VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 varnish in fuel tank

I have a 1951 Chevy Styleline Deluxe 2 dr with a 235".

Due to illness ( mine ), this car has not moved in 2 years. I always used Stabli in the fall, but was not able to do so, in the fall of 2005, when illness struck.

I'm now OK, need to make my '51" ok and soon.

How do I handle this varnish and bad gas stuff?

Thanks, Bob

Bobg51chevy--If your tank was in good shape 2 yrs ago the varnish problem will be at a minimum if the tank was full. Simply drain the old fuel out-refuel use new filter. Give it a try. You may have to replace several filters. There may be other suggestions.

You may also have to clean out your carburetor as it could be contaminated by debris in the float bowl and jetting caused by the foul gasoline that has been sitting in the carburetor.

:) :grin:

n2chev,

The gas tank was fine two years ago ....have a transparent inline filter which always showed a clean flow, showed nothing being trapped in the filter.

I'm hoping your suggestion works, would be happy to replace several filters, if needed.

The tank is in good condition, would not want to take it out and get it professionally cleaned, if it wasn't necessary.

Thank for your input to this new "chatter" guy.

bobg1951chevy

I would suggest draining the tank and flushing it out with some fresh gas. Perhaps pour in a quart and see how it looks when you drain it out. Does the present gas have a varnish smell to it? If it does its a good indication that the gas has gone "bad".
Most gas will last at least one year (thats what I have found with the 10% ethanol we have here) and two will be borderline.
Thats the reason I never fill my tanks before winter storage. You never know what can happen (to an older guy) during the long winter and 16 gallons is a lot of old gas to dispose of.

OK, Chev Nut, I know all about this older guy stuff, but you're right. Too much fuel left in the car isn't good,unless you're on the road.

It does have the smell of gas gone bad.

I am having the carb and fuel pump gone through by a VCCA carb guy, is there a way to flush out the fuel line?

Thanks for your input Chev Nut, looking at your ptofile tells me you've been with VCCA a long time. Good going!

It's like my fiancees social security number .... it is #4, what does that say?

Thanks,
bob1951chevy

After you drain out the old gasoline put in a gallon of fresh gasoline with a pint of B-12 Chemtool (pour can) and let it sit overnight then drain it out into a bucket up at the line that goes into the fuel pump, that should clean the tank botton and the fuel line, and then fill the tank. I just let the line hang down and squirt a couple of squirts of compressed air into the tank thru a air blow gun with a red rag wrapped around it to help seal it at the tank filler, that should get the gas flowing out, it only takes a squirt or two, just don't go whole hog and pressure up the tank a bunch. You may consider adding a pint of B-12 Chemtool to the next tank full of gasoline, it will help clean the carb as you drive.
Some guys say that I don' go to a lot trouble (pulling the tank and replaceing the old fuel lines with new Stainless Steel) and should take the car to a pro, but I am not over run with bat hides, or frog skins, whatever you want to call dollars, and have a lot of time, so I do every Cheap things that I can do to keep from breaking down on the road, having a car towed is something I can't afford, unless I have to.

Mr Mack,

Thanks for your reply. I, like you, am retired and don't have the frog skins to throw around, if I don't need to .....NEED being the key word.

No, I don't fix things by tying them up with coat hanger wire, but do try to watch how many frog skins are going out to fix the ole '51'.

I am now living in Ga, was in Ohio, but am not familiar with the B-12 Chemtool you speak of. Where can it be purchased?

Another though here ...when it became obvious I had a bad fuel problem, I added several gallons ( 2 or 3 ) of fresh fuel which did not help.

However, it did tell me my fuel gauge was no longer working properly, which it had been. It worked well, now it barely comes off empty, regardless of the fuel amount in tank. Do you believe the fuel going bad ( varnishing ) could affect the operation of the tank unit? Could the varnish bind up the float lever?

As I said, the gauge does try to move and does move, just off empty, about the width of the needle.

Any further comments and assistance would be appreciated, I would like to make the ride to the Dahlonega, GA meet in April.

I have been without my '51' for too long, am trying to make up for lost time.

Tomorrow is promised to no one.

Bobg1951Chevy

If the carb was not run dry at the time, then the fuel in the carb would be in the same condition so a tear down and cleaning is in line. Carry a spare filter with you, they have a habit of clogging up in the darndest places.

B-12 is an extremely common product and it is available at any auto parts store either in spray cans or in five gallon buckets.


Since the fuel gauge was working before the varnish developed in your fuel tank, your chances are extremely good that the sending unit is corroded because of the varnished gasoline. If the B-12 doesn't free up the sending unit then you will probably have to drop the tank to remove the sending unit for cleaning.

:) :grin:

The fuel gage float may be bad or even just stuck. I had that happen to the 68 we bought that had been sitting for 4 years. I bought a new gage on ebay but after I drove the car for a few hundred miles and added some premium gas it came un-stuck and works ok now. No I don't fix anything with a coathanger either. I just would rather fix what is wrong than throw money at it.
You can get Berryman's B-12 Chemtool at Walmart, Tractor Supply and other auto parts stores.

When I pulled the tank on my car, there was an obvious layer of varnish covering the entire tank bottom, really thick in the stamped indentions in the tank bottom. The sending unit was coated with the "gummy" residue, including the reostat portion of the unit to the extent that it would not move freely. However, my car had sat for at least 15 years. Hard to believe it would occur in only 2 years. Sounds like your only option is to pull the tank and clean it, and the sending unit. It's not that big a job and you can examine the condition to satisfy yourself. If there's no rust present to require sealing, you can clean it with denatured alcohol. Some of the stronger cleaners, like MEK, can affect the plating on the inside of the tank and actually encourage rusting. They're great if you intend to seal the tank but if the finish is in good condition, they aren't necessary.
The one time I used a fuel stabilizer, the fuel appeared to be contaminated after 18 months and I had to drain the tank to get it all out. Can't say that the additive caused all the problem, maybe I put too much in or there was a existing problem, but I've never used it again.

The original question is ow do I handle this varnish....at this point I would guess that he is only assuming there is varnish which I would also doubt after only two years plus the addition of an additive that helps to reduce varnish formation..

I am thankful for your replies.

I'm thinking it is varnish because of the smell of the fuel. It is rancid, for certain. It's difficult not to recognize the smell of gas gone bad. No, I have no idea regarding the actual presence of any varnish or how much varnish.

I have not taken anything apart, to this point, but wanted ideas as to where to go with this.

One member thought the Stabil, which I had used, could have been responsible for the accelerated accumulation of varish in a shorter period of time.

The other thought is the fuel gauge, which did work, but now doesn't work, as it did. When the key is turned on, the gauge will move the width of the needle off empty. I certainly know there is much more fuel than that in the car now. A member thought the varnish could be responsible for the tank unit sticking.

I'm going to drain the tank, as Mr. Mack suggested, put fresh gas in along with some B12 and see what that brings. I'll also pull the carb, disassemble the carb, see what's in there, as well. The carb is to be rebuilt, just to say it is rebuilt ...as an insurance policy, if you will. I don't ever look forward to sitting on the side of the road with 18 wheelers buzzing 6" beside my butt. The inline fuel filter, which has the clear glass, does not show anything out of the ordinary to the eye.

Any other thoughts would be appreciated.