Vapor lock!

kingbee

kingbee

Senior Member
My first drive in an A in HOT weather in 40 years. (and back then we had good gas) After an hours drive, shut down the engine for a few minutes and it would not restart. Lots of cranking proved frutile. Held the choke out for 20 strokes, nothing, INCLUDING not even a drop of fuel from the carb. Checked the spark & it was strong. 40 minutes later it started. 30 minutes later it died at a stop - same scenario.

My question is not If I had vapor lock, since the spark was good. I searched out all the threads on the barn, and there were mentions of Marvel mystery Oil (among other things) being added to the fuel.

Finally my question - how much should be added per gallon to help eliminate the problem?
 
If vapor lock exists, can someone here convince me why my T has never exhibited any signs of it? This T has been driven in 105 degree weather, has no water pump and is gravity feed with the carburetor right next to the exhaust. I use the same gas as everyone else whether it has corn in it or not. It never fails to start no matter the temperature and is hand crank only.
 
Take heart, kingbee, because some people have not experienced vapor lock, it can't possibly be happening to you! :)
 
i took My 1951 john deere G on a tractor ride yesterday for our tractor club, i made it 20 out of 25 miles until it vapor locked. I let it cool down and put in a couple of table spoons of water in the gas tank and let it idle, when it quit, ( water went into the carb) i cranked it over with the key off for about 5 seconds, it then started right up and never had a problem again. When the water went throught the carburator, it cooled it since it has a higher boiling point and and would not burn, when it was flushed out of the carb and into the manifold it cooled the pistons and valves,
Worked for me, I have since added some oil in the tank.
add about a half a cup for 10 gallons, i ran a cup in 20 gallons
John
 
There seems to be many cures for vapor lock from clothes pins to MMO.. A little kerosene or diesel fuel mixed well with the gas even helps.. But, with fuel prices today the MMO may be cheaper.. Personally I think a heat shield around the exhaust pipe seems to work best..
 
I have experienced this with my 30 Coupe. The problem turned out to be a gas cap that didn't vent properly. On one trip, it started backfiring and quit. After all the common checks, I went to open the gas cap and heard a vacuum sound. It is a reproduction gas cap and it wasn't venting properly. The old original one worked great.
 
Ken, thanks for your suggestion - I checked that, as it's a common problem on the Honda Valkyrie.

Thanks Mike, but I had a good strong spark which I tested, as I knew it could be a possibility...
 
James Rogers said:
If vapor lock exists, can someone here convince me why my T has never exhibited any signs of it? This T has been driven in 105 degree weather, has no water pump and is gravity feed with the carburetor right next to the exhaust. I use the same gas as everyone else whether it has corn in it or not. It never fails to start no matter the temperature and is hand crank only.
Click to expand...

James,

I appreciate your puzzlement. All I can say is that this is kind of a spooky issue. The oddest case I know of is a fellow in our club (Dan/Kzo) who has two A's that NEVER vapor lock and one that ALWAYS does (temps >90 F). Same carbs, engine pans, distributors, gasoline, driving habits, weather, altitude, etc. His story is the 8th one down in this earlier vapor lock thread:

http://www.fordbarn.com/forum/showthread.php?p=214082&highlight=vapor+lock#post214082

Steve
 
I think I understand what Kingbee is referring to.. The Valkyrie doesn't really have a vapor lock issue,, but,, it does have a fuel starvation problem when the fuel tank has been removed and its then easy to pinch the fuel tank vent line and not notice it.. So, I think we are talking about the same thing..
 
Hi Kingbee,

Four (4) ounces of Marvel Mystery Oil to 10 gallons of gasoline will work in answering your final, single question:

"Finally my question - how much should be added per gallon to help eliminate the problem?"
 
If you don't have MMO or diesel at your disposal, shutting the gas valve and running the carburetor dry at a pit stop helps. When you go to leave, open the valve and the carb will refill with cool gasoline from the tank.
 
BrianBurkert said:
If you don't have MMO or diesel at your disposal, shutting the gas valve and running the carburetor dry at a pit stop helps. When you go to leave, open the valve and the carb will refill with cool gasoline from the tank.
Click to expand...

A few years ago I was parked in the hot parking lot of the Twin Cities Ford plant and had ethanol laced crap gas in my tank. I went to start the car after being parked for a few hours and found the gas had boiled the carb dry. When I opened the valve the gas wouldn't start flowing until I opened the fuel line at the carb. When I made another stop that same day for another few hours the exact same thing happened again. Never had that happen with the good gas I've been buying lately.
 
steve s said:
James,

I appreciate your puzzlement. All I can say is that this is kind of a spooky issue. The oddest case I know of is a fellow in our club (Dan/Kzo) who has two A's that NEVER vapor lock and one that ALWAYS does (temps >90 F). Same carbs, engine pans, distributors, gasoline, driving habits, weather, altitude, etc. His story is the 8th one down in this earlier vapor lock thread:

http://www.fordbarn.com/forum/showthread.php?p=214082&highlight=vapor+lock#post214082

Steve
Click to expand...
Steve, I also watched Brent remove not only the fan from his T but the bottom pulley on the same day in the same heat in Minnesota no less. I thought he was nuts and would destroy a motor I had just reconditioned with a Stipe cam and a Scat crank. The car ran great and had no overheating or vapor lock problems. I don't believe in vapor lock because of situations like this. We were using gas with corn in it right from any convenient pump. I don't believe alcohol gives any problems other than the BTU's are lower. This means with lower BTU's engines would run at lower temps.
 
J. Rodgers

So, what reason are you giving for the engine to run rough on hot day's ?

In my case, the engine ran real rough with very little power until I pulled out the choke some. After awhile it ran O.K.

Only happened on real hot days under the conditions I have talked about

If not vapor lock, then what ?

Surely you do not think that because it hasn't hapened to you, then it can't be true.


Marc
 
On the original post I believe your float valve may have stuck. Mine has done the exact same thing before. I personally don't believe in vapor lock not because it has never happened to me but because it is a term thrown around simply when someone doesn't know the problem. The alchohol in fuel boils at around 170 degrees and gasoline boils around 200. I've never seen a car when I cannot lay my hand on the carburetor because it is that hot.
 
marc hildebrant said:
J. Rodgers

So, what reason are you giving for the engine to run rough on hot day's ?

In my case, the engine ran real rough with very little power until I pulled out the choke some. After awhile it ran O.K.

Only happened on real hot days under the conditions I have talked about

If not vapor lock, then what ?

Surely you do not think that because it hasn't hapened to you, then it can't be true.


Marc
Click to expand...
I am a realist, if I see it I might believe it. There are many things heat can affect that will keep a motor from running. Could be a bad condenser, a weak coil, the starter could be pulling too many amps and robbing the distributor, I have even seen the fuel tank expand enough to touch the wires on the ignition switch and short them out till the tank was at half full or the cap was loosened to let out the pressure. When a car sits for a short time after running without the fan to push heat out of confined spaces accumulated heat will affect lots of electrical parts. I don't believe in vapor lock, jkeesey is right, it is easier and sounds better to say vapor lock than "I don't know".
 
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Lets go another direction. Think about a riding lawn tractor that we mow the grass with. Everyone is generally using the same "ethanol-laced" fuel in those as we do in our automobiles. The underhood heat those generate is extreme because there is little airflow under the hood and the engine is laboring mightily during the mowing process. Why does this "vapor lock phenomenon" not seem to affect these machines?
 
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