Runs smooth, then sputters, then smooth, then sputters

[DoubleDingo]

It is slowly getting better each time I run it. I will wholeheartedly admit that this is the first time I have had issues with fuel in a vehicle that has sat. Typically I add the motor-purr with some fresh premium and I'm off and running. Even with this incident, the truck hasn't sat for very long after swapping the carburetor. I drove it on the warmer days on a fairly regular basis. The only difference is we got tons of rain on the days it did sit, so the ethanol drew in more water.

I tagged you guys because of the other thread about the member asking if premium fuel was okay to run in his truck. I don't intend for this thread to go the way of that one, that thread has enough information about fuel for all to glean off of, just being open that I have experienced something new with crappy fuel going bad.
@RanchWelder @Ricko1966 @Grit dog

 

[TJ1978]

My mind keeps going back to a fuel starvation issue.

Second this... you're loosing fuel somehow. Clogged filter, fuel lines etc. Also just drive it, could be old fuel as well. Good luck

 

[DoubleDingo]

....could be old fuel as well. Good luck

Not old fuel, bad fuel. Way more condensation from like 300% more precipitation over the winter than other years. This next winter season I will be using HEET in every vehicle no matter what.

 

[Ricko1966]

@DoubleDingo if I suspect water in my fuel I will pull a sample at the carb fuel line,1/2 a cup or so,put it in a clear glass jar and walk away,come back in 1/2 an hour you will probably find a layer of water with gasoline flowing on top. Vented gas caps and non working evap. aggravates this throwing that in in case you are running a vented gas cap and no evap.Also others have mentioned full starvation have you done a volume test?

 

[Grit dog]

Not old fuel, bad fuel. Way more condensation from like 300% more precipitation over the winter than other years. This next winter season I will be using HEET in every vehicle no matter what.

Maybe…
But we get 300% more precipitation than most, Every winter.
Although I tend to agree with you. Beena while since I’ve had a carb/fuel issue. But I tend to be relatively vigilant with any of the seasonal or infrequent use engines around the place.
And using E10 gas is effectively like putting heet in your tank. Same thing except E10 gas would be the equivalent of adding 2 gallons of Heet to your 20 gal tank.
Objectively, back in the day it wasn’t uncommon to have frozen fuel lines in snowmobiles occasionally. They get covered in snow and ice then thaw out then covered again, then it’s snowing when you’re filling it with gas, etc. Far more moisture exposure in a short period of time than basically any other gas tank on something sitting unused or stored.
With the introduction of corn laced fuels that hasn’t happened once, ever, since.

 

[Radiohead]

Since alcohol absorbs water, it's entirely possible to have more water than the alcohol quantity will tolerate.
In my case lately, I'm sure it was a combination of excess condensation and old age. That particular fuel that gakked out the farm truck was a can of non ethanol 91 octane.
Distillates change. There are times I wish I had one of those multi fuel engines the military uses.

Lesson for today, keep your powder dry. And your fuel fresh.

 

[legend57]

I had a similar issue on my '57 Chevy years ago when I had crud in the gas tank. It drove me crazy because it was intermittent. The crud will collect on the sock in the pickup, and then slosh off, end then collect again at random times. I went crazy chasing down ignition and carb ideas. I threw a lot of parts at it until someone told me about the gas tank needing to be flushed.

If you've never dropped the tank, you may consider it and put a new sock/pickup on.

 

[DoubleDingo]

I had a similar issue on my '57 Chevy years ago when I had crud in the gas tank. It drove me crazy because it was intermittent. The crud will collect on the sock in the pickup, and then slosh off, end then collect again at random times. I went crazy chasing down ignition and carb ideas. I threw a lot of parts at it until someone told me about the gas tank needing to be flushed.

If you've never dropped the tank, you may consider it and put a new sock/pickup on.

Thanks. I have considered that. When I do, new hoses will be installed at the same time.

 

[DoubleDingo]

@DoubleDingo if I suspect water in my fuel I will pull a sample at the carb fuel line,1/2 a cup or so,put it in a clear glass jar and walk away,come back in 1/2 an hour you will probably find a layer of water with gasoline flowing on top. Vented gas caps and non working evap. aggravates this throwing that in in case you are running a vented gas cap and no evap.Also others have mentioned full starvation have you done a volume test?

I have not done a volume test. To me, it sounds more like incomplete burn, muffled ignition if you will. You can literally feel it running smooth and stumbling and then it clears up and runs strong like normal. Going down the road there is no stumbling, only low rpm high load, and feathering the throttle clears it up almost instantly. If it was a starvation issue, would it not clear up or run strong? Would it continue to stumble and/or just die if it was a starvation issue? I will be checking the cap and rotor soon just for the fun of it.

 

[DoubleDingo]

Maybe…
But we get 300% more precipitation than most, Every winter.
Although I tend to agree with you. Beena while since I’ve had a carb/fuel issue. But I tend to be relatively vigilant with any of the seasonal or infrequent use engines around the place.
And using E10 gas is effectively like putting heet in your tank. Same thing except E10 gas would be the equivalent of adding 2 gallons of Heet to your 20 gal tank.
Objectively, back in the day it wasn’t uncommon to have frozen fuel lines in snowmobiles occasionally. They get covered in snow and ice then thaw out then covered again, then it’s snowing when you’re filling it with gas, etc. Far more moisture exposure in a short period of time than basically any other gas tank on something sitting unused or stored.
With the introduction of corn laced fuels that hasn’t happened once, ever, since.

True, you live in a rainy area, every single day of the year, and you take the proper precautions. You may have storage buildings/garages to store stuff in as well. All of my stuff gets to sit outside 365. We don't get the amount of precipitation that the PNW does except maybe once every 10-20 years. And the powers that be here in this stupid state add stuff to the fuel no matter what season it is. I think I read an article that they were going to keep the summer blend going into the winter of 2022. I read a lot of articles, so I can't pinpoint it.

In 2010, I didn't own this truck, so I can't attest to what it did back then. I only had fuel injected vehicles during that time. 2010 was the last time we got this much rain here.

Reading your description of E10, I may have misread the information I have read elsewhere about ethanol laced fuel. Everything else I have read states the ethanol attracts water, not displaces it or burns it off like HEET does.

I have driven carbureted vehicles since 1985, and this is the first time I have ever experienced this, and I have lived in areas where it got down into subfreezing temps and got snow and rain. Never any starting or running issues with any vehicle in the fleet. Until 2014, I had never ran any carbureted engine with vortec heads. Since that swap the truck is a cold-hearted B, it won't run right when it's below 50 degrees due to no crossover, and it is a royal pain to drive when it's cold outside until the engine is finally up to operating temperature. I am seriously considering swapping heads back with the crossover, as every carbureted vehicle I ever drove that had factory heads with crossovers, they could be ran in any temperature or weather conditions, and also after sitting.

 

[DoubleDingo]

I had a similar issue on my '57 Chevy years ago when I had crud in the gas tank. It drove me crazy because it was intermittent. The crud will collect on the sock in the pickup, and then slosh off, end then collect again at random times. I went crazy chasing down ignition and carb ideas. I threw a lot of parts at it until someone told me about the gas tank needing to be flushed.

If you've never dropped the tank, you may consider it and put a new sock/pickup on.

Thinking about this, I replaced the fuel pump on my 91 Cherokee last year, and the sock on the pump was nasty looking. I can only imagine what this 1981 sock looks like.

 

[Grit dog]

@DoubleDingo
Yes you many have bad fuel, contaminated fuel, idk.
Sorry, most of my point in my last reply was in reference to your comment about using Heet in the tank.
If all you use is E10, adding heet is useless. Imo.
The E10 will absorb more water by itself.

To your point though the fuel tank sender on a square is basically exposed to the rain and it does hold water on top of it. So it’s possible if the old o ring is dry rotted or any damage or degradation to the tank or sender it could be a direct path for water into the tank.
Totally plausible. I could see evidence of water/rust that looked like it made its way past the O ring on the tank I replaced (it was rusted out, but from mud packed inside the plastic tank guard presumably for many years before we owned it).
Fwiw, I replaced one tank and all fuel hoses and new o rings on both.
Once I had that all done I put a thick coat of fluid film over the whole sender unit etc that is susceptible to moisture.

 

[DoubleDingo]

@DoubleDingo
.......my last reply was in reference to your comment about using Heet in the tank.
If all you use is E10, adding heet is useless. Imo.
The E10 will absorb more water by itself.

To your point though the fuel tank sender on a square is basically exposed to the rain and it does hold water on top of it. So it’s possible if the old o ring is dry rotted or any damage or degradation to the tank or sender it could be a direct path for water into the tank.
Totally plausible. I could see evidence of water/rust that looked like it made its way past the O ring on the tank I replaced (it was rusted out, but from mud packed inside the plastic tank guard presumably for many years before we owned it).
Fwiw, I replaced one tank and all fuel hoses and new o rings on both.
Once I had that all done I put a thick coat of fluid film over the whole sender unit etc that is susceptible to moisture.

I guess I read the HEET information wrong, it appeared to me that is to get rid of water, not attract water. I thought I read anything with ethanol would attract water. I need to go back to their website and reread it. My intention is never add anything in the tank to bring in water to the fuel. You are correct about the gasket, though, it very well could be compromised. Good point, and definitely an item to replace when the hoses are replaced.

I guess I never thought of the top of the tank of being exposed to the elements perse. Mine sits under the bed sheltered by the floor of the bed, and the factory rake tilts everything towards the front. Something more for me to look at.

 

[DoubleDingo]

I reread the info on the HEET website, and HEET does in fact remove water, granted there isn't too much already in the tank. And there may be in my case. I think you may have mis-typed what I have quoted in red in my previous post. I did see something linked from the HEET website that says to add rubbing alcohol to the tank to remove water. "Add rubbing alcohol to contaminated fuel, which helps absorb the water and settle at the bottom of the gas tank. Since rubbing alcohol is combustible, it will pass through to the engine without turning into extra residue." Going to try that next before topping off again with fresh 93.

 

[Grit dog]

Ok. But they’re all alcohol and all are water soluble. None “remove” water. There’s no chemical reaction taking place and it can’t just disappear.
Each type of alcohol has a different saturation point and the amount of water absorbed by volume differs.
But E10 will absorb more water than a bottle or 2 of heet in a tank of gas.