Gas Problem? Ideas? See video. Please help.

PepeLoco

PepeLoco

Senior Member
What is going on? Got frustrated with what I thought was vapor lock. Come to a light, stop, then try to leave and it's starving for fuel hesitating or dying. When you look you see the inline gas filter empty. Prior to this I would notice air bubbles popping into the gas filter until all the gas was out. Then sometimes it would not fill back up and it would run really rough or die.

So I:
Pulled tank, no obstruction
Acid washed it in/out
Put in tank Screen filter and Electric valve
Clear temporary hose to see what's going on.
Removed inline filter
Gas cap has been off during these test runs
Temp readings on the carb were around 150, +/- 5 degrees f.
Day temp was around 100. Radiator around 150.

Reminds me of how you can hold a full beer bottle, upside down in a glass of beer.

I am thinking of installing a smaller diameter hose to act as a vent.
Is there suppose to be a vent on the top of the carb to the outside? the only one I saw from the inside top was a pin hole going to the fuel inlet. Nope, I did not check to see if that thing was open or plugged. Rats, may have to do that. Would that be the cause?

http://s1229.photobucket.com/albums/ee466/ChrisNoak/?action=view&current=Gasprobs.mp4
 
What you are "seeing" in the filter is not air; it is gasoline vapor, which looks the same as air. This is what vapor lock looks like. I have seen the same thing, except for me when the filter filled with vapor the flow would stop completely and motor would die. There is no way that air could make it down from the gas tank to the filter--and only do so on warm days!

There is a vent on the carb fuel bowl but it's not easy to see. The problem is that surface tension and insufficient fuel pressure from above is keeping the vapor bubble from getting that far. Some folks who have not seen this with their own eyes insist that it is not possible, so discussions can get a bit testy.

IMO, the first thing to try is simply remove the filter. For some, this is sufficient. For others, insulating the fuel line, crafting heat shields (I see you've already grasped at that straw), or changing carburetors has been required to avoid problems from vaporization in the sediment bowl, fuel line, and/or carb. Some folks report success by avoiding ethanolated gasoline, or by adding Marvel Mystery Oil or a guart or two of diesel/tank to the fuel, or by adding an electric fuel pump (preferably in a cool place). The dumbest thing I've seen reported to work is clipping a bunch of wooden clothes pins to the fuel line, as an alleged heat sink (!?).

Here's a photo of vapor bubble forming in my sediment bowl. It would periodically grow, run down the line, grow again, and again ..., without the running engine barely hiccuping.

4vaporbubblecoversscreen.jpg


Your video is much more compelling! Nice work!

Steve
 
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First I would get rid of that carb, & that piece of metal just below intake.. Put on a GOOD Zenith with a copper gasket.. Next get rid of all the other stuff you just added..
 
Fred said:
First I would get rid of that carb, & that piece of metal just below intake.. Put on a GOOD Zenith with a copper gasket.. Next get rid of all the other stuff you just added..
Click to expand...

After I added that other stuff, I brought the carb temp down, a little and the performance improved (ironically). That heat shield really works. I have a Zenith and can try swapping them out. But it drives me crazy to figure out the root cause.

I appreciate the advice. Hey, what is the difference between a Zenith and a Tilly carb?
 
J Franklin said:
It's time to adjust those valve clearances. An ice bag on the carb would do wonders.
Click to expand...

I know. Need to adjust them as soon as I get this dang fuel prob in check. Otherwise I don't venture too far.

Ice bag? Seriously?
I did think of a saline drip bag from my past surgery, with the line running to the carb!!!!!!!!!

But you know what. I will take you up on that, I will do exactly that. Get an ice bag, strap it to the carb, drive till hot and shot the next vid.
 
J Franklin said:
It's time to adjust those valve clearances. An ice bag on the carb would do wonders.
Click to expand...

steve s said:
What you are "seeing" in the filter is not air; it is gasoline vapor, which looks the same as air. This is what vapor lock looks like. I have seen the same thing, except for me when the filter filled with vapor the flow would stop completely and motor would die. There is no way that air could make it down from the gas tank to the filter--and only do so on warm days!

Ok Steve, how about this?
On the Aquarium fuel line, right at the carb, insert a "T" facing up with a hose running up above the fuel tank; keeping it about the fuel line.

Don't you think it should act as a vent tube and allow all the gas to flow unrestricted?

I even though of brazing a fitting at the tank to have this tube go back into the tank.

Your thoughts?
Click to expand...
 
PepeLoco said:
steve s said:
What you are "seeing" in the filter is not air; it is gasoline vapor, which looks the same as air. This is what vapor lock looks like. I have seen the same thing, except for me when the filter filled with vapor the flow would stop completely and motor would die. There is no way that air could make it down from the gas tank to the filter--and only do so on warm days!

Ok Steve, how about this?
On the Aquarium fuel line, right at the carb, insert a "T" facing up with a hose running up above the fuel tank; keeping it about the fuel line.

Don't you think it should act as a vent tube and allow all the gas to flow unrestricted?

I even though of brazing a fitting at the tank to have this tube go back into the tank.

Your thoughts?
Click to expand...

Thoughts: First, if you don't vent it to the fuel tank I'm not sure how you could get the end of this line above the top level of a full tank of gas without removing the hood--remember, it's going to fill up with liquid gasoline most of the time. Second, it sounds really scary--an open line venting gasoline liquid and sometimes fumes over the top of a hot motor. Third, you're a bold man considering tapping into the fuel tank. Fourth: not sure it would work anyhow--it looked like most of the vaporization was going on in the upper fuel line, which would be unaffected by the mod--also, I'm not sure but it looks like the carb may be dealing with the vapor ok, once it gets down there.

Steve
Click to expand...
 
oldredford said:
The crap in the bottom of the glass bowl is ethanol water mixed fuel. Try pure gas. It happened to me....
Click to expand...

That may have been a bad picture. Here's a better one. Except for the vapor bubble in the top, the rest of the bowl was filled with a homogeneous clear liquid that looked exactly like gasoline.

post2007MARCrepairs043.jpg
 
pepeloco said:
after i added that other stuff, i brought the carb temp down, a little and the performance improved (ironically). That heat shield really works. I have a zenith and can try swapping them out. But it drives me crazy to figure out the root cause.

I appreciate the advice. Hey, what is the difference between a zenith and a tilly carb?
Click to expand...
answer: Your problems !!:d:d
 
Two suggestions:
1. Check how far the gas line extends past the farrel into the carb. This should only be a short amount, if to far the gas line will butt up against the filter in the carb and restrict your gas flow. You might first simply remove the filter in the carb and see if this helps.
2. Try about 4 oz Marvel Mystrey oil in a tank of gas. I always add it for a fill up. Drove back from Oshkosh in 95-100 degree temps across IL, IN, OH, and PA thru the mountains in western PA with no problems.
 
I just got this email today from a RockFord A's Club member I know. It is about one of the few gas stations around the area that don't have alcohol in their gasoline. :(

"I just gassed up at my neighborhood Beloit, WI station. The owners informed me that their distributor gave them manditory rules that their mid-price had to be now 10% ethynol by "law". That soon they will be forced to go to 20%. They had to change the labels on their pumps over the weekend. The low and Hi price are still regular gas.
They are very mad about this political change."
 
The price of gasoline is going up. They can not meet the EPA mandates for ethanol because the drought has caused a big corn shortage. I guess we are going to import corn to make ethanol. Only the government bureaucrats and politicians can be this stupid.

Are you sure you have a vented gas cap? Some people switch them during the polishing process. Nice looking engine. I enjoyed the movie.
 
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