Vapor Lock

Aeroman99

Aeroman99

Member
I'm sure there is a tread out there on this subject but I'm going to bring it up again. Last summer was the first time I had my 46 S/D out sense I finished the restore on it. It has the 239 flathead in it nothing fancy all original equipment on it. 2 or 3 times I had it out on hot days 90+ it vapor locked on me. The engine was running about 210-20 some where in that area and she would just stall out on me. Id Let it set for a while and it would start back up and run a while 10-20 miles down the road then do it again. Last week I installed a electric fuel pump on it in hopes that this will solve my V/L problem. I also have the mechanical pump still hooked up. Should I take the mech pump out of the system all together or will it be ok to leave it in? I also installed thermostats in the engine hoping that might help keep the engine cooler. Any thoughts on the subject.
Thanks.
 
Aeroman99 said:
I'm sure there is a tread out there on this subject but I'm going to bring it up again. Last summer was the first time I had my 46 S/D out sense I finished the restore on it. It has the 239 flathead in it nothing fancy all original equipment on it. 2 or 3 times I had it out on hot days 90+ it vapor locked on me. The engine was running about 210-20 some where in that area and she would just stall out on me. Id Let it set for a while and it would start back up and run a while 10-20 miles down the road then do it again. Last week I installed a electric fuel pump on it in hopes that this will solve my V/L problem. I also have the mechanical pump still hooked up. Should I take the mech pump out of the system all together or will it be ok to leave it in? I also installed thermostats in the engine hoping that might help keep the engine cooler. Any thoughts on the subject.
Thanks.
Click to expand...
In my opinion your running too high a temp in the motor,fix that and your problem might go away. Could also be a weak coil doing it also.They tend to act almost the same. ken ct.
 
maby the coil, i have driven my 36 pickup on some hot days with no trouble. i have had skip rebuild my coil
 
I have never had vapor lock stall my engine while I am driving. My belief is that while driving the cool gasoline being pumped up from the tank prevents it. My vapor lock has always happened after shutting the engine off on a hot day then trying to start it up again within 30 minutes. During that time the fuel in the pump sitting on top of the hot engine vaporizes and won't pump any more until it's cooled down. I've been able to speed up the cooling process by pouring water on the fuel pump to get going again. An electric fuel pump can also "prime" the mechanical pump to accomplish the same thing.

Your stalling while driving problem sounds like something other than vapor lock. It sounds more like an ignition problem. Next time it stalls while driving, first check for gasoline in the carburetor by removing the air filter and looking down into the carburetor while "pumping" the accelerator to see if gas is squirting into the carburetor throat, if so, it's not vapor lock or any fuel problem. If you have fuel then you check and see if you have spark. That's easiest done roadside by simply pulling off a spark plug wire and holding it close to the block while cranking the engine to see if you have spark. If not, then it's an ignition problem, not vapor lock, and you have to find out what. A weak coil that overheats and quits while driving then starts up again when cool could be it as previously suggested.

You can leave the mechanical pump in line with the electric pump.

Installing thermostats won't make your engine run cooler, they just stabilize the temperature so it doesn't fluctuate so much.
 
Quite often the older coils will fail when they get hot. Cool down and away you go again. Try a different coil. Make the checks as Old Henry has posted.
 
Excellent advice all, and I get a kick out of flatjack's advice to try a different coil! Back in the day, we all used to carry a cardbooard box full of old coils for this very reason. We'd get stuck and go eeny meeny miny moe, pick a coil, and away we'd go. Funny thing about it, all the coils were in the same shape, and we could have simply removed the faulty (overheated) coil, and replaced the same coil, as all it needed was a cooling off period! Get your coil rebuilt by an expert. DO NOT buy a NOS or new coil. There are more than one rebuilder, but the guy most are familiar with is Skip Haney in Florida.
www.fordcollector.com

As Ken says, your temp is too high, which is a contributing factor to the problem. Skip Haney also rebuilds water pumps with high volume output. Before going that route, though, confirm that your radiator is not clogged, and your block. A "Restoration" doesn't always mean these things are taken care of. Use a 3# radiator cap also. This will raise the boiling point of the coolant, which should be plain water with an enhancer such as "Water Wetter". Use no antifreeze if you live in a moderate zone. Same thing about thermostats, Old Henry couldn't have said it better.
 
I did have a problem with the distributor this fall. The little spring loaded pin in it stuck and wasn't making a connection. That was easily fix once I figured out the problem. When that happened it just died. But when I say it stalls I should have been a little more clear. It will start to spit and sputter and them it will stall. There was a couple of times also it ran fine until I shut it off then it wouldn't start I have to call dear old Dad to come town me home and on the way I put it in 2nd gear dumped the clutch and it fired right up. I did check the carb and there was no gas flow. which led me to believe it was V/L. My car is still 6v. Can any coil be used or dose it have to be a 6v coil ? Also would it hurt anything to run an 8volt battery in it ?
Thanks again.
 
The coil in my car isn't serviceable. Its just a regular old coil. Now the question is is there a difference 6v 12v ? or will any old coil work ?
Thanks again.
 
No, don't use an 8v battery. That's just treating the symptoms rather than addressing the cause. Your coil is "serviceable". Send it to Skip. Do not buy a new coil unless it's a modern barrel type, which will work fine, but will of course not look correct. If you do that, check to see if it has an internal resistor, in which case you must bypass the stock resister. I'm not that familiar with the '46 Ford, and am thinking the resister is still under the dashboard, but may be at the coil mount?
 
ford38v8 said:
Back in the day, we all used to carry a cardbooard box full of old coils for this very reason. We'd get stuck and go eeny meeny miny moe, pick a coil, and away we'd go.
Click to expand...

I still carry an extra coil along with a lot of other "extra" stuff. Just in case.
 
Aeroman99 said:
when I say it stalls I should have been a little more clear. It will start to spit and sputter and them it will stall.
Click to expand...

That sounds a little bit like a plugged fuel filter if you have one (they weren't stock.) If you have a filter replace it and it might fix you up. (I carry a supply of those with me as well.)
 
Aeroman99 said:
The coil in my car isn't serviceable. Its just a regular old coil. Now the question is is there a difference 6v 12v ? or will any old coil work ?
Thanks again.
Click to expand...

6 volt and 12 volt coils are different and must be matched to the voltage of the vehicle.

Personally, I have had very good service from the new original style coil I bought from C&G many years ago still available here: https://secure435.hostgator.com/~dlvry40/ufolder/ShowProducts.php?c=1&s=19&g=147&t=1050&tn=
 
Here are stock resistors for the stock coil. My original stock one is the ceramic one.

https://secure435.hostgator.com/~dlvry40/ufolder/ShowProducts.php?c=1&s=19&g=148&t=1058&tn=

It may be installed as per photo. Left wire is connected to distributor side of coil then to the distributor. The right wire comes from the ignition switch to one side of the resistor then through the resistor that is connected to the battery side of the distributor on the right in the photo.

Your resistor may be under the dashboard with the headlight circuit breakers on panel shown and available here: https://secure435.hostgator.com/~dlvry40/ufolder/ShowProducts.php?c=1&s=19&g=148&t=1057&tn=
 

Attachments

  • Coil Resistor.jpg
    Coil Resistor.jpg
    292.9 KB · Views: 26
Last edited:
From what I see here and am being told my car doesn't have the original coil. My coil is a modern style coil. Maybe I should look around and find the correct coil for it.
Thank you all for all of the information. What can I do to cool my motor down during the hot summer months. In the spring months it ran 160. In July it ran 200 210 and it was well into the 90s. I didn't drive it again until the end of October due to knee surgery. Id like to get all of the bugs worked out of it during the winter season.
 
Aeroman99 said:
What can I do to cool my motor down during the hot summer months.
Click to expand...

To aid in cooling better (from most important, easy, and cheap to less important, expensive, and hard):

1. Make sure your radiator is clean without any deposits. That is the most critical component in transfering the heat of the engine to the air. You can see the ends of the tubing by looking into the radiator through the radiator cap. If you see any deposits at all it needs to be cleaned. Sometimes that can be done without removing the radiator by running Prestone Radiator Cleaner (not the flush) in it for 4-6 hours while driving around then flushing it out. That sometime removes the deposits. If not, it must be removed and "rodded out."

2. Make sure there is plenty of water in the cooling system. It should be about 1 inch below the radiator cap to allow for expansion of the coolant, no lower.

3. Use either a "water wetter" or just regular anti-freeze to aid in the heat transfer. Distilled water is even better than regular tap water.

4. If you are using thermostats (which I believe you should year 'round to stabilize the engine temperature and aid quick warm up to optimal operating temperature, even in the summer) make sure they are both working right by testing them in a pan of water warming on the stove with a thermometer in it to see that the thermostats open when they should.

5. Some put higher volume water pumps in altough I'm not sure they make enough difference to be worth the money.

6. Some put electric fans in front of the radiator to increase air flow through it at slow speeds such as in parades. Personally, I've crawled along in many a parade on a hot day and have never had a problem with heat.

7. Finally, the ultimate is to remove the engine and "boil it out" to remove any deposits in the block that may be interfering with heat transfer.

In all of the years of making the flat head engines I believe Henry thought of everything and designed and built the engines for optimal performance as they were stock without a lot of fancy "tweeking" of the cooling system as many do. The "tweekings" don't hurt anything but I don't think are worth the money.
 
Last edited:
Every time a thread starts any where on this topic, there will be those who say that vapor lock doesn't exist. Had this same experience when I posted on an old Econoline website. I think the people who don't believe in it, haven't experienced it first hand.

When ethanol replaced MTBE as an oxygenate in gasoline here in NJ, I had a problem immediately with my 63 Econoline. I probably wouldn't have believed it if I hadn't experienced it. I was stopped at a traffic light on a hot day and my engine started to sound like it was running out of gas. Tried to give it a little gas and it coughed and quit. Even though my temp gauge didn't indicate a problem, I thought that heat might still be the culprit since the Econoline's engine is in an enclosed box. Opened the engine cover and waited for things to cool down. Still wouldn't start. Ended up having it flat-bedded home.

Looked down the carb as I stroked the carb linkage and noticed there was no gas, Checked the fuel bowl and it was dry. Long story short... Took the fuel line off and burped it to get the bubbles out and it started right up and ran just fine. It happened a couple more times before I had the time to work on the problem.

Econolines of that vintage have insulation on the fuel line at the engine. Mine didn't have it. Put that back on. Went with a six blade fan and machined a phenolic spacer for the carb. Somewhere between the three changes, I solved the problem. Never happened before the addition of ethanol. Might have been borderline before. But the change in fuel was the tipping point in my case.

Gasoline is blended differently depending on the season. A friend of mine who works for Exxon here was telling me that cold weather gas can be a problem on an unseasonably hot day as well.
 
This past summer my car would not start after running to full temp. It would need to cool down a bit before it would start. It was the coil!
 
ct1932ford said:
This past summer my car would not start after running to full temp. It would need to cool down a bit before it would start. It was the coil!
Click to expand...

Hey I'm not saying that there aren't other reasons why an engine might quit on a hot day... I've had bad coils as well.

Chevron publishes an extensive study regarding modern fuels. Look up 69083_MotorGas_Tech Review.pdf on the internet to download a copy. It's important to consider that gasoline is formulated to perform best in engines that are most commonly used. Today that means a closed and highly pressurized fuel system. Running more volatile blends in our older cars can on occasion cause unintended problems. Even mixing summer blend into a tank that contained winter blended fuel can be an issue.

In my case, it was easy to determine whether I had a fuel or spark issue.
 
You must log in or register to reply here.
Back
Top