Topic: Gas Tank Fuel Qty
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
Lifetime MemberModerator
I think the main reason for doing it this way(with the tube thingy) was to keep the fuel level down below the vent, and vapor return lines, so raw fuel sloshage(a new word I just made up) back into the vent lines would be minimized.
Joel Adams
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That sounds good I was wondering if it was fact their is bladders in the tank. I think the most I have put in my 77 was 15 gallons normally I would never let it get that low but we where on a cruise with C5 and C6 they tend to forget we can’t go as far.
What did you think about the extra line for equalizing pressure for the tanks with bladders?
If that line is clogged it cause the collapse of the bladders.
|UPDATED|10/31/2013 1:33:25 PM (AZT)|/UPDATED|
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This is what I read and the issue davo76 had.
The section in the GM Service Manual (76 Supplement) and it would seem that GM knew of at least one condition that would cause the bladder to collapse: (QUOTE) "There is an equalizer pipe on the tank top which connects to a .035" orifice. The purpose of the equalizer hose is to keep pressure from building up between the tank and bladder and COLLAPSING the bladder." (UNQUOTE)
Then they talk about diagnosing the (QUOTE) "condition of running out of fuel or a limited fill condition, 4 to 6 gallons maximum....." (UNQUOTE) and to check for: 1) Collapsed, kinked, or disconnected vapor hoses at the canister at the frame rail from the fuel tank. 3a-c) Check the vent tube and the orifice for blockage....
There is a T-connection on the top of the tank joining the two vents. The "equilizer" vent from between the bladder and the tank wall and the other from inside the bladder where the fuel resides. The tank/fuel vent was ok and allowing fuel to be taken out by the fuel pump and replaced by air thus equalizing tank pressure. BUT the "equalizer orifice" vent was blocked and not passing any air. I cleaned it out as they suggested and some "gummy gunk" came out. So that is probably what caused the bladder to collapse.
