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SteveSS

This gas tank dilema doesn't makes sense to me

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First of all I know I should drop the tank.

It's those two 1963 Oldsmobiles coupes I bought. One is a Dynamic 88 One is a Super 88. Both with Rocket 394's. I have the blue one running with a gallon gas tank under the hood. New fuel pump rebuild it sounds great. Connected to the gas line no luck. I took and air hose and blew it backwards through the gas line. Good pressure build up, I could hear the tank flexing. If the two are connectd why isn't it getting gas?

The white one I just rebuilt the carb yesterday, going back on tomorrow.

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I once had a Cutlass that would starve for gas, it had a "sock" filter over the pickup line in the gas tank, and trying to pull gas through it sucked it shut, restricting/stopping gas flow...don't know if they used those as early as 1963 though...

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Good possibility. I thought those socks would have dissolved by now. It had a couple of glass gas filters on it. I cleaned them. I would guess anything is possible. There could be a dead squirrel in the tank for all I know. I was surprised the tank was vertical instead of flat.

Oh to have a lift.

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Make sure the tank vents are open. It comes off top right side and goes across to the filler neck.

FWIW my blue Starfire does the same thing. It's on the back burner along with everything else. It's one of those "round tuit" things.

Oh to have more than just a weekend off.

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You know, Glenn, I thought that, too. I don't think you should be building pressure by blowing air into the tank. That is a vented system. Any air you blow into the tank should be escaping through the vent. Sounds like it's blocked. If it is, I would imagine that would affect fuel delivery?

Paul

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Okay, if it goes out to the filler neck I may be blocking that off too. I had m son with the air chuck blowing backwards thru the line. I could hear air coming out of the gas tank neck. Whe I put my hand over the neck opening that's when the tank went thunk thunk. Flexing under pressure. I guess I was blocking both the air from the pickup AND from the vent.

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Since I see no mention of the original fuel line from the tank to the steel line being replaced I'll suggest the problem is an old fuel line that has developed a flap inside that is in effect closing the line with fuel pump suction. Not a lot of fun to replace because of the vertical mounting of the tank and having to work around the axle.

Edited by Jim_Edwards (see edit history)

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Had the same problem with a brand new 61 on a trip from L.A. to Colorado Springs.

Albuquerque N.M. dealer removed it and problem solved. Besides why is a sock needed ???

The glass fuel bowl should catch anything that might come through the line.

I have removed the socks on all my early olds and never had a problem.

Good Luck, Dave

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Had the same problem with a brand new 61 on a trip from L.A. to Colorado Springs.

Albuquerque N.M. dealer removed it and problem solved. Besides why is a sock needed ???

The glass fuel bowl should catch anything that might come through the line.

I have removed the socks on all my early olds and never had a problem.

Good Luck, Dave

WOW you are in Colorado Springs? Me too. I am off Baptist Road by the USAFA. I would love to see your cars and have you look at mine. Let me know what I've got.

Nexlevelinc@msn.com

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Had the same problem with a brand new 61 on a trip from L.A. to Colorado Springs.

Albuquerque N.M. dealer removed it and problem solved. Besides why is a sock needed ???

The glass fuel bowl should catch anything that might come through the line.

I have removed the socks on all my early olds and never had a problem.

Good Luck, Dave

The sock keeps rust particles and any other large enough items that may have gotten into the tank from being sucked up into the fuel system. You wouldn't want that stuff stuck in your fuel pump would you?

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The sock keeps rust particles and any other large enough items that may have gotten into the tank from being sucked up into the fuel system. You wouldn't want that stuff stuck in your fuel pump would you?

These cars have been sitting for decades in a metal pole barn. I have fuel filters before and after the pump. They are both '63s but the fuel pump looks different on the two cars. I suspect the white one has a '62 engine. I just don't know enough about Oldsmobiles.

Still if the sock has crapped up or even been sucked into the gas line why would the air pressure pushing backwards work so well as to flex the metal tank when I have my hand over the filler neck and and an assistant push air backwards through the gas lines from under the hood?

I know I know I'll drop the tank it's just hard to get the car high enough to drop a vertical tank.

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In reading this thread the thought hit me that it could be as simple as having the wrong gas cap? If a non-vented cap is on, it will create the same condition you did putting your hand over the filler neck.

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In reading this thread the thought hit me that it could be as simple as having the wrong gas cap? If a non-vented cap is on, it will create the same condition you did putting your hand over the filler neck.

It's backwards pressure when I get the tank to flex. I am blowing air from the metal line under the hood to the tank. By putting my hand over the gas filler neck I can hear the tank flex with pressure. Now, I wonder if the gas pickup line in the tank has coroded off leaving the line to the tank intact but not reaching down far enough to suck up the gas in the tank.

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First, the sock is there for protection. If it's not there a foreign particle can completely cut off the tube pickup, where as on a sock it will not unless the whole tanks jelled up, and GM saw no reason to use a fuel filter before the pump if the sock is there doing it's job. If you blow through the line from the engine compartment you should be able to hear the air bubbling up from the gasoline in the tank. If you put your hand over the filler neck and the tank becomes pressurized the vent for the tank is blocked. Vented gas tank gas caps have no relief built into them like non vented systems do. That means a vented cap does just what your hand is doing blocking the tank neck completely. Non vented systems have no vent tube and the cap will let outside air in to displace the used up fuel ...but those caps are a one way valve as they let in air, but do not let air out and this is the escaping air you hear on a new car ( Post 1969) when you remove the cap when you go to fill up.

With your system you should be able to leave your gas cap on and be able to blow air ( 5-8 PSI) through the gas line from the pump, but remember the tank vent is only a small tube and hose and can be misdiagnosed by putting too much air pressure (125) from the fuel pump end and overwhelming the small tube and pressurizing the the tank.

So make sure your vent system is venting.

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My 20 year old son came home from college last weekend. I'm out of town. Tired of my inaction with the car he stayed up late Friday night bleeding the brakes and rigging up a gas tank under the hood. He had his 22 year old sister helped take the hood off. He got it to drive around the block Saturday afternoon.

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