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Fuel leaking

blue69runner

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Lake Wales Fl.
Ok so have a 69 runner. Put 2 1/2 inch recurve spring's on the back to give the car that rake I wanted. Now have fuel leaking out of on of the vent lines. the short tube in tank. Put a vent check valve on it thinking air could get in and fuel not out. Then after filling the tank and driving noticed have fuel coming out of my frame rail in front of the tire. That is because the long line that goes into the trunk goes to the frame rail. Now my thought is that pressure is building up in the tank forcing the fuel up through that line. Had any one put a vent line on the filler neck to solve this problem. Been a long time but kind of remember doing that with my charger after jacking up the rear end. Any Ideas would be appreciated. Tired of loosing fuel and it leaking from the vent lines. Blue.
 
The vent lines are supposed to let air (pressure) out, not in. The easy solution is to plug both vent lines and replace the non-vented gas cap to one that is vented.
 
The vent lines are supposed to let air (pressure) out, not in. The easy solution is to plug both vent lines and replace the non-vented gas cap to one that is vented.
A vent allows air in and out. You need it both ways. Gas cap is a bad idea. When you accelerate the gas drips out. He needs to fix the vent. Plain and simple.
 
A vent allows air in and out. You need it both ways. Gas cap is a bad idea. When you accelerate the gas drips out. He needs to fix the vent. Plain and simple.
Not true. What I stated was in response to a check valve. The check valve installed the way you said will only allow air in when the pressure differential overcome the spring pressure, and will never allow it to go out at it is against the valve. I have had vented gas caps on, and they don't leak. Just like a radiator cap, they prevent gas to spill out, but when the pressure builds, will allow it to vent when the pressure exceeds the rated amount, and will allow air in when there is a pressure differential also.
 
Lines are hooked up backwards. Short vent line in tank is supposed to go up through the trunk, long line back to filler of tank is supposed to be hooked to the short vent up into the shock mount bulkhead.
 
Not true. What I stated was in response to a check valve. The check valve installed the way you said will only allow air in when the pressure differential overcome the spring pressure, and will never allow it to go out at it is against the valve. I have had vented gas caps on, and they don't leak. Just like a radiator cap, they prevent gas to spill out, but when the pressure builds, will allow it to vent when the pressure exceeds the rated amount, and will allow air in when there is a pressure differential also.
Well you said vent not check valve. The fuel tank needs to expel vapors through the vent as well as draw air in as the fuel is consumed. Its an easy fix with the correct cap and properly set up vent system. When he does it correctly he will not have a fuel leak.
 
@Dennis H had a very custom engineered solution for this, but I can't find the thread.
 
I think it is a capillary effect of hot gasoline with ethanol.
 
Ok the vent lines are correct and hooked to the proper ones on the tank. The vented cap may be the best Idea. Or put a vent on the filler neck. Yes need to let air out and do need air back in. So appreciate all the thought on this. Will take all the ideas to hart and try a few more thing's. Just did not like to see a big puddle under the car and fuel running down the frame rail. No leak to day but did not drive it. May be the fuel moving back and forth in the tank is forcing it out. Plus the heat from the exhaust pipes making pressure in the tank when fuel heat's up. Seems I did have the same problem with a 73 charger and the 69 duster we built to race with. With the tank full the fuel is up to those lines or higher due to the tank is at and extreme angle. Will look for a vented gas cap just don't know who has them and would like locking type. Thanks again guy's. Blue.
 
Ok the vent lines are correct and hooked to the proper ones on the tank. The vented cap may be the best Idea. Or put a vent on the filler neck. Yes need to let air out and do need air back in. So appreciate all the thought on this. Will take all the ideas to hart and try a few more thing's. Just did not like to see a big puddle under the car and fuel running down the frame rail. No leak to day but did not drive it. May be the fuel moving back and forth in the tank is forcing it out. Plus the heat from the exhaust pipes making pressure in the tank when fuel heat's up. Seems I did have the same problem with a 73 charger and the 69 duster we built to race with. With the tank full the fuel is up to those lines or higher due to the tank is at and extreme angle. Will look for a vented gas cap just don't know who has them and would like locking type. Thanks again guy's. Blue.
A vented cap will do nothing for your dilemma. If you do in fact have all the venting in the proper places it should work correctly. Otherwise every 68-70 b-body would be having this issue [Except chargers]. I could see some fuel if filled to the brim and parked on a certain angle. However when you look at the design the vent is higher than the tank so only vapors should be released.
 
I under stand that for sure. Was having a problem with the sending unit pick up tube also and had to bend it to the front of the tank and closer to the bottom. This car is up in the back enough I had to pull down some to hook up the shock's on the shock tower. But the car was empty at the time no back seat and tank was empty. Did not think this would happen. Was getting fuel out of the vent line under the car that looks like a ? and put fuel line on it and put a 5/16 vacuum line check valve on the line to let air in and fuel not to come out. Now the other one that run's up into the trunk and over to the frame rail is leaking. Dam. So now time to figure out how to stop it form doing just that.
 
There lies the problem, you need both lines for pressure/vapour removal. Pressure can't get out your shock mount line because you check valved it, so when the tank pressurizes it pushes fuel out the trunk line. Think of a straw in a sealed bottle.. and you shake or squeeze.
 
I agree. Know I had this problem with a 73 charger and a 69 duster but been a long time sense I had to deal with this problem. What I get for trying to jack up the rear of the car. LOL. But it look's 69-70 ish. Thanks for input. Figured with all the guy's on here might be able to put a nail in the coffin. Think the vented fuel cap is the answer. Maybe or not.
 
A vented cap will do nothing for your dilemma. If you do in fact have all the venting in the proper places it should work correctly. Otherwise every 68-70 b-body would be having this issue [Except chargers]. I could see some fuel if filled to the brim and parked on a certain angle. However when you look at the design the vent is higher than the tank so only vapors should be released.
I believe ever B body with a replacement tank and newer sending unit does have this problem. At least everyone I know has the issue.
 
I believe ever B body with a replacement tank and newer sending unit does have this problem. At least everyone I know has the issue.
Well solve one problem and another one pop's up. Just is frustrating car is finished and drive's well and run's even better. Know you guy's are trying to help and I do appreciate it. It has to be a simple fix but just have not come across it yet. Might be over thinking it like I do some time's. Trying to think out of the box.
 
Simple, you just need the tank designed for 2 1/2" lifted rears...Oh wait ,they don't make one..
Also make sure you now have the correct length shocks. They will top out on bumps if you don't.
 
Simple, you just need the tank designed for 2 1/2" lifted rears...Oh wait ,they don't make one..
Also make sure you now have the correct length shocks. They will top out on bumps if you don't.
Yes I get that no tanks made for lift. The car rides good with it loaded. Did not have to pull the rear down much to attach the shock's. Pulled down on the frame and they connected right up. Monroe shock's standard length. Thanks got a laugh out of tank made for the lift.
 
Ok the vent lines are correct and hooked to the proper ones on the tank. The vented cap may be the best Idea. Or put a vent on the filler neck. Yes need to let air out and do need air back in. So appreciate all the thought on this. Will take all the ideas to hart and try a few more thing's. Just did not like to see a big puddle under the car and fuel running down the frame rail. No leak to day but did not drive it. May be the fuel moving back and forth in the tank is forcing it out. Plus the heat from the exhaust pipes making pressure in the tank when fuel heat's up. Seems I did have the same problem with a 73 charger and the 69 duster we built to race with. With the tank full the fuel is up to those lines or higher due to the tank is at and extreme angle. Will look for a vented gas cap just don't know who has them and would like locking type. Thanks again guy's. Blue.
Fuel tanks fuel cells they are a tough thing as the fuel heats up and sloshes positive pressure as it cools down negative pressure. This is always going to be a tough one. Remember old gas caps were just vented. Didn't matter in or out the trick is just to equalize the pressures to atmospheric. Its all fun and part of learning.
 
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