🚀 go-pugleaf

> Im sorry Randle but there is no such thing as "Vapor Lock" in today's
> automobiles.  Vapor lock originated with the gravity feed fuel systems
> of the Model T era because what would happen is the gas would get
> close to boiling and bubbles would form in the fuel lines and try to
> go up as the fuel is trying to go down.  The result was a stalemate or
> what is known as vapor lock.
> 
> Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
> could ever have any effect on it.  

I've got a '72 MGB that would disagree. 
One can argue that since the fuel system of
a '72 MGB isn't much different from a '58 MGA,
the B doesn't classify as one of today's automobiles...

Anyhow, I've seen vapor lock on relatively new cars.
The conditions:  Hot day, clogged fuel filter,
and a quarter tank of gasohol.  With a full tank,
the problem would partly disappear (higher fuel pressure
at the tank).  Of course, a good mechanic would spot
the clogged filter in short order, and not mumble
mysticisms about vapor lock. :')

Jonathan E. Quist
Lachman Associates Inc.,
at AT&T Bell Laboratories
ihnp4!ihwpt!jeq

(Does anybody else out there dislike alcohol in your gas?)

In article<2922@vax4.fluke.UUCP> marauder@fluke.UUCP (Bill Landsborough) writes:
>Im sorry Randle but there is no such thing as "Vapor Lock" in today's
>automobiles.  Vapor lock originated with the gravity feed fuel systems
>of the Model T era because what would happen is the gas would get
>close to boiling and bubbles would form in the fuel lines and try to
>go up as the fuel is trying to go down.  The result was a stalemate or
>what is known as vapor lock.
>
>Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
>could ever have any effect on it.  
>
>Vapor lock tends to be the "scapegoat" when the mechanic can't solve
>the problem.  

WHOA there.  Want to come see it on my '83 Dodge Maxivan under load at
high altitide in hot weather?  The long under-car fuel line gets hot, 
vaporizes the gasoline and the fuel pump sucks vapor, not liquid.  Cool
the lines and the problem stops instantly.

I'll buy the "scapegoat" observation, but that isn't the same as saying
it can't happen!

FROM:   Brian G. Gordon, CAE Systems Division of Tektronix, Inc.
UUCP:   tektronix!teklds!cae780!gordon
	{ihnp4, decvax!decwrl}!amdcad!cae780!gordon 
        {nsc, hplabs, resonex, qubix, leadsv}!cae780!gordon 
USNAIL: 5302 Betsy Ross Drive, Santa Clara, CA  95054
AT&T:   (408)727-1234

In article <582@ihwpt.UUCP> jeq@ihwpt.UUCP (j quist) writes:
>> Im sorry Randle but there is no such thing as "Vapor Lock" in today's
>> automobiles.
... stuff about vapour lock (yawn :-)
>> Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
>> could ever have any effect on it.  
>
>I've got a '72 MGB that would disagree. 
>One can argue that since the fuel system of
>a '72 MGB isn't much different from a '58 MGA,
>the B doesn't classify as one of today's automobiles...

I also have a '72 B, but have never even had the slightest worry about
vapour lock. Mostly because I've never been able to get the fuel pump
to work for more than 20 consecutive minutes. Anyone want to buy a
slightly used, and *very* slightly functional fuel pump?

Trevor J. Smedley                    University of Waterloo

{decvax,allegra,ihnp4,clyde,utzoo}!watmum!tjsmedley

	Heres a major disagreement ! As a former GM tech , let me inform you
that vapor lock is alive and well and living in Z-28 Camaros with H.O. engines.
It occurs previous to the fuel pump , where the METAL fuel lines are close to
the exhaust system. On a hot day , take one of these things out and do several
good acceleration runs (like on an expressway ramp in traffic ) . Then when
you stop at a light and idle for about a minute , take off and try again.
You will RUN OUT OF GAS at about 3500 rpm in second gear. Let off the foot-feed
for a second and everything will be ok .
	IF you test the fuel pump pressure , you will find it to be ok .
If you check the fuel flow volume , you will find it more than sufficient. If 
you move the fuel lines away from the exhaust , it will cure the problem !
	Another nasty side effect of poor design is that the car will flood
and set a code 45 on the computer after being shut off HOT and restarted after
about 15 minutes . I have read fuel pressures that are excessive under those 
conditions , as the pressurized tank reaches 5 to 7 psi before the vent lets 
it escape , and then the efficient fuel pump drives it up the rest of the way.
	The float can't handle it , and the carb floods at idle. Again , moving
the fuel lines does it .


					tmorris@convex ,disclaim,disclaim !

> Im sorry Randle but there is no such thing as "Vapor Lock" in today's
> automobiles.  Vapor lock originated with the gravity feed fuel systems
> of the Model T era because what would happen is the gas would get
> close to boiling and bubbles would form in the fuel lines and try to
> go up as the fuel is trying to go down.  The result was a stalemate or
> what is known as vapor lock.

I have no doubt that that is when vapor lock was first seen but even 
vehicles with mechanical fuel pumps are sometimes prone to vapor lock.  Or
at least they used to be.  My brother has a 1942 Dodge Power Wagon (army
type) and he had to install an electric fuel pump because the mechanical
one would vapor lock when the engine got hot.  I think bubbles would collect
in the fuel pump so that the diaphram was pushing against bubbles instead
of against non-compressible gasoline.  Hence, no gas would get pumped.  It
seems like my old '61 Dodge pickup used to do that once in a while when I
was climbing hills too.  All this was at about 7000-10000 feet altitude
though so it may be different at sea level.

John Blankenagel

I have a 1953 Hillman Husky Wagon that I am trying to get to run.  I
think the problem might be as simple as a bad condenser.  The PROBLEM
is that the condenser is part of the base plate for the points and the
part is obsolete.  Does anyone out there know if I could drill out the
old condenser and replace it with one that is compatible and how do
I find out what condensers would be compatible?

Thanks in Advance,

Jim Raisanen

> Im sorry Randle but there is no such thing as "Vapor Lock" in today's
> automobiles.  Vapor lock originated with the gravity feed fuel systems
> of the Model T era because what would happen is the gas would get
> close to boiling and bubbles would form in the fuel lines and try to
> go up as the fuel is trying to go down.  The result was a stalemate or
> what is known as vapor lock.
> 
> Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
> could ever have any effect on it.  
> 
> Vapor lock tends to be the "scapegoat" when the mechanic can't solve
> the problem.  

What is a car of this day?  Porsche 914's of the 70's had vapor lock problems
that had to be fixed by the re-routing of the fuel line.  And a similar
problem occurs on the 1984/5 Trans Am, and Camaro Z-28 with the 5.0Liter
H.O. engine.  This problem cause GM to stop selling the HO engine.  The
GM problem is like vapor lock, but isn't exactly the same.  On warm days,
or in high altitudes, the carb has a fuel return line that open prematurly
because the gas vaporizes, thus encreasing fuel pressure, thus causing the
fuel starvation problem. I do realize that fuel starvation is a symptom
of vapor lock, but engineers can create the same problems with more hardware.

For anyone interested, owners of above said GM cars, the problem can be fixed
by GM (I think for free) by having them put a little fan on the carb to cool
the line to keep vapors to a minimum.  Other fixes are putting larger fans
that always run while the engine is running to keep the whole compartment
cooler, take off the trunk insulation, and put a plug in the fuel return line.
I don't suggest the last two, but I have had the last three done to my 84 TA
and the problem occurs about 1% as often as before.

					David Childs
					Integrate Solutions
"There's always time to scare the cat."

> Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
> could ever have any effect on it.  
> 
> Vapor lock tends to be the "scapegoat" when the mechanic can't solve
> the problem.  

What about the fuel line going to the fuel pump?  7-10 psi output pressure
says nothing about the input.

-Ron

In article <94400003@convex> tmorris@convex.UUCP writes:
>
>	Heres a major disagreement ! As a former GM tech , let me inform you
>that vapor lock is alive and well and living in Z-28 Camaros with H.O. engines.
>It occurs previous to the fuel pump , where the METAL fuel lines are close to
>the exhaust system. On a hot day , take one of these things out and do several
>good acceleration runs (like on an expressway ramp in traffic ) . Then when
>you stop at a light and idle for about a minute , take off and try again.
>You will RUN OUT OF GAS at about 3500 rpm in second gear. Let off the foot-feed
>for a second and everything will be ok .
>	IF you test the fuel pump pressure , you will find it to be ok .
>If you check the fuel flow volume , you will find it more than sufficient. If 
>you move the fuel lines away from the exhaust , it will cure the problem !

If you are talking about boiling gasoline in the fuel line, creating
air (or what ever byproduct comes of boiling gasoline), and having the
fuel pump try to pump that air, then I agree with you.  However the
misnomer of "vapor lock" is always blamed on the engine heat and its
ability to stop the gasoline dead in its tracks before it reaches the
carburetor.  Thats what people have been blaming automobile failure on
for years and if your mechanic tells you that you have vapor lock, you
should get a new mechanic.  
One could have, however, a sealed gas cap which prevents air from
replacing the gasoline in the gas tank as it is used.  As the vacuum
gets greater it finally overcomes the ability of the fuel pump to draw
fuel and you have a stalemate; until you remove the cap and then it
will run fine.

In article<2922@vax4.fluke.UUCP> marauder@fluke.UUCP (Bill Landsborough) writes:
>Im sorry Randle but there is no such thing as "Vapor Lock" in today's
>automobiles....

The fuel line from the gas tank to the fuel pump in my 1982 Dodge 024
is too close to the exhaust manifold and on hot days, after the engine
has been running for a while, the fuel boils out of the line when you
let the engine slow down to an idle.  You then have to wait about an
hour (the fuel lines are right on top of the manifold) to let the
pressure in the line drop enough for the fuel pump to overcome it.

That sounds like "Vapor Lock" to me.

					Leonard Bottleman
					RCA Cylix Communications
					ihnp4!akgua!cylixd!elf

All flames routed to the Engineering Group at Dodge.

> Im sorry Randle but there is no such thing as "Vapor Lock" in today's
> automobiles.
...
> Today's fuel pumps push fuel at a pressure of 7-10 psi and no bubble
> could ever have any effect on it.  
> 
> Vapor lock tends to be the "scapegoat" when the mechanic can't solve
> the problem.  

Maybe it doesn't qualify as a 'modern' automobile, but I was in
an old '53 Dodge pickup (in about '66) in the central valley of
California in the summer in 115 degree heat.  (That's in the shade
and there wern't no shade...)  The truck would run fine.  But if you
shut it off & sat so the heat built up, it wouldn't run.  The solution?
Put a wet rag on the long metal fuel line to the carb.  Ran fine.
That sounds like vapor lock to me.  The fuel pump may make 7-10 psi, but
it depends on a RAPIDLY running engine to do it.  Starting is another
matter...

Then again, our fuel may have a higher boiling point now than then.
(BTW, aviation gas is supposedly blended to avoid the lighter volitile
components of auto gas due to the potential for vapor problems.  Any
aviators out there who use auto gas care to comment?)

-- 

E. Michael Smith  ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems

'If you can dream it, you can do it'  Walt Disney

This is the obligatory disclaimer of everything. (Including but
not limited to: typos, spelling, diction, logic, and nuclear war)

In article <538@cylixd.UUCP> elf@cylixd.UUCP (Leonard Bottleman) writes:
>In article<2922@vax4.fluke.UUCP> marauder@fluke.UUCP (Bill Landsborough) writes:
>>Im sorry Randle but there is no such thing as "Vapor Lock" in today's
>>automobiles....
>
>The fuel line from the gas tank to the fuel pump in my 1982 Dodge 024
>is too close to the exhaust manifold and on hot days, after the engine
>has been running for a while, the fuel boils out of the line when you
>let the engine slow down to an idle.  You then have to wait about an
>hour (the fuel lines are right on top of the manifold) to let the
>pressure in the line drop enough for the fuel pump to overcome it.
>
>That sounds like "Vapor Lock" to me.
>
>					Leonard Bottleman
>					RCA Cylix Communications
>					ihnp4!akgua!cylixd!elf
>
How can fuel be stuck in an open ended tube?  As long as the fuel pump
has fuel and it is working right, and the float is not stuck, the
float bowl will call for fuel(because the float bowl is empty) and the
fuel will be delivered.  There is no Vapor Lock possible.  
   What does sound more likely in your case is a defective float bowl
needle and the fuel is forced past it and floods your engine so you
have to wait for an hour to start it.
I am finding that people are insisting on calling the inability for a
fuel pump to pump air as Vapor Lock, however the original Vapor Lock
was when gas bubbles would boil and FORCE the fuel to stop.  None of
the responses have talked about gas bubble FORCE.
I do agree that air in a fuel pump can stop gasoline delivery and that
gasoline can be boiled by hot exhaust pipes creating that bubble
before the fuel pump.  If you prefer to call that Vapor Lock then so
be it.
Bill Landsborough

 
----

"Love is patient and kind; love is not jealous or boastful; it is not 
arrogant or rude... Love bears all things, believes all things, hopes all
things, endures all things."   1 Corinthians 13:4-7

In article <2937@vax4.fluke.UUCP> marauder@fluke.UUCP (Bill Landsborough) writes:
>In article <538@cylixd.UUCP> I write
>>
>>The fuel line from the gas tank to the fuel pump in my 1982 Dodge 024
>>is too close to the exhaust manifold and on hot days, after the engine
>>has been running for a while, the fuel boils out of the line when you
>>let the engine slow down to an idle.  You then have to wait about an
>>hour (the fuel lines are right on top of the manifold) to let the
>>pressure in the line drop enough for the fuel pump to overcome it.
>>
>   What does sound more likely in your case is a defective float bowl
>needle and the fuel is forced past it and floods your engine so you
>have to wait for an hour to start it.

The first time this happened to me, I disconnected the fuel line 
going into the carb. and there was NO fuel at all.  I then turned
the engine over for a while, and still no fuel from the pump.  I
even went so far as to remove the gas filter, in case it was
blocked, but I still didn't get any fuel when I turned the engine
again.

>I do agree that air in a fuel pump can stop gasoline delivery and that
>gasoline can be boiled by hot exhaust pipes creating that bubble
>before the fuel pump.  If you prefer to call that Vapor Lock then so
>be it.
>Bill Landsborough

Ok, my car doesn't suffer from Vapor Lock, it suffers from gasoline
being boiled by hot exhaust pipes creating a buble before the fuel
pump :-).  It's still annoying!  I guess it serves me right for
buying a Dodge.

					Leonard Bottleman
					RCA Cylix Communications
					ihnp4!akgua!cylixd!elf

Sorry, direct mail wouldn't seem to go to your return address...

Received: by scgvaxd.UUCP (4.12/4.7)
From: ihnp4!scgvaxd!MAILER-DAEMON (Mail Delivery Subsystem)
Subject: Returned mail: User unknown
550 jimmmy... User unknown
Subject: Condenser Compatability

Hi Jim:

	The condenser associated with the points in a distributor is not a
very critical component.  Any part intended for this application that is
mechanically compatable should work fine.

	Also, the *only* way the condenser can keep the engine from running is
if it is shorted out.  An open condenser will cause excessive erosion and metal
transfer on the points, but the motor should still run.  There is not much
middle ground, except a part that only shorts out when it gets hot.
-- 
George Robbins			uucp:	{unirot|tapa}!grr
P.O. Box 177
Lincoln U, PA  19352	[The ideas herein are not responsible to themselves!]

In article <231@unirot.UUCP> grr@unirot.UUCP (George Robbins) writes:
>	The condenser associated with the points in a distributor is not a
>very critical component.  Any part intended for this application that is
>mechanically compatable should work fine.

The value of the cap is usually around .1 mfd; anything
in this order of magnitude should be fine... but ...

>       Also, the *only* way the condenser can keep the engine from
> running is if it is shorted out.  An open condenser will cause
> excessive erosion and metal transfer on the points, but the motor
> should still run.  There is not much middle ground, except a part that
> only shorts out when it gets hot.

I don't agree with this.  An open capacitor results in a
very weak spark; probably insufficiently hot to reliably
ignite the fuel mixture.  An ignition circuit is a basic
R-L-C combination (Resistor, inductor, capacitor) which has
a time constant and damping factor that ensures the stored
energy is dissapated at the plug.  If you reduce the C to
near-zero value the time constant is considerably shortened.
This results in the voltage building too quickly; it easily
sparks across the barely-opened points (resulting in the
excessive point erosion you noted).  In a correctly
functioning system the points are well open by the time
maximum voltage is created; in this case the spark plug is
the easier gap to bridge and the spark occurs there.

This is easily verified by experiment.  The next time you
are tuning up your non-electronic ignition car, try this:
Pull a plug (before touching the ignition) and crank the
ignition. (you might disconnect the other plugs so the
engine doesn't start).  Notice the nice, fat, blue spark.
Disconnect the condensor.  Now crank again and notice the
weak thin spark that is generated.

				Kevin
-- 
Kevin Szabo' watmath!watvlsi!ksbszabo (U of W VLSI Group, Waterloo, Ont, Canada)