possible.
Are you saying there was never anything hooked to the tank fitting?
This has never happened. I wish I knew what was attached to the line coming from the top of the tank, but i just don't. I am still looking through pix from disassembly and no luck so far. What I need to find is a diagram of my car with no fuel vapor system to see how it was. I do have the Chrysler shop manual and still am looking through it. I am attaching a picture, but it keeps downloading upside down. The hose shown ends directly above the shock absorber. It originates at a fitting directly above the fuel gauge assembly, high up the front of the tank.
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