Fuel and oil seperation

[Brian Rupnow]

The i.c. engines I build run on Coleman fuel (white gas) and have Viton o-rings on the pistons instead of cast iron rings. To provide some lubrication for the Viton rings, I add a small percentage of two cycle engine oil to the Coleman fuel. This works very well. Since my carburetors are all of the venturi/no float variety, the top of the gas tank must set lower than the center of the carburetor to avoid flooding and draining the fuel tank. This always results in the fuel line configuration you see in this picture. I have found that when one of these engines have been ran, then left to set for a week or so, the oil separates from the Coleman fuel and collects in a rather "jellied" mass at the low point in the fuel line. This means that the fuel line must be pulled off the carburetor and the "jellied mass" of oil squeezed out of the line before the fuel will flow freely and let the engine start when the fuel line is reconnected to the carburetor. Since I don't have this issue with my chainsaw or weed whacker, which run on pump gasoline and two cycle engine oil, I wonder if this occurrence is particular to Coleman fuel. Has anyone else experienced this?---Brian

 

[canadianhorsepower]

Hi Brian,
My opinion on this would be that Coleman fuel consist of aproximately 30% of crude oil (way more then gas)
and crude oil have parafin in it. With the absence of air ( the sort of Ptrap form by your hose) the parafin tend to
fermentate and produce glucose (sugar) that is reacting to the two stroke oil. Many Ford guys with diesel fuel
had this issue. They were putting 2 stroke oil in their diesel to have more lubricant. They ended out with clog fuel filters
and coroded injector pump

cheers
Luc

 

[WOB]

Replace the blue silicone fuel line with gasoline rated fuel line from the hardware or auto parts store. Gas (Coleman fuel is essentially the same thing) attacks silicone and turns it to jelly.

WOB

 

[canadianhorsepower]

. Gas (Coleman fuel is essentially the same thing)
WOB

FYI
( Coleman fuel is a mixture of cyclohexane, nonane, octane, heptane, and pentane.Though Coleman fuel has an octane rating of 50 to 55 and a flammability similar to gasoline, it has none of the additives found in modern gasoline and cannot be used as a substitute for gasoline, kerosene or diesel fuel in modern engines.Its high combustion temperature and lack of octane boosting additives like tetraethyllead will destroy engine valves and its low octane rating would produce knocking. However, it is quite popular as a fuel for model engines, where the low octane rating is not a problem, additives are unwanted, and the clean burning, low odor and longer shelf life are considered advantages )

and 2 stroke oil is almost 100% additive, and does cause the reaction
"
Additive ingredients[edit]

Additives for 2-stroke oils fall into several general categories: Detergent/Dispersants, Antiwear agents, Biodegradability components, and antioxidants.(Zinc compounds "

 

[Brian Rupnow]

A couple of folks on another forum are telling me silicone tubing is not compatible with gasoline and that is the cause of my problems. They even provided a chart to show that. They may very well be right. I don't know if the tubing I am using is silicone based or not. I will have to try a different type of hose and see. My fuel is mixed and stored in a plastic bottle, and I see no signs of separation there.

 

[canadianhorsepower]

Hi Brian

it could be wrigh also, but I asways use TYCO brand gas line on all my 2& 4 strokes gas engine and
never had a problem

good luck
Luc

 

[tornitore45]

When I built my first engine I did not want to commit to fuel type, Alcohol, gasoline or Coleman therefore I bought a fuel line tube from McMaster rated for Gas and Alcohol (no Coleman rating) that tube is very pliable and the exact same blue color of Brian picture.

I had not had the engine long enough to experience the problem.

If the additives in 2 cycle oil are the problem perhaps we should use a straight SAE 30 non detergent.

 

[Brian Rupnow]

Today I went over to the model store where I purchased the fuel line in the picture, and sure enough, it is silicone. I purchased a length of Tygon the same diameter. I will change the line on my engine today, run it for a while, and let you know sometime next week if that fixes the gelling problem.

 

[canadianhorsepower]

Tygon .

Thats what I wanted to type and not TYCO:fan:

cheers

 

[Brian Rupnow]

--I really don't know for sure what is happening, other than the fact that I have what appears to be a jelly like mass in the low part of the line which won't let fuel flow. I don't know if it is a reaction between the fuel and the tubing, a reaction between the oil and the tubing, or if somehow all the Naptha is disappearing and just leaving the 2 cycle oil undiluted in the tubing. Today I removed the silicone line and put a Tygon line on it, filled the gas tank, and the engine still wouldn't start. Close inspection showed that the fuel in the tank was not flowing into the new semi transparent line. I had to take the top of the gas tank, wrap my ugly mug around it and blow to get the fuel to flow and fill the line.--Then the engine started fine. I have checked the tank carefully to see if the naptha could be leaking out around a bad solder joint, but the outside of the tank is totally dry. I have a 1/32" breather hole in the cap, but I doubt very much that the Naptha is evaporating away through that hole. This is a strange mystery, which I will pursue.---Brian

 

[Rustkolector]

Brian,
The silicone fuel line is your problem, as others have suggested. It isn't compatible with petro based fuels. The yellow Tygon fuel line you picked up at the hobby store is the correct hose for gasoline. I would also suggest that you try a much lighter weight oil in your fuel mix. Most 2 cycle oil is too heavy for a lightly loaded (or unloaded) model engine use. It was designed for very hard working 2 stroke engines. Lighter oils like Marvel Mystery oil work fine at 60:1 ratio for model engines with iron piston rings so it (or other light mineral oil) should work well with your O-rings.

Jeff

 

[Brian Rupnow]

So--after setting overnight with the new Tygon fuel line, The engine started right up with no problem this morning. I will try it again in 24 hours and give a report.

 

[Brian Rupnow]

Started engine again today on same tank of gas, no problems. Engine started right up and I let it run for about 10 minutes. As engine runs more and more, it will idle slower and slower. Right now it's low rpm threshold is about 690 rpm. Any lower and it stumbles badly and stalls. I may eventually try a different carburetor on this engine, as I can tell my Chuck Fellows carb is still allowing some fuel to flow even with the needle screw tightened all the way. That's not a fault of the carburetor design, rather my fault in the way I machined/soldered it. I would hope that perhaps with a different carburetor to get the rpm's down to about 400.---Brian

 

[Brian Rupnow]

Engine started and ran fine today. I think the Tygon fuel line has solved my problem. Will start engine for two more consecutive days, then discontinue this thread. There is no visible "gelling' of fuel happening now.---Brian

 

[jschoenly]

Tygon is great stuff. It will harden some over time, but it's pretty cheap to replace once the fuels "change it" over time. I've also make some custom sized tubing with Tygon where i needed/wanted a different size on one end. You can turn a quick mandrel, boiler the tube to soften, slip it on the mandrel and cool in water. Instant stepped tubing.

George Luhrs for his tiny engines would also use the insulation from solid copper wire for tiny fuel lines after carefully removing the wire. Most of this insulation is PVC I think, but I'll have to pull out some of the wire he used and see if I can get a spec for sure.

Good info in this thread. Thanks!

 

[Brian Rupnow]

We can safely put this thread to bed now. I just started the engine with no problems using the same fuel that was put into the tank a week ago. There is no gelling of the fuel at all with the Tygon line.---Brian

 

[jpeter]

I'll add 2 cents worth: I always burn Coleman fuel and try to use silicone tube. Some brands work and some don't. I find though Coleman brand fuel contains some type of contaminate which looks like fine wood shavings. These collect in my tank outlets, valves and carburetor needles. Thus, I always filter Coleman fuel when filling my tanks. I use a filter/funnel I once bought at the camping supplies store for fillings lanterns and stoves.

 

[mcostello]

I use the same type of filter to fill chain saws and weed eaters, saves greatly on maintenance costs.