KJQ Posted January 29, 2023 Share Posted January 29, 2023 Can't fill my 72 402 with gas without overflow after a few seconds. Tried with a gas can and same results. Thoughts? Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 29, 2023 Share Posted January 29, 2023 On newer, 'emission' controlled cars it's usually because the gas tank vent valve has failed close, thus not giving that displaced air any place to go. A 1972 Monte has a vented gas tank, but not anything like the systems in newer cars, may be worth looking into though. Is it possible something is blocking the filler neck? Critter, rag, sabotage, etc... I'd steer more towards that initially, based on what you're saying, especially with a gas can (less volume and flow than a gas pump, but still overflows). Quote Link to comment Share on other sites More sharing options...
KJQ Posted January 29, 2023 Author Share Posted January 29, 2023 (edited) Is the filler tube supposed to be smooth inside? I have what looks a spring that tapers down. Edited January 29, 2023 by KJQ Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 29, 2023 Share Posted January 29, 2023 Sometimes there are what looks like ribs in there, from the bends/kinks in the tubing. Can you take a picture? Quote Link to comment Share on other sites More sharing options...
KJQ Posted January 29, 2023 Author Share Posted January 29, 2023 Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 29, 2023 Share Posted January 29, 2023 Not something I've seen before. Maybe someone put it in there a long time ago to prevent vandalism? How long have you owned the car, who owned it prior, etc. 1 Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted January 29, 2023 Share Posted January 29, 2023 Remove that and the issue will be fixed. I agree with Joe, I have never seen that before. Quote Link to comment Share on other sites More sharing options...
KJQ Posted January 29, 2023 Author Share Posted January 29, 2023 I've had it 10 years and never had an issue- always garaged. I thought at first it might be from a gas nozzle but IDK. Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 29, 2023 Share Posted January 29, 2023 It may be hard to remove, if the spring is expanded out. May have to twist it backwards, to 'screw' it out. If it's always been in there though, with no trouble...hmmm Quote Link to comment Share on other sites More sharing options...
FrankOC Posted January 29, 2023 Share Posted January 29, 2023 I recall that the springs were a popular anti-siphon measure back in the 70’s. 5 Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 29, 2023 Share Posted January 29, 2023 Just now, FrankOC said: I recall that the springs were a popular anti-siphon measure back in the 70’s. Yeah, the 1974 gas crisis 🤑 1 Quote Link to comment Share on other sites More sharing options...
KJQ Posted January 29, 2023 Author Share Posted January 29, 2023 Was able to remove the spring and put some gas in with the gas can..but then the overflow happened again. 99.9% sure the tank is not full...thoughts? Quote Link to comment Share on other sites More sharing options...
Rob Peters Posted January 29, 2023 Share Posted January 29, 2023 I would have thought removing the anti-siphon spring would have fixed your issue. It seems something has to be blocking the filler neck. Due to it being a gas tank, I'm not sure if a camera can be put down there, without risking a fire, to see if anything else is down there. rob 1 Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 29, 2023 Share Posted January 29, 2023 72's have 3 vents on the tank I think. One on each end, one near the middle. Do you still have the charcoal canister and all the original emissions equipment? If you have access to a borescope, you could look down the neck like Rob is suggesting, but it looks pretty clear. I was figuring a jerk shoved a potato down there, or some 'Great Stuff" expanding foam...good way to immobilize, (especially up a tailpipe with a 3 foot extension tube...stealthy) When I get home later (dinner at gf's parents), I'll put up a picture of the gas tank and fume canister behind the back seat. It's here somewhere if you search though, unless somebody else directs you to it. 1 Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted January 30, 2023 Share Posted January 30, 2023 3 hours ago, KJQ said: Was able to remove the spring and put some gas in with the gas can..but then the overflow happened again. 99.9% sure the tank is not full...thoughts? Silly question, but, Could it be full? The 70 Monte Carlo doesn't have any vents on the tank other than the filler neck with a vented cap. The filler neck for a 71+72 are of the same size and dimension and no obstructions in the neck. Just 2 outboard, 1 on each end of the tank for emissions purposes. 2 Quote Link to comment Share on other sites More sharing options...
jft69z Posted January 30, 2023 Share Posted January 30, 2023 Here are some diagrams of the fuel tank connections. For your 1972, you'll see 3 lines come from the fuel tank going to the vapor separator, then the 'Vapor Pipe' from the separator going up to the front charcoal canister. If someone capped off the one going up to the front, that would effectively block off those 3 vent lines. Would that cause a condition as you're experiencing, I don't know, doubtful... The 1970 appears to have a standalone vent/surge connection on the right side (item # 10), according to factory diagrams. Unless those vent tubes are plugged, and causing the problem, the only other reasonable suspect can be a restriction further down in the filler neck, which is hard to believe considering that spring you removed should have stopped it.  1972 Fuel Tank:   1970 Fuel Tank:  72 vapor canister lines.pdf 70 fuel tank lines.pdf  2 Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted January 30, 2023 Share Posted January 30, 2023 I have noticed when I put gas in mine if the nozzle is at an angle it will sometimes kick off as opposed to if I have it straight up. It usually will kick off also when filling it up before it's completely full, it can take a dollar or two more after clicking off but I only do that if I'm going to use the gas right away(like a trip) because gas does expand especially in the summer due to high temperatures. 1 Quote Link to comment Share on other sites More sharing options...
stangeba Posted January 30, 2023 Share Posted January 30, 2023 Steve Lavoie, You just reminded me of the gas that would run all over the driveway, in the hot summer, from my dad's 62 Pontiac Catalina. I would put a gas can under it to catch the runoff and use that for my mini bike that I made back in 67. GOOD TIMES!! Sorry, off subject.................... Â 5 1 Quote Link to comment Share on other sites More sharing options...
Montemedic Posted January 30, 2023 Share Posted January 30, 2023 That’s awesome Bruce. Creative recycling at its best !!! 1 Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted January 30, 2023 Share Posted January 30, 2023 33 minutes ago, stangeba said: Steve Lavoie, You just reminded me of the gas that would run all over the driveway, in the hot summer, from my dad's 62 Pontiac Catalina. I would put a gas can under it to catch the runoff and use that for my mini bike that I made back in 67. GOOD TIMES!! Sorry, off subject....................  That's not a mini bike that's a Maxie bike 🤣 2 2 Quote Link to comment Share on other sites More sharing options...
Scott S. Posted January 31, 2023 Share Posted January 31, 2023 If you park on a downward slope, the gas flows much easier. Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted February 1, 2023 Share Posted February 1, 2023 On 1/30/2023 at 2:35 PM, stangeba said: Steve Lavoie, You just reminded me of the gas that would run all over the driveway, in the hot summer, from my dad's 62 Pontiac Catalina. I would put a gas can under it to catch the runoff and use that for my mini bike that I made back in 67. GOOD TIMES!! Sorry, off subject....................  And here's how it starts eh Bruce? 🤣🤣🤣 5 3 Quote Link to comment Share on other sites More sharing options...
420ponies Posted March 23, 2023 Share Posted March 23, 2023 That's weird, my '72 doesn't have that extra tube running on the same side as my fuel line. I know I have a non vented cap too. Can't help you on that Quote Link to comment Share on other sites More sharing options...
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