Air temp and gasoline

[fins2nv]

I have had my 1930 Model A coupe for a year now and it runs great. Last week I was cruising around town for awhile and it started losing power and sputtering. I got the car home and pulled the spark plugs. They didn't look all that bad. One had some carbon build-up. I cleaned them and the next day took the car for a short spin and it ran great. A couple days ago the same thing happened. This time I made it home and just let the car sit for a couple days while we went camping. I didn't do anything to it. This morning I took it out and it ran great. We have had a couple of weeks of temperatures in the 90s with high humidity. My question is, can high air temps and humidity cause a problem with the fuel? I read a comment by Tom recently stating that he hasn't had any problems since he started running straight gas. When I first got the Model A, I ran straight gas. A couple months ago a friend of mine, an "expert in all things mechanical" told me that you can run gas with ethanol in the Model A without any problems. So I have been running ethanol fuel this summer (it's cheaper and easier to get). Could the high temps, humidity and ethanol be causing my problem? I should note that when I took the car out this morning the temp was in the upper 60s and the humidity has finally dropped to a low point.

[Mitch//pa]

try loosening the gas cap when it acts up

[fins2nv]

Thanks Mitch, I'll try that if it happens again. I just read the vapor lock for non-believers thread. Very interesting.

[tinkirk]

double check point gap
sounds off but i fought mine for two weeks doing the same thing after going over every think but the points 2-3 times finally figured out problem was in the points
just saying
Good Luck
T

[H. L. Chauvin]

Hi fins2nv,

FWIW:

Might add, in respect for your life, your stalling situation is a safety concern on today's highways ..... today's texting drivers are not at all accustomed to see a "stalled" or very slow moving stalling vehicle in their lanes ..... a 70 mph rear end collision is very deadly.

Maybe consider in addition to above wonderful advice:

a. Runs poorly ...... cleaned plugs ...... afterwards ..... runs great.

b. Runs poorly ...... did not clean plugs, but let sit ...... afterwards, runs great.

c. Fuel ???????? One at a time:

1. Ethanol gas attracts moisture ...... water is heavier than gas ...... possible water in sediment bowl bottom or carburetor bowl bottom ..... 4 ounces of Marvel oil per 10 gallons appears to help for condensation where cool nights and hot days occur; or,

2. Switch to non-ethanol gas ...... everyday cars usually have no problems with ethanol fuel ...... however ..... tons of cash are made every year with intermittent use vehicles with lawn mowers, four (4) wheeler terrain vehicles used only during hunting season, etc., etc. where mechanics have to clean carburetors with soft varnish build-up.

3. Do you have an A-9193-T cylindrical screen filter above your gas shut off valve to filter your fuel?

4. Eighty (80) plus year old gas tanks are like 80+ year old people .... they can turn loose unexpected "stuff" unwillingly, after 80 years, (even in Church), & never know it ...... also a NAPA or WIX paper fuel filter in glass sediment bowl filters the fine gas impurities.

Let us know your progress .... like many on this Forum, we are most concerned for "your" safety ........... rather than just your vehicle stalling.

[BILL WILLIAMSON]

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I think most of these WEIRD things are caused by GAS BOILING in the carb, think about how HOT the carb gets!
If you're PLAGUED with these problems, run MINUS your HOOD for a month & see what happens??---AND REPORT BACK!!!, PLEASE.
Bill W.

[KGBnut]

I agree with Tinkirk, check your points. This is commonly why a previously good running Model A will start to run lousy, especially if you recently replaced the points. It takes a while for the points block on a new set points to wear in and then you have points too close which results in losing power and sputtering.

I see this a lot with new owners that started with a tune up and a fresh set of points.

Good luck,

Ken

[mshmodela]

I suspect it might be common for Model A in hot weather to have issues after a long drive and then to get them started once the engine has stopped. I've measured my zenith at 150F (the bowl) and think that the gas sitting in there at the temp has to be vapor... However, once started the cool fuel from the cowl tank would prevent the vapor...

[H. L. Chauvin]

FWIW: Just one (1) Model A experience.

I'm not saying it cannot happen with minds while practicing VOODOO.

However, after driving an original, stock Model A in 100 degree heat for years with either a Marvel, a Zenith, and/or a Tillotson carburetor, (and even a Model B carburetor), with a steel fuel line, I never experienced a carburetor overheating problem ....... or a so-called fuel boiling problem ....... or the controversial VOODOO vapor lock problem.

Furthermore, I never even heard that such a problem existed in our years and years of driving Model A's in 100+ degree heat in summers with a 110 degree heat index.

I never even heard of Marie LaVeau using clothes pins on a vintage gas engine to get rid of the well known Python Deity trying to strangle a Model A carburetor.

[MAG]

" Could the high temps, humidity and ethanol be causing my problem? " Yes.

I can not speak for other areas of the country but in central Texas when the ambient tempreature reaches 80 degrees the boiling problem with ethanol gasoline begins. We drive our cars year round and during the winter there is no problem with ethanol fuel. Ethanol free gasoline is not available in this area except in aviation and racing fuel. We have been dealing with this problem for ten years. Every additivine, mixture or concoction has been tried including those mentioned in the posts on this board with little or no success. We have learned to live with it.
The only thing we have done that has had any effect has been changing the Fuel Line between the Fuel Bowl and the Carburetor to 5/16 steel. Doing so has diminished the problem considerably but has not eliminated it.

[George Miller]

Originally Posted by MAG

" Could the high temps, humidity and ethanol be causing my problem? " Yes.

I can not speak for other areas of the country but in central Texas when the ambient tempreature reaches 80 degrees the boiling problem with ethanol gasoline begins. We drive our cars year round and during the winter there is no problem with ethanol fuel. Ethanol free gasoline is not available in this area except in aviation and racing fuel. We have been dealing with this problem for ten years. Every additivine, mixture or concoction has been tried including those mentioned in the posts on this board with little or no success. We have learned to live with it.
The only thing we have done that has had any effect has been changing the Fuel Line between the Fuel Bowl and the Carburetor to 5/16 steel. Doing so has diminished the problem considerably but has not eliminated it.

+2 Same problem here NC in 95 degree weather. Manifold heater does not help.

[Tom Wesenberg]

When I was using crap gas I had fuel boiling problems when the air temp got over 85*. It would start when I had to wait at a red light for several seconds, then it would cough and sputter for a couple blocks until the air flow cooled the underhood temps a little. Using a white plastic wire loom over the fuel line did help some, but the real cure was to only use gas without crapahol in it.

[Bob Bidonde]

I do not believe that the problem has anything to do with the type of gasoline. Things affected by heat & could cause the problem are:
> Condenser;
> Vapor lock in gas line;
> Ignition coil internal breakdown;
> Leakage due to faults in hi-voltage plastic parts such as the distributor body & cap, rotor & coil.

If had to guess, the condenser would be at the top of the bad actor list.

[fins2nv]

Thanks for all the good info guys. I had the coupe out twice yesterday cruising around town and no problem. The temperature was in the low 80s and the humidity had dropped considerably. I do run my coupe with the hood sides removed so it should be getting plenty of air. Also, I don't take the car out of town. The fastest I ever drive it is 40 occasionally when I get on the one street with a 40 mph limit. I will keep all this info in mind if and when I have the problem again. I am, however, going back to running pure gas.

[fins2nv]

This afternoon I decided to check out the filter in the fuel sediment bowl. I hadn't looked at it since I got the car a year ago. Lots of chunks of crud came flying out. The filter screen is clogged in some spots and I tried to scrape the stuff off, but it wouldn't budge. The screen seems to be "welded" into the brass nut. I also see there is supposed to be a spring on the petcock and mine didn't have a spring. I cleaned everything up as best I could and put it back together. I thought the car ran fine before, but I did notice it was a little smoother now. I am ordering a new filter, spring and brass nut.

[Mitch//pa]

Originally Posted by fins2nv

This afternoon I decided to check out the filter in the fuel sediment bowl. I hadn't looked at it since I got the car a year ago. Lots of chunks of crud came flying out. The filter screen is clogged in some spots and I tried to scrape the stuff off, but it wouldn't budge. The screen seems to be "welded" into the brass nut. I also see there is supposed to be a spring on the petcock and mine didn't have a spring. I cleaned everything up as best I could and put it back together. I thought the car ran fine before, but I did notice it was a little smoother now. I am ordering a new filter, spring and brass nut.

Good you made a little headway ....
Just for the record as soon as I acquire a car I go through the fluids, complete tune up, and fuel system. I also do a state inspection type safety check.
Then I drive it...
It doesn't take long for piece of mind. We hear of so many on here that acquire an 85 year old car, jump in and drive it without checking anything.. Then they start posting all their issues which could have been avoided.

[fins2nv]

Thanks Mitch. Good advice.

[Tom Wesenberg]

Originally Posted by Mitch//pa

Good you made a little headway ....
Just for the record as soon as I acquire a car I go through the fluids, complete tune up, and fuel system. I also do a state inspection type safety check.
Then I drive it...
It doesn't take long for piece of mind. We hear of so many on here that acquire an 85 year old car, jump in and drive it without checking anything.. Then they start posting all their issues which could have been avoided.

Mitch........are you trying to put tow trucks out of business.

I do the same as Mitch.
The one time I didn't check the differential gear oil when I bought a new car was on my 1962 Corvan I bought in El Paso. I was going to check it when I got home on leave. Well of course the rear end locked up tight exactly half way home, in the middle of Kansas. I was lucky enough to get towed into the Chevy dealership parking lot, where they let me change it. I was also lucky enough to find a good used differential for only $10. I had my tools along, so with the jack and spare tire I supported the van while I dropped the engine and transaxle to do the swap. The dealership knew I only had $50, so they didn't mind me working in the parking lot.