Question for Quadrajet Users - Disapearing Gas from Fuel Bowl

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RWBeringer4x4 said:
Well, 48 hours later, my truck is calling me a liar - After running it up to operating temperature and getting things nice and hot, I shut it down and let it sit for two days. It fired right up and ran again tonight, so there was still gas in the bowl... It has been 96+ degrees around here lately so this is a good time to be testing this stuff...so far, so good. I guess I'll push it out to 3 days next and see if it still starts.
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Hi RWBeringer4x4,
I hope you don't mind me bringing this thread up and asking you if you ever resolved your issues.
I'm not sure if I have the same issue, but my issue is that my V8 with a quadrajet in my 75 FJ40 will hard start occasionally , but after a few days it seems the gremlins have gone away, like yours though it seems like fuel is going some where because don't see it leaking anywhere and it's not in the carb. I don't have a return on mine and I am debating if I should put in a boost pump as Mark suggested.

Thanks!
RobQ
 
Reformulated or oxygenated gas wicks out of the fuel bowl and drips into the manifold. If it has only been a day or two and there is still a gas puddle in the bottom of the manifold, use the flooded engine start drill. Hold the pedal down, don’t pump and hit the key and let up on the pedal when it starts. If it has been a long time and the fuel has evaporated, then crank it for 5 seconds, give the pedal a couple of pumps and then start it.
 
I never figured this out - the same issues have plagued me through two quadrajets so I’ve just learned to live with them.

1. If I’m driving around on a hot day and I park it for a few minutes, the engine floods. I’m guessing the fuel’s percolating out of the bowl when it’s hot and sitting in the manifold like @Pin_Head mentioned.

2. If it sits for more than a day the fuel bowl is bone dry. The common Welch Plug issue is addressed with epoxy so I don’t think it’s leaking down. I don’t notice anything leaking out the jets after I shut it down. All I can figure is that it’s either syphoning back into the fuel tank or modern gas just evaporates really, really fast.

When I haven’t started it recently it takes 5-10 seconds of cranking to get gas back in the bowl, then it fires up like it should. Can’t be good for the starter but I’ve given up trying to fix it.
 
RWBeringer4x4 said:
I never figured this out - the same issues have plagued me through two quadrajets so I’ve just learned to live with them.

1. If I’m driving around on a hot day and I park it for a few minutes, the engine floods. I’m guessing the fuel’s percolating out of the bowl when it’s hot and sitting in the manifold like @Pin_Head mentioned.

2. If it sits for more than a day the fuel bowl is bone dry. The common Welch Plug issue is addressed with epoxy so I don’t think it’s leaking down. I don’t notice anything leaking out the jets after I shut it down. All I can figure is that it’s either syphoning back into the fuel tank or modern gas just evaporates really, really fast.

When I haven’t started it recently it takes 5-10 seconds of cranking to get gas back in the bowl, then it fires up like it should. Can’t be good for the starter but I’ve given up trying to fix it.
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Thanks for the quick response. Sorry to hear you never figured it out. I just thought with some of the stuff for hard starts on the Internet you might have had figured it out and there was a solution since there so many people that use Quadrajets. I just can’t seem to figure out which one to try first. So I guess I will be doing some trial and error stuff first. Starting with what Pin_head suggested.
Thanks,
RobQ
 
There is also a possibility of the carburetor having been soaked too long in carburetor cleaner some time in it's life that has removed the chromate seal from the aluminum body. (search for "porous carburetor")

While this may not be an issue on the QuadraJet, it has been an issue on Carter carbs (Studebaker) and I have personally killed a carb by doing this. As the carbs get older and have been soaked and rebuilt, it removes the surface finish that seals the body of the bowl. Especially with the new oxygenated fuels, the fuel evaporates quickly through the walls of the bowl.

My Stude will barely run on E-10 gas because it vapor locks VERY quickly due to the stock routing of the fuel lines. I will only run non-ethanol gas unless I am in a state that does not carry it. Then I will search out racing gas or aviation gas (yes, you can buy gas for your car at the small airports) but it's not cheap. I have paid over $7/gallon because it is that much of a PITA. I have sat for HOURS waiting for the engine to cool enough to allow fuel back to the carb.

Some have tried epoxy coating the interior of the bowl but it will not hold. You need to consider having the carburetor rebuilt by a rebuilder that can have it re-chromate coated.
 
I think that the surface finish of the carb bowl is an important part of it seeping or wicking out of the carb bowl Due to the higher surface tension of ethanol gas. The rough surface is a better surface for it making its way up the bowl and into the idle circuit. It drips out of the idle port, which is the lowest point that gas reaches on the carb. I was going to try drilling out the idle hole in the bowl casting about 1/4 inch and installing a piece of teflon tube because gas won’t wet the teflon.
 
There are enough Marinas near me that I expect I could probably find some non-E10 gas, but the "Pure Gas" website shows the closest about a half hour away in PA. Might give it a shot at some point but driving 30 minutes every time this gas guzzler needs has isn't a long-term solution. It would be down a quarter tank again by the time I got it home! I've also considered adding a phenolic spacer or an aluminum heat shield between the carburetor and the manifold to keep the carb temperatures down and avoid percolation but never pulled the trigger.

I forgot to mention - The last thing I attempted to do to address the fuel loss issue was to install an anti-drainback valve right at the carburetor that SHOULD prevent fuel from siphoning back to the tank from the fuel bowl - which makes this even more of a mystery. The only way for the fuel to run is forward, into the carb. But after a couple of days of sitting the whole fuel system is bone dry. I'm not even sure there's fuel in the fuel lines. So my only guess is something like what @Pin_Head is talking about. Fuel is syphoning forward into the manifold and pulling the gas out of the fuel lines and into the bowl as it does it, until the siphon-seal is broken.
 
I don’t think that engine heat is a major player in this issue. My carb would seep after filling the bowl and letting it sit on the bench.

Fuel can’t siphon back into the fuel pump and tank because there is an air gap between the inlet check valve and the fuel in the bowl. Fuel can’t’ siphon out of the idle circuit either for the same reason. That leaves only surface tension and wicking or creep as an explanation.
 
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