Vapor lock?

R

rlhinit

Member
This might sound strange - when your flat head gets "Vapor lock " is it in the carb or the fuel pump ? I remember years ago (?) when you got vapor lock you'd pour water over the fuel pump. Then wait for it to cool down - hopefully it would start. The reason I'm asking this is because earlier this season I experienced vapor lock - out where there was no water available - sit and wait I did. I have an electric in line flow thru pump - which feeds the manual .( I use this for starting after car hasn't been used for awhile)

I'd like to keep the manual pump and use the electric only when needed. I recently by-passed the manual and use the electric only. Can't stand the noise.

What do you guys think of this ? Am I doing the right thing ?

Rayzor
 
Vapor lock can happen to any fuel system line or component that is subject to enough heat to get the fuel to boil. It's most common during the first few weeks of warm up after winter starts to turn to spring. Winter fuels in some higher altitude areas have high enough volatility that they will easily boil when weather warms even to normal temperatures. When the less volatile fuel reaches the pumps, the problem will generally go away. In extremely hot climates, insulation of areas that have extreme temperatures can solve a vapor lock problem such as shielding or insulating fuel system lines or adding insulator blocks or heat shields to the carburetor base.

Many times vapor lock can be a mis-diagnosis since some electrical components can degrade with higher heat and cause ignition instability which give similar symptoms.
 
rotorwrench, I have since then - actually yesterday - installed a cotton phenalic spacer. Haven't been able to test drive it as of yet.

Thanks for the info. Rayzor
 
Get a cheap infrared temp tester and see what's going on. I have never had vapor lock, even in Florida. I know it is supposed to exists, but I have never had it.

Gas goes into heated vapor at 213 degrees. Regular gas, not ethanol fuel. No idea there.

Not gospel, just my understanding.
 
Some here say ethenol gas is more prone to vapor lock.

My '47 coupe came to me with a noisy 6-blade (truck?) belt-driven fan. So I changed to a quiet electric fan. Thereafter I began experiencing vapor lock.

A prior owner had insulated the gas line from the tank to the pump with aluminum foil covered foam tubing, but the gas line from the pump to the carb remains exposed. He also installed an Airtex elec pump which I use for starting. It doesn't seem to help with vapor lock. I just opened the hood and waited about five minutes and the engine would start fine.

So apparently the electric fan wasn't moving enough air thru the engine compartment. I reinstalled the 6-blade fan. So far so good.
 
The only vapor lock problems I have encountered was when I worked up the the western mountain states of Colorado, Utah, and Wyoming. We would have a heck of a time moving our refueling trucks around during the early part of the spring thaw. The high volatility fuel would boil very easily at the higher elevations. The change over to summer lower volatility fuel was sometimes slow due to the logistics of the region. There were times when we wished we had diesel truck engines at that time of year but they would have been worse in the cold weather for starting so we stuck it out.
 
I have never ever had vapor lock since these were new. But for a short period I had a
1947 Cadillac what was it? 346 flathead. Yep cold water cause those, the exhaust was
on top side the carb and fuel pump.......
 
I experienced vapor locking on my 41 pick up with the flat head V8. I resolved my vapor locking issue by supplying a electric in line fuel pump to the original fuel pump and all my issues went away.
Vic
 
I have suffered both vapor lock and its symptom twin, hot coil breakdown. Coil situation fixed with Pertronix conversion and their 40,000 volt coil. I get a good blue spark that will jump half an inch, even when the engine compartment is at its hottest.

I have clear fuel lines between mechanical pump, pressure regulator and carbs, and can watch the bubbles come out of the fuel pump. The electric pump mounted near the tank takes care of that. It is on a switch to use only for starting after sitting for days, or vapor lock situations.

The carbs are on risers and have phenolic spacers, so they do not get too hot. The fuel pump is the culprit because it has no insulation from engine heat and does not get much cooling air flow.
 
I suffered vapor lock just a few days ago. Poured some gas down the carb and it fired back up.
 
Invariably vapour lock can be caused by the proximity of the petrol pipe to the exhaust manifold. A common problem with 4 cylinder cars and in particular the old Ford E93A
 
During hot weather whenever I shut the engine off I open the hood on my pickup and it helps by letting the heat escape from the engine compartment. If I don't open the hood and the engine is shut off for more than a few minutes it is hard to start and I have to open the hood and wait for it to cool off anyway.
 
Kerk said:
I would send the coik to skip for rebuild, It Worked for me! kx
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????? I thought the problem was the carb not getting filled with fuel ? And the engine runs when the carb is filled.

How would a coil rebuild help the problem ?

Sal
 
The reason an original coil fails when hot is that the internal resistance goes up, reducing the spark available to the distributor. The originals used a kind of wax paper as an insulator, and time and vibration can cause the material to disintegrate. Send your coil to Skip Haney if it is an original, even if it runs OK. It is good insurance for trouble free fun with your car.
 
scicala said:
????? I thought the problem was the carb not getting filled with fuel ? And the engine runs when the carb is filled.

How would a coil rebuild help the problem ?

Sal
Click to expand...

Sal-

I believe this was the poster's way of saying, "It's possible your problem isn't vapor lock at all, but rather your coil getting too hot." Drolston alluded to the same thing. Still, the dots were not really connected.
 
jagnweiner said:
Sal-

I believe this was the poster's way of saying, "It's possible your problem isn't vapor lock at all, but rather your coil getting too hot." Drolston alluded to the same thing. Still, the dots were not really connected.
Click to expand...


It is certainly something to consider. May not be the issue.
 
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