Vapor lock 1 and 2

The most typical problem with vapor lock is vaporization of the fuel in the fuel pump, not total boiling out of the fuel in the carburetor bowl. Anyone that's ever had vapor lock knows that if you wait long enough the fuel pump will cool down enough to condense the fuel back into liquid so that the pump will pump. (That can even be rushed by pouring water on the pump, pushing a half grapefruit onto the top of the pump, etc). So, overheating the engine then leaving it all night is, of course, going to allow the pump to cool and condense the fuel and have no problems starting in the morning. The true test would be taking a 30 mile drive in 90+ temperatures, stopping and parking in the sun without opening the hood for 20 minutes, then starting up and seeing what happens. I look forward to the results of that test. Let us know how it goes.
 
Old Henry said:
The most typical problem with vapor lock is vaporization of the fuel in the fuel pump, not total boiling out of the fuel in the carburetor bowl. Anyone that's ever had vapor lock knows that if you wait long enough the fuel pump will cool down enough to condense the fuel back into liquid so that the pump will pump. (That can even be rushed by pouring water on the pump, pushing a half grapefruit onto the top of the pump, etc). So, overheating the engine then leaving it all night is, of course, going to allow the pump to cool and condense the fuel and have no problems starting in the morning. The true test would be taking a 30 mile drive in 90+ temperatures, stopping and parking in the sun without opening the hood for 20 minutes, then starting up and seeing what happens. I look forward to the results of that test. Let us know how it goes.
Click to expand...

READ my post it's titled V1-1 and VL-2. Vl-1 was the fuel boiling in the carb after shut down. I posted this was no longer a problem with Shewman's 1/2" ventilated carb space, VL-1 over and done.
VL-2 was fuel vaporizing in the fuel pump when the fuel pump gets between 130 and 135 at the top above the diaphragm where the fuel is.
Driving the car, getting it hot and letting it sit in no difference than getting it even hotter in the garage and letting it set for a period of time and restarting. I will be driving it later this week and will report back but the results will be the same as last nights findings. Static tests on some problems are sometimes better than driving, the conditions are controlled and the same each time. G.M.
 
who sales the shewman"s ventilated spacer. does anyone have a contact. i installed the airtex fuel pump and would like to have the spacer to.
 
I installed the spacer but it didn't do me any good because the heat that affects the carburetor after shut down is coming from the hot air under the hood in the engine compartment as much as from the hot engine block.
 
G.M. said:
READ my post it's titled V1-1 and VL-2. Vl-1 was the fuel boiling in the carb after shut down. I posted this was no longer a problem with Shewman's 1/2" ventilated carb space, VL-1 over and done.
VL-2 was fuel vaporizing in the fuel pump when the fuel pump gets between 130 and 135 at the top above the diaphragm where the fuel is.
Driving the car, getting it hot and letting it sit in no difference than getting it even hotter in the garage and letting it set for a period of time and restarting. I will be driving it later this week and will report back but the results will be the same as last nights findings. Static tests on some problems are sometimes better than driving, the conditions are controlled and the same each time. G.M.
Click to expand...

Be sure that your driving test is under the same circumstances as previous ones in which you have had vapor lock affect the fuel pump that either made it hard to start or die shortly after starting then not starting again. Any difference in circumstances between the new test drive and previous drives with vapor lock will not be a "controlled" test that proves anything.:)
 
FlatheadTed said:
its commonly thought that the fuel jumps the 1/2 " up to the needle valve and siphons back to the pump .
Click to expand...

Fuel can't syphon through the air it the top of the carb fuel bowl. It would have to be pressurized at the bottom to raise the fuel then the needle valve would close??? G.M.
 
Old Henry said:
I installed the spacer but it didn't do me any good because the heat that affects the carburetor after shut down is coming from the hot air under the hood in the engine compartment as much as from the hot engine block.
Click to expand...

I don't believe it. Everyone else who used Bob Shewman's 1/2" vented spacer got results. But of course your one of the few that his thermostats didn't work either. You had a crusade against any product Bob made on this fourum before you ever had them?? What seems to be your game?? G.M.
 
Old Henry said:
Be sure that your driving test is under the same circumstances as previous ones in which you have had vapor lock affect the fuel pump that either made it hard to start or die shortly after starting then not starting again. Any difference in circumstances between the new test drive and previous drives with vapor lock will not be a "controlled" test that proves anything.:)
Click to expand...

It can't get vapor lock in the pump until the fuel reaches 130 degrees and I can't get the fuel anywhere near that with the fuel return line. No 130, no vapor lock. What's the sense of looking for something that isn't going to happen. As far as testing I probly have another 25,000 on this 39 testing water pumps, thermostats, alternators and other products in the shop. I don't think I need to be told how tor run a test. G.M.
 
jerry shook said:
who sales the shewman"s ventilated spacer. does anyone have a contact. i installed the airtex fuel pump and would like to have the spacer to.
Click to expand...

Jerry Bob's phone number is 1-610-933-6637. He is in Pa. His email is
gadgiteer@aol.comr Your talking about an Airtex fuel pump which is just like the original Ford pump. This has nothing to do with preventing vapor lock. I put a return fuel line in the pump to carb line using an Airtex fuel check valve on the return line. This allows a portion of cold fuel from the tank to keep circulating through the fuel pump cooling it as it returns through the return line back to the tank. G.M.
 
Going by some earlier posts on this thread you can see that some people beleave just that ! .That that the carb bowl can empty out by draining back .Has any one bothered to lift the carb top to see the fuel level in a vapour lock situation ?
1952henry said:
Right you are.
Click to expand...
 
Ted since you brought it up that would be a good project for you. Please report the results. G.M.
 
FlatheadTed said:
Going by some earlier posts on this thread you can see that some people beleave just that ! .That that the carb bowl can empty out by draining back .Has any one bothered to lift the carb top to see the fuel level in a vapour lock situation ?
Click to expand...

The engine doesn't die immediately when the fuel pump vapor locks and stops pumping. It will continue to run until the gas is all gone from the carburetor and the fuel pump isn't replacing it. That's when the engine dies and won't start again until some gas is pumped into the carb either by cooling the mechanical pump to get the gas vapor to condense back into liquid so that it will pump again or by pumping gas into the carb with an auxiliary electric pump. So, when the engine dies, obviously there is no gas in the carburetor bowl. If there was, the engine wouldn't die. Don't need to take the top off of the carburetor nor have a sight glass on the carburetor to know that. It's common sense.:cool:
 
GM I might take you up on that .
G.M. said:
Ted since you brought it up that would be a good project for you. Please report the results. G.M.
Click to expand...

Prof Henry no offence meant.!
What I cannot understand is how can a electric pump works but a mechanical one doesn't ,since they both have a diaphragm.
Keep up the good work with your road trips .
 
Last edited:
Flathead Ted:
It's the locatation of the pump's
The Mechanical pump is on the motor, ( Picking up the heat of the motor )while the electric is near the fuel tank, (a much cooler area )
I don't know if any one has tried to heat up the electrical pump but More then likely
It would not pump.
 
BILL WZOREK said:
Flathead Ted:
It's the locatation of the pump's
The Mechanical pump is on the motor, ( Picking up the heat of the motor )while the electric is near the fuel tank, (a much cooler area )
I don't know if any one has tried to heat up the electrical pump but More then likely
It would not pump.
Click to expand...

And, it's not only the difference in temperatures but also the electric pump is located below the level of fuel in the tank so it is gravity fed whereas the mechanical pump is above that level so that, if it can't suck the fuel above its level in the tank, it can't get any. And it's not just the temperature of the mechanical pump that makes stop pumping, it's the vaporization of the fuel in it so that the pump can't pump it. So, to merely heat up the electric pump wouldn't keep it from pumping until the fuel in it vaporized. That would require all the fuel in the tank to vaporize or be gone since the liquid fuel is being gravity fed to the electric pump.
 
Last edited:
that is probably one of the reasons alot of manufactures started placing the pumps inside the fuel tanks. to get them away from the heat of the motor and to have the gas keep them cooled.

another thought: with the c***y motor, the pump is mounted low on the right front of the motor and that provides a place in directly in the flow of cooler air and puts the pump at the same aproxamate level as the gas tank so it does not have the inhearent problems of the ford's placement that has to pull fuel up to the top of a hot motor where the fuel pump sits captive in non flowing hot air.

i do have a GM motor in my 50 and run a stock GM fuel pump on the right front in the air flow, the fuel line has been re-routed down to frame level. the motor has a 195 thermostat and AC and so runs at the 200+ degree range i have never have any problem with vapor lock.


i believe that if a person is one is going to use a stock ford fuel pump on top of a hot motor, at some point they probably will experience vapor lock. rather than going through all this "experimentation" of fuel return lines, check valves and everything else being expereminted here in this thread, doing what Old Henry has done, installing an in line, pull thru axuxilary pump down low on the frame, in the cool air flow and at the same level as the fuel tank, with a "when needed" switch (what i did on my other 50s and 41 PU) is a simple and effective souloution to this issue.

it just seems to me that what has been said here on this thread, the cure seems to be "over engineering" at it best. there is a simple souloution avalable without going overboard..

just my thought... don
 
You must log in or register to reply here.
Back
Top