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So the Packard starts stumbling then the electric pump goes on for a short time and it stops stumbling, then the pump goes off and it runs fine?? These are not marks of vapor lock unless the car/fuel has cooled down in that short interval and NEVER heats up again.

Vapor lock occurs before the fuel pump, bubbling in a see through filter is common up here summer or winter... and the cars run fine.

Some people will do what they've always done, some will learn something new.

From your recent post " A test or series of tests run on one car in NJ does little to make it a fact extant." Facts either exist or they don't, what facts I report from NJ are by definition extant. I guess "facts" from Texas are better facts??, I guess your uncontrolled "facts" from one care are not LOL.


A controlled experiment would get closer to the real cause.

Note: I made an error and thought it was the Dart that had the electric pump

the dart doesn't have an electric fuel pump and the filter is after the fuel pump, not before it.

run summer gas and I get no bubbling, run winter mix and I get bubbling, run winter mix 15 gal to 5 gal race gas and no bubbling. not sure how much more factual you can get then that. and yes I ran the car completely out of gas at each change over.


the Packard is the one that I use the electric on and it solves my problem well enough that I can move on with life and drive it.

also, I didn't post the quoted post....

Good afternoon all...I will vouch for the 75 miles an hour in Phoenix and for the extreme temperatures under the hood for old cars here.

Between driving the 1949 Packard and the 1931 Model A Ford...I have seen bubbles in the glass fuel bowl in both machines. Running some Marvel Mystery Oil in the fuel does retard the bubbling/boiling as does a bit of diesel...both approaches are used here in the desert in the summer time.

At the Saturday car shows, one can see that a good number of classic cars do have electric fuel pumps to help out. I do not, as my rule is that if it is too hot for our old machines than it is too hot for me! Big Kev must have had the same experience in Riverside, California!

Fred...It seems to me that in New Jersey, you can't put on enough clothes for your coldest days...here in the Sonoran Desert...we can't take off enough clothes without being arrested...and some days, all your bare hide would do is to become burnt to a crisp. Jeans, a long sleeve white T-Shirt, good western boots, and a good hat are the ticket. Ernie

Bubbles in glass fuel bowls occurs here in NJ summer and winter and the cars run fine. Now that I have the 48 Custom 8 starting and running fine I will make it Phoenix weather in our paint booth and see.

"Vapor lock BEFORE the fuel pump".

Thaat is a common misconception based on sound conjecture of lowered pressure (suction side of pump) nd is grossly insignificant.

SEE THE PACKRD PUBLISHED DOCUMENTATIO LINKS AT THE BOTTOM OF THIS POST!!! The link has been there at 3 or 4 years of EVERY post i have made It is titled:
Vapor lock demystified.

Vapor lock occurs INSIDE the pump OR between the pump and the carb (pressure side of pump).

"Vapor lock BEFORE the fuel pump".

Thaat is a common misconception based on sound conjecture of lowered pressure (suction side of pump) nd is grossly insignificant.

SEE THE PACKRD PUBLISHED DOCUMENTATIO LINKS AT THE BOTTOM OF THIS POST!!! The link has been there at 3 or 4 years of EVERY post i have made It is titled:
Vapor lock demystified.

Vapor lock occurs INSIDE the pump OR between the pump and the carb (pressure side of pump). or possibly inside of carb.

After setting for 2 weeks or more:

Fill a lighter fluid can with gas. LOOSEN (do NOT remove) wing nut on aircleaner. Squirt gas around wing nut stud. It will flow down into carb.
On engines much over 300 CID it will require AT LEAST 2 table spoons full of gas squirted down carb. Just guess at it.

Keith, there is nothing in there that says vapor lock does not occur on the suction side.

It's a fact that liquids boil at lower temps when subjected to lower pressures.

Once that fuel starts to boil in the line, it reduces the ability of a front mounted fuel pump to suck the fuel from the tank. Primary the section of line right before the pump that is subject to engine heat.

Hence when you pressurize the line with a tank mounted pump, all of a sudden those problems go away.

I will agree until driven a car in the Southwest, where the outside temp can be over 110, you just don't understand how hot things can get. You're dealing with higher that normal underhood temps, radiant reflection from the asphalt etc. Also, let us not forget how the underhood temp can swing upwards once the car is shut off. I think that is the point at which fuel in the pump, in the line between the pump and carb and the carb itself can be subject to higher than normal heat.

A summer day in NJ for sure is not the same as a summer day in PHX.

Sure, Boyles law.

But here's the problem:
Whether PHX or the Actic circle, the Suction side of the fuel line is rather LOW in the car. The pressure side of the line (pump to carb) rises high AND USUALLY CLOSE TO ENGINE. Guess what??? Heat RISES.
There are other factors that keep the feed line (from tank to pump) much cooler than the pressure line from pump to carb.


Also note that MOST (which means that not all) fuel pumps are usualy mounted LOW on the engine and up near the fan.

I suppose one would have to run somekind oof a controlled test taking temps and pressures (and neg. pressures) to ever, once and for all, provewhere the boiling is taking place.

Just because the pressure line (pump to carb) is pressurized does NOT mean that the fuel can not still get hot enuf to boil.

Like wise, just because the tank to pump line is under neg. pressure does not necessarily mean that the fuell WILL boil.

It all has to do with threshold points of each part of the system.

Most likely, the old cloths pin trick, albeeit a feeble attempt, but nonetheless an attempt to wick heat away from the PRESSURE line.

The electric fuel pump craze is mostly akin to the diskbrake and e-ignitionn conversion fads. Electric pump is simply a quick fix for OTHER problems that need to be addressed.

However, i can imagine that high heat areas cerrtainly will cause the vaporlock most frequently.
But it does NOT occur in the feed line. It occurs in line from pump to carb.

Furthermore:
PHX or Alaska, cars were certainly driven those places too back in the 30's , 40's nd 50's...... And i seriously doubt that PHX was any cooler baack in the 40's or 50's than it is today 2017.