318 runs smooth then rough. Solved

Hello,

The 318 in my 68 Coronet runs smooth for about 2 minutes then it runs rough and then wants to die. This is when I first start up in the morning.
Started happening last week. Filled up with 89 octane non ethanol
fuel. Drove about 15 miles to my house. Ran fine, no problems. The following day I start up the engine, runs good and smooth for about two minutes then the idle gets ragged and engine wants to die.
318 is stock. Has two barrel carburetor. I'm using electronic ignition.
I check for spark, which I have. Vacuum lines not broken.
Checked output of fuel pump; fuel pumping out good. New fuel filter. With fuel line disconnected I filled a clear bottle with fuel to check for water. At first , it looked like a tiny bit of water at the bottom of the bottle. I dumped out the fuel, cleaned the bottle inside and dried it. Filled bottle again and there was no water. The non-ethanol fuel was gold colored and clear.
It's strange that this happened after I filled up with the non ethanol. It's possible I may have gotten a bad batch of non-ethanol.
The fuel came from WAWA.
Looking for input from other members on the board.

count the # of turns to lightly seat the (2) idle mixture screws then remove em & shoot a healthy 2 second blast of brake kleen into each port on the carb base with the thin red straw affixed to the nozzle then return the (2) screws to their original holes/original # of turns out from lightly seated & how many turns out are they? idle speed adequate?

check the choke

Thanks for the replies so far. Forgot to add; I always keep the choke locked open.

I had a similar issue with water in the bowl. It ran fine until driving up-hill. Also can be a float needle not stopping flow, or float set too high.
Do you have a fuel return (to tank) line?

Need more info. Does it run rough from not enough fuel, or to much? Should be easy to tell from exhaust and smell if flooding or running rich.

Sounds like bad fuel to you. It ran fine until you filled with the new fuel. Did you add a can of Dri Gas to the fuel? I would try that.

Just curious, how does that work?

The carb is a Holley 500 cfm. On that carburetor you can push up
the choke lever mechanism and it lets you lock it into the open position if you don't want to use a cable mechanism.

Problem solved. It was a bad batch of fuel.
This morning disconnected fuel line to connect fuel pressure guage.
After I checked pressure, I drained some fuel into a clear, large diameter line and saw some water settling at the bottom of the line.
Tank was nearly empty. Filled tank with fresh fuel and added some dry gas. Ran engine for a while, idle began to pick up and run smoother.
Thanks everyone for the help.

Thanks for the update ! if all problems could be solved this easily.....

Doh! Uh, yeah, I forgot about bad fuel. I've been burned by that one more than once. My father-in-law is having a similar problem with his 64 SS Nova and refuses to believe his 3 yr old gas might be bad and/or have some water in it.

Glad you got that figured out!!!

In case you didn't know:

Never buy gas when a tanker truck is in the station filling the tanks.
Most gas station pickup tubes are set 12" off the bottom of the tank. The water and debris settle to the bottom. Gas station operators have to check and record the debris level at least 1 time a week, its part of the annual requirements checked when the pumps are certified to deliver 1 gallon of gas for each gallon the pump shows. If the debris reaches a certain level, the tanks need to be cleaned.

When the tanker is filling up the tank, the water and debris are mixed up in the tank, and it generally takes about 1/2 hour after the fill up for it to settle back to the bottom, about the same amount of time it takes the guy to pick up the fill hoses, fill out the paper work, and leave.
If you fill up while the tanker truck is filling the tank, the odds of getting bad gas increases 10 fold. Gene

Your correct what you state.
This particular day I saw no truck there. Maybe it was there the night before; who knows.
Thinking about it. This WaWa probably has very few customers coming to buy the non ethanol considering it is no where near a boat dock or maybe an area that airboats launch at. So, it's supply probably stays for a while. However, at another place I pickup non ethanol, at a Marathon station is a truck stop right by the Everglades; that place probably sells more non ethanol because of people filling up their boats and airboats.
They sell more and the tank gets serviced more frequently. I've had a time I went there and they were out of non ethanol.
Also, at the Marathon station the tank is not in the ground. It's above the ground and at the rear of the property of the station. The tank is much smaller , maybe 12 ft long and about 5 ft wide.