Witch hunts, the Loch Ness Monster, and Vapor Lock, Challenging Your Beliefs

[darren]

I also have experienced  the   "vapor lock"  problem.... As Mr. B stated our gas will ignite faster... I feel Evan if you do every thing you can  ie heat shields  wrapping the lines  electric fuel pumps.. have a extra line to the tank for continue flow..  Some might say "fixed there problem".... BUT I say IT needs a upgrade... The carburetor jets are not for our gas nor the brass float  the material "they used " is not what the engineers would use today... Material and upgraded spark control etc.  etc.   NOW there are some that say I never have a problem or some that say I do have a problem... Just remember we are not driving our cars like the "other guy"    Engineers have alway "readjusted " the thought pattern.. Today the engineers consults the gas company's first then make a compatible arrangement..  Now there are and will be some that say "my car works perfect as is!"  And I say thats the case with anything ... If one bought say a camera and was talking about it .. you know someone in the room would say thats junk and some one would say  I love  my camera... SO I say the loch Ness Monster lives or not within  our own situation... Happy PLY-mouthing ...DANiel

[Go Fleiter]

For whatever reason my car didn?t start for nearly a minute after having parked hot. Plym46?s description fits my experience: when the pump pushed Bubbles (?) out and fresh gas arrived, it run. provided, I hadn?t drowned the spark plugs inj the meantime! So I put the shieds too and installed an electric shunt gas pump. So I don?t use the pitiful starter motor any more to turn the engine only for delivering fresh gas.

[elmo]

I don't want to stir things up to much , but i can assure the disbelievers , vapor lock does exist . but i do not believe in witches the lock ness monster , and not to sure about green martians .over the last 40 odd years i have owned 4 chrysler product cars , a 1938 Dodge, 1937 plymouth bodied chrysler , 1954 Desoto diplomat which is a Plymouth in disguise and a 1939 S6 DeSoto . all of them  have at some time suffered from vapor lock , i used to carry a jar of water which i poured over the fuel line to try and cure it  with some success, it was not untill i fitted a heat shield over the fuel pump , an asbestos type original shield , (which i picked up at a swap meet ) between the carb and the manifold , and wound the fuel line from the pump to the carb with asbestos string that i fully cured the problem . since doing all this i have never had a vapor lock problem. I know using asbestos is frowned  on but it cured my problems and unless it is breaking down and turning to dust there is no problem , but if you dont want to use it make sure that your  fuel line from the pump to the carb has not been replaced with copper pipe (copper attracts heat ) and reroute your line as far from the manifold as possible.

[plym_46]

Quote from Wikipedia "This article does not cite any references or sources."

It is does support my contention that if "vapor lock" exists it exists in the fuel pump, and as noted in vehicles with a low pressure (read FORD) fule pump located higher than the fuel tank (read Ford) and is not consistant with the fact the MOPAR engineers located the fuel pump nearly at the same level as the tank.  If you break the line between the tank and the pump, fuel will leak from the lind due to gravity.  The job of the pump in the MOPAR design is to deliver it up to the carb not suck it up from the tank. 

Any air leaks in the line from the tank to the pump will lead to a condition described in the Wiki article, however vapor delivered to the carb pushed by a non compressiable liquid, will vent to the atmosphere, it will not and can not prevent liquid fuel being delivered if the pump is supplied properly and in good mechaical condition.

[Lew]

supposedly having the heat shield over the fuel pump is supposed to reduce vapor lock incidence.
LR

[POC-Admin]

I don't want to cause any fights but Wikipedia has an entry on Vapor Lock

http://en.wikipedia.org/wiki/Vapour_lock

In the last paragraph it mentions "Historically, gasoline was a more volatile distillate than it is now and was more prone to vapor lock. Conversely, diesel fuel is far less volatile than gasoline and thus these engines hardly ever suffer from vapor lock. However, diesel engine fuel systems are far more susceptible to air locks in their fuel lines as standard diesel fuel injection pumps rely on the fuel being non-compressible. Air locks are caused by air leaking into the fuel delivery line or entering from the tank rather than the fuel evaporating in the system."

I guess this fits with the old bubble in the bloodstream will kill you - I have been told by experts that it would take quite a few bubbles to kill you but I don't think I want to try that one.

Vapor lock - real or not?  That is the question?

[Cliff54]

right on ED!  ;D

Cliff54

[Ed_Ungerman]

Nothing but wood for vintage Plymouths.  ;D

[plym_46]

I read somewhere that the pink plastic ones have the best R value, But their flat spring negates the value of the coil wound sprigs of the vintage wooden units.

Also technically clothes pins are the wooden one piece push on devices, the spring equiped two piece affairs are clothes clips whether they are wood, plastic or the new light wight carbon fiber and titanium ones.

[Cliff54]

.....but my Plymouth looks cool with wood clothes pins on the gas line!!   ;D


Cliff54

[plym_46]

Not so sure about Santa but Salem is way over hyped......

[JimCno]

So what are you trying to tell me? Are you saying that there is no Santa Clause?

I'll tell you right now, he's real! I saw him at the mall last year.

If (sniff).... he's not real (sniff)... then (sob, sob) just what is?

Bwa-ha-ha-ha!

[Don Coatney]

Greg;
Your posting reflects my thoughts. Thanks for taking the time to write it all out. As you mentioned the entry of air on the suction side of the fuel pump will cause a problem but not on the discharge side. It is very unlikely that there are temperatures high enough to vaporize gasoline in the fuel line running from the tank to the fuel pump on Mopar's running flathead engines.

[plym_46]

Is one of these thing not like the other.  Do you believe in Santa Clause, the easter bunny and forgiving the National Defficit???

Assumption:  A bubble of air or fuel vapor can bock the flow of fuel under pressure.



Fact!  Fluid under pressure will always move air bubbles or vapor when vented to the atmosphere.  Example bleeding brakes, attaching a new garden hose to your out door tap.  If not fact brakes could not be bleed, and you could never get water out of a new hose.

Fact!  Your carburator is vented to the atmosphere.

Fact!  Your fuel pump produces 3 to 5 lbs per square inch of fuel pressure.

Fact!  This pressure cannot be resisted by a bubble of air or gas vapor in the line from the pump to the carb. (laws of hydrodynamics and physics here folks)

Fact!  The bubble will want to rise and can do so through a fluid ( pour youself a carbonated beverage as you ponder this) to the highest point within a colume of fluid.  It would be stopped here by the needle and seat but would be the first to exit when the needle opens.

Fact! The air or vapor pushed by the fuel pressure will escape to the atmosphere once it is pushed past the needle and seat.  Yes folks that tube that comes out of the carb is a float bowl vent, as the carburetor could not work if the chamber was presurized. (it would be like fuel injection albiet a bit uncontrolled)

Proof!  Accepting the above facts rules out vapor lock (It will not however rule out your belief system if you won't let it, and still need to excuse hot start problems)  See fuel perculation post under hard starting 54.

Why does putting ice on the line help ( probably the time involved in getting and applying the ice is the key to clearing the puddle fuel in the intake) ?
Why does throwing a witch in the water prove she is guilty or innocent?

Exception!  If the fuel in the lower chamber of the fuel pump vaporizes ( which seems highly unlikey) Your pump will them be trying to pump a fluid through a bubble which is difficult.  However since the bottom of the fuel pump is lower than or at least level with the bottom of the fuel tank, (yes it is look at the frame drawings in the manual) it seems as gravity would soon cure this problem. You might also want to check the rubber line between the frame and pump to assure it is not collapsing what hot as this will block fuel flow to the pump, also any air leaks on the suction side of the pump  will cause flow problems.

So if ya wanna pick a fight, you're gonna be fighting Newton, Bernulli, Pascal, Torricelli,  and a couple of other guys.

Start here with your efforts;

pressure applied to a confined fluid at any point is transmitted undiminished throughout the fluid in all directions and acts upon every part of the confining vessel at right angles to its interior surfaces and equally upon equal areas.


Now if your are talking about Ford's design of having the pump on top of the engine, higher then the tank, then you might have something.