My truck is having a carb or fuel system issue that I don't understand (or maybe I do and need confirmation). I rebuilt the carb a few weeks ago. Haven't run the engine much since. Was running OK. Now, it starts roughly, idles a bit rough, and if I rev up the engine and hold the throttle open, fuel starts pouring out of these tubes. It doesn't just seep out, it gushes out.



I thought maybe the float was stuck and the needle valve was full open, so I pulled the top off the carb and had a look. The float was not stuck and it seemed to be operating correctly. I know the height is correct (I carefully adjusted this when I rebuilt the carb). I took out the float and needle valve ***'y, thinking there might be some foreign material embedded in the rubber seat. Here's what I found. Look at the corrosion on these brand-new parts! (sorry for the blurry cell phone camera pic, but you can see what I'm talking about).



Then I looked into the float bowl and saw this:



What the what??? The fuel looks yellow and it smells a bit funky. I've never seen gasoline look like that. Do I have water in my fuel tank? The presence of water might explain the corrosion on the parts of the needle valve ***'y.

 

I wonder if you maybe got a bad dose of gas at a gas fill up? Like maybe the station had a bunch of something else in the tank the pump pulled from? Do you buy gas at the same place? Might ask them if other complaints yet? Looks like you'd have noticed the corrosion when rebuilding the carb. Certain mineral water can do that. I would take a further look in the fuel filter. The place you get gas, does it have underground tanks, is it an older buisness? Back many years ago, Dad would not buy fuel in Louisiana on trips unless he could see the storage tanks above ground.

At minimum, I'd pump out the tank, and load it up with fresh known good gasoline. Might get a new carb filter and inlet needle too, unless I could polish the corrosion off. The tip is viton, it probably will be OK. A siphon hose with hand pump to start the siphon right through the fill tube, collect it in 5 gallon cans.

 

The gas had been in the truck since sometime last fall. I bought it at the same local QT station where I fill up all of my vehicles. Never had an issue with their gas.

I will replace those corroded parts in the carb. I think I have another carb kit in my spares cabinet. I will also empty the fuel tank and dispose of the bad fuel. I'm considering pulling the fuel tank and having it professionally cleaned and sealed. This truck sat unused for a while before I purchased it, and it sat for about three years with me. I really don't know what the inside of the tank looks like.

This carb is an unmolested original unit that I bought off eBay and rebuilt myself using a quality Walker carb kit. It was pristine when I got finished with it. It replaced a "remanufactured" carb that I bought from a major auto parts retailer and could never get to run right.

I'd still like to know what soured the fuel and turned it that color. I've had gasoline go bad from age before, but it never turned cloudy and a weird color like that. This really looks like some kind of contamination.

 

this seems on the extreme side, but ethanol is hydroscopic meaning it attracts moisture. if your tank wasn't full this whole time and maybe your gas cap was loose that could draw in a bit of moisture. still i haven't seen it that bad with year old gas in gas cans or lawn mowers. unless you're buying ethanol free gas you likely have 10% of every gallon you buy as ethanol... i know some places have been testing up to 15% but I'm pretty sure they'd have to disclose that. the only other thoughts i could have is if you e85 in that's obviously up to 85% ethanol or if you have a physical way for water to be making it's way into your tank. maybe a hole in the bed directly over the sending unit and the sending unit gasket is toast? i'd think its way more likely something like that

 

If you hold the float in its place on the ends of its pivot rod, you can start the motor without the top on the carb to get a better look as to why your pumping gas out the top. But it has to be a issue with the float, or the needle and seat.

 

I thought about trying that. I'll have to make sure to have my lovely assistant (wifey) standing by with a fire extinguisher, though! But you're right, the only way I can see for that much fuel to come through the carb is if the needle valve is fully open.

 

I agree with @hav24wheel
When the gas changed approx 8 ? years back, I had trouble with the vitron needle tip seating properly on a Holley 4-bbl on a Dodge 413 engine in an RV.
It was like the newer fuel would petrify the needle tip and it would not seat properly causing flooding at idle.
Seems like it took two years and 3 needles to get a good seating needle.

I would do like mentioned above, and with carb top removed, hold the float pivot down, and have someone fire up the engine. Have extinguisher handy.
Fire it up after siphoning the old mucky fuel out of the tank and purging the fuel lines with known good fuel.

Good luck.

 

I'm not a scientist but I'd guess that whatever is in the fuel, most likely water the buoyancy has changed and it's allowing the floats hang open.

On the subject of needle and seats. I learned the hard way thru alot of experimenting that the needle and seat size can have an impact on the amount of fuel pressure it can handle.