Hot Weather Driving

J

Jonathan Bourne

New member
During my last two outings in hot weather I encountered very rough running in stop and go traffic. From reading the various threads, I am assuming that what has happened is vapor lock.
When the engine runs so rough that I need to pull off the road and shut it down for a while, or open up the carb adjustment to get enough power to move it has to be fuel related.
There must be a way to overcome vapor lock. Suggestions?
 
Jonathan Bourne said:
During my last two outings in hot weather I encountered very rough running in stop and go traffic. From reading the various threads, I am assuming that what has happened is vapor lock.
When the engine runs so rough that I need to pull off the road and shut it down for a while, or open up the carb adjustment to get enough power to move it has to be fuel related.
There must be a way to overcome vapor lock. Suggestions?
Click to expand...

Yep, raise the vapor pressure of the fuel. This can be done in several ways, ...and we have discussed it in many posts. There is some good reading here regarding this.

One thing to note, many folks do not understand the value, --or the purpose of the GAV. Driver's back in the day used this to fine-tune the performance for the situation they were in. If they were using tractor fuel or even kerosene, they compensated for that low quality fuel with the GAV. If they could only get poor quality low octane gasoline (much worse than today) they compensated for it by adjusting the carb & timing. For whatever reason, I find folks today like to "set it and forget it" and that was never the intended purpose. Modern vehicles have computers on board that are constantly changing the timing and fuel mixture as the vehicle is being driven. On an original Model A, we are to be that "onboard computer".
 
As a Model A rookie living in a warm state, I used to be a believer in vapor lock. I found out from you guys that I did not have vapor lock, what I had was a lot of junk throughout my fuel system. I cleaned everything out and my "vapor lock" went away. Now she runs great even in 100 degree weather. It does not sound like you have my junk problem to deal with however. I'm just saying I have joined the no-vapor-lock-in-Model-A's camp! But I'm a rookie, only had a Model A since last spring so please listen to all the others who will jump in on this vapor-lock issue!
 
Joltesvig, come to Minnesota on a hot summer day and use some of the crap gas and you'll soon be a believer again.:mad::eek: It ended for me since I found a station about 6 miles away that sells the good gas.:)
 
I believe some of the problems encountered today have to do with the ethanol in the gas. I had all sort of problems when one day I discovered water gunk at the bottom of my tank. Now my Model A resides in a big garage insulated from the outside envronment. So how did this water gunk get in my tank? Has to be the ethanol crap. I did like Tom Wesenberg does and buy only pure gasoline. I have to pay alittle more but it is worth it. Ever since I started using 93 octane 100 percent pure gasoline, all the water gunk and crap is gone and my Model A runs great. The thing I worry about is that they will outlaw pure gas.
 
Jonathan:
There has been a lot written and many pictures posted on Ford Barn concerning "vapor lock". It is worth your time to do a search.

Brent - you have it wrong on raising the vapor pressure to correct vapor lock. You need to reduce the vapor pressure.

One way - not recommended because of adding to the hydrocarbon pollution is to leave the gas cap open with the tank in the sun. You will boil away the light components in the gasoline and reduce the vapor pressure. What I have found to be a cheap and effective way to improve the driveability is to take some 5/16 rubber hose, slit it lengthwise and cover the fuel line. This will reduce the heat transfer to the fuel.

Vic
 
These ethanol-blended fuels are trouble in non-fuel injected engines.

The other week, I was on the Northeast Turnpike Extension for a ten mile run, on a blazing-hot 90+ deg day.

Had to stop for a toll-booth, there was only one lane open, and a long line, with several camper trailers ahead of me.

The car ('28 Coupe) had been running fine, but after sitting for a few minutes in the toll queue, it began to run rough, bucking and spitting.

I advanced the throttle some and opened the GAV, but it would not idle nicely. The temp gauge was showing between 190 and 200, warmer than when running down the road.

So, I kept the idle up around 800 - 1000 RPM until I got through the toll booth.

Once under way, with good air-flow, after about a mile or so, the car began to run better, and I was able to turn the GAV back in to its normal setting ( 1/2 turn open ).

It has repeated this behavior in similar stop & go situations in very hot weather ( ambient air temps over 90 deg F ).

For my 80-mile run down to Macungie last week, I was thinking about rigging an ice bucket or coffee can with ice around the sediment bowl, but they day started-off reasonably cool, so I figured I needn't bother. The car ran fine.

So far I haven't found "real", unadulterated gasoline around here, so I 've been dealing with the corn-likker.
 
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