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1923 Buick Fuel starvation


southjk
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Well I've run out of things to try on the Stewrt vacuum pump and Marvel carb.

Engine starts and runs fine until fuel is used up in float chamber. When engine dies the gas comes rushing back into the carb. I have completley disassembled the fuel system including the tank. I installed a glass filter so I could see if the fuel is being sucked from the tank and it does. I don't seem to have any vacuum leaks as I've used thread sealer on every connection.

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OK, you are getting closer. The problem is in the tank itself. If the guts are working correctly, the float will lift up as the fuel is sucked in the first smaller tank, and in turn will allow fuel to be released to the second tank and then to the carb. Fuel is not getting from the first tank to the second tank. Check the little flapper on the first/inner tank that releases fuel into the second tank. I just sent you an email with a copy of a SW trouble shooting guide. See page two for a diagram of the guts of the system, make sure you have all the parts, you are missing something internally. You have two tanks, inner and outer right? Worse case post some pictures of the guts so we can see if anything is missing.

Do not despair.

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I do have all of the parts and an inner and outter tank. I checked the little flapper valve..theres not much that can go wrong with it. Everything is moving freely. Fuel is somehow being released when the engine dies. Suction is keeping the flapper closed I geuss. The valve that releases the vacuum must not be working right and allowing gas to flow from the in er to the outter tank. I actually sprayed penetrating oil over the valves and linkages just to make sure they were moving freely..then I sprayed with a solvent to remove the oil resisdue. Everything looks right but something is still wrong..thanks for the stewart pdf file.

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Think I may have found the problem anyway...when I remove the vent tube and manually lift the check valve I can make the fuel transfer from the inner to the outter tank. I think maybe that weak vacuum due to a leak might not allow the proper amount of fuel in the inner tank to raise the float high enough to push up the vent check valve. I resolderd the fuel line into the banjo fitting thinking I may have a leak there. no help. I had new copper crush washers on the banjo connection but I observed fuel around that connection so I'm gonna replace the copper washers with the hard fiber washers and see if that helps the vacuum situation...

Added the new washers and now how good seal at fuel connection. No change in performance ..must have vacuum leak somewhere.....

Found another possible problem. I was checking the tank connection (rear main tank) and thought I'd resolder the tube going into the tank. I noticed the end of the tube had some crud in it.it wasn't totally obstructing flow but may have been clogging where the connection makes that bend at the banjo fitting. When the engine dies it probably fell back down..someone on the thread had mentioned this ...I'll let you know how it turns out.

Edited by southjk (see edit history)
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