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Discussion Starter · #21 ·
If you aren't in any danger of needing this truck for a daily driver, wait through the winter and see if it quits. Allegedly, gas formulas change and the colder weather will knock stagnant heat down quickly. See if it quits then.

Not sure what you mean about winter gas formulations and stagnant heat, but with the switch to winter gas, they blend in even more butane (the largest contributor to vapor lock) since temps are cooler they can get away with it. (Butane is plentiful and inexpensive.) So on an exceptionally warm winter day with winter gas, you have the same problem. It's REALLY bad when you have a full tank of winter gas when summer comes around. Some blends (depending on what state and county you buy gas) of winter gas will boil at as low as 100°F. If it's a cold day, no problem, but if it gets too warm out, well you know.

Generally speaking, large hot cities with pollution problems require gas with higher REID vapor pressure values. This is EPA controlled and it cuts down on your gasoline vapors that leak out and contribute to smog. So if you are outside the city limits, sometimes buying gas in the city will help your problems with vapor lock/percolation. Here is a chart for summer gas, I'm sure you can find winter gas chart if you look. Lower numbers basically mean it wont boil as easy.

https://www.epa.gov/gasoline-standards/gasoline-reid-vapor-pressure#table
so if the summer fuel change over isnt til june theres a good chance i have winter mix in my tank. Very helpful. Thank you.
 

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The heat you get from after shutting off the engine and no radiator fan blowing to get rid of it. Heat soak would have been the appropriate term, my bad.

That stinks winter gas has worse characteristics boiling wise than summer gas. But, a 20 degree day will cool stuff down far quicker than a 90 degree day.

I’ve hat an 88 1500 I changed to a carb a few years ago, never had any boiling or vapor lock problems at all, and I run a mechanical fuel pump as well. Oh, it has the clear plastic filter too, and none of it is routed the best either.
 

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I had a 1967 Rochester Q-jet and it did the same thing as you described.

I removed the little bronze filter in the carburetor inlet and installed a in-line Fuel filter and that fixed it. Those bronze filters in the carburetor inlet wil not pass moisture and will stop up with a little condensation in the fuel system.
Strange. I figured bronze wouldn't absorb water.

One year I forgot to top off the tank in my riding mower and next spring my mower ran a couple of laps and started acting like it was running out of gas. I siphoned the tank but when I pulled the hose off past the fuel filter to let the remainder hit the ground, no fuel ran out past the filter yet the filter looked OK.

I put some "different" gas in the tank and a new filter and mowed for about three hours.

Parked the mower for a couple of weeks. Same thing happened.

To me it looked like the filter media became saturated with water and gas wouldn't pass through it. I also ran into this same issue with two cycle fuel. I was using a filter with some kind of foam media and the oil blinded the filter over.

Installed the old filter on the mower, strained all my fuel through one of those Mr. Funnels that removes water and have had no issues since. Since then I always top my tank off in my mowers before putting them up for the season.

I was running 100% gas BTW.

Sometimes I wonder if E10 is actually beneficial when it comes to water in the tank. Where water and gas won't mix so any condensation just sinks to the bottom where lf there is water in the tank, it will attach to ethanol and burn off and sink to the bottom.

The engine may not run very well but water won't burn at all. That's supposed to be the theory behind adding "Dry gas" or "Heet".

I've wondered if that stuff that is supposed to prevent "phase separation" like BG and Stabil actually works or is it just snake oil. By adding this stuff is supposed to allow the ethanol/water and gas to mix.

I never buy new gas for my riding mowers. Any old fuel I drain out of my cars get's strained using my Mr. Funnel and poured into my lawnmowers. I've never had an issue otherwise running junk fuel in riding mower.
 

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so if the summer fuel change over isnt til june theres a good chance i have winter mix in my tank. Very helpful. Thank you.
I was running winter gas in my Ford when this vapor lock incident happened in May 2003.

I *think* the gas I had in my Ford the other day when this happened was purchased in October.

Yes I realize that's considered "old gas".

Dad use to have a 76 Chevy pickup 454 big block. It was actually setup to run leaded fuel.

This thing never vapor locked but experienced developed "run-on" in the late 1980s. About the time they started to phase out leaded fuel. After a few years the problem went away. I guess gasoline got better as time went on.
 
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