Vapor Lock

[John N. Packard]

On the recently completed Sentimental Tour in Virginia I experienced hard starting due to vapor lock on the third day. Of several recommendations one was to attach a clothespin to the fuel line. I did this and the problem disappeared! Anyone have an explanation why? Or, what is your remedy for this problem?<P>jnp

[Guest]

John: Not sure what year your car is, but my Packard did the same thing - once. I checked the adjustment on the anti-perculation valves and found they were not opening when the car was shut off. After adjusting them to spec, never had a problem again.

[Rick Hoover]

John,<P>My dad tought me that trick many years ago. The wooden clothes pin absorbs the heat put onto the fuel line by the engine or manifolds, thus keeping the gasoline cool. <P>I would first try re-arranging your gas line futher away from the engine some. Or, you can install a insulation wrap on the line. If all fails, keep some pins in your glove box.<P>So how many pins did it take on the Packard? 4 or 6?<BR> <BR>Rick <p>[ 05-25-2001: Message edited by: Rick Hoover ]

[Guest]

I run 1 gal fuel oil to a tank of gas in my air cooled FRANKLIN and it runs great ........NEVER a problem with vapor lock ...try it

[Dave@Moon]

Wood is a terrible material for absorbing heat. I doubt the clothespin trick has anything to do with heat absorption. <P>More likely the effect is produced by the release of the fuel beyond the pressure prodiced by the clothespin, in effect producing a mini-evaporator. All materials cool when expanded, and the release of pressure on a liquid is a tried and true way to produce cooler conditions. <P>But then, I'm just guessing.

[John N. Packard]

Rick,<BR> Two pins did the trick because that was all I could locate amongst the AACA folks at Windmill Point! Upon reflection after arriving home I realized that I never replaced the sheet metal shield that the Packard engineers designed for this task when I replaced a leaky fuel line. Now I've got to find where I stashed it! I'm still amazed that the clothes pins seemed to work because of the poor heat conduction of wood. Dave, the line in question is a steel line; so I don't think expansion cooling is at work here.<P>jnp

[Guest]

I have been in this hobby for 40 years and have seen seen dozens upon dozens of pre WW II cars with clothespins on fuel lines. Some had just a few while others had so many that the fuel line was almost covered. Some had clothes pins holding a piece of aluminum foil all along the line. <P>Now, was it the clothes pins, the quantity of clothes pins or the aluminum foil that did the trick? The foil was a good insulator which probably did more good than the heat dissipation ability of clothes pins.<P>Is it an old wives tale, does it really work or what. I agree with part of Dave Moon's theory. Wood is a lousy conductor of heat so how could that solve the problem? The pressure thing is over my head.<P>If it is the clothespins, there MUST be some factor other than heat dissipation involved. I know --- it's magic. ~ hvs

[Guest Hal Davis (MODEL A HAL)]

Let me begin by saying I've never seen this done, but I've heard about it several times. I had always wondered if it was maybe vibration of the clothes pin on the steel line that burst the bubbles of fuel vapor in the line, but never discussed it with anyone.

[ply33]

Vibrations from the clothes pin makes as much sense as the other explanations.<P><span style="font-style: italic">Skinned Knuckles</span> magazine had an article (or series of articles) a few years back about things that can contribute to vapor lock.<P>One of the things mentioned was to have the fuel lines all smooth, no kinks or dents to trap bubbles. Also, make sure that there is a continious slope up from the pump to the carburetor. Any bubbles will then rise up the the carb and be expelled from the system. If the line dips down at any point there will be a high spot for the bubbles to collect and cause a problem.<P>I think someone else already mentioned making sure the factory heat shields are in place.

[fordee9r (Ron Springstead)]

Hey John,<BR>A while back, one of our members gave me an article on vapor lock from the national Pakard club's publication. Basically it tells how to install a fuel filter from a carbureted Chrysler K-Car with a return line.<P>They go into detail of how to hide this return line so you don't lose too many points if you show the car. They claim this is a permanent solution and, since it appeared in the Packard publication, it must be a common problem.<P>If you are interested, e-mail me and I'll send you a copy.

[The Old Guy]

Not knowing the compression in your Packard, I don't know if this is applicable or not ,but cutting the octane with fuel oil(2-3) gallons per tank will alleviate the problem. The older cars were made to run on 75 or so octane and will sometimes even run better<BR> Joe T <P>

[Guest]

HEY You guy's set me straight on the "FUEL OIL" you are adding to your gasoline, what kind fuel oil is it.ie Kerosene, Diesel fuel,<BR>JP-4, Heating fuel etc.<P>Bill Uhouse Pahrump NV.

[Guest]

Bill ~ I have used both kerosene and diesel fuel and found no difference. However I have never used more than 1 gallon per 15 gallons of regular gas. Kero is the most expensive, then diesel and lastly heating oil [no road tax]. Diesel is the easiest to get.<P>I would have probably used heating oil, but we only have wood and natural gas here at home. ~ hvs

[Guest]

Now that our "Government" is helping us live longer by making us use oxygenated gasoline in the summer, vapor locking will be a more common problem for many of us. The simplest solution is as HVS suggested, add a little diesel fuel with your gas. Kero will work and since it's refined higher on the refracting tower, it may not leave as many deposits on plugs. However, it is harder to find. Heating oil will be dyed red, but it's basically the same thing as diesel fuel. Watch the feds don't pull you over and take a sample out of your tank, like they do with trucks. Since there is no road tax on heating oil and the passing of the tax cut they may look where ever they can for revenue. Just kidding, I'm sure they won't check gasoline powered vehicles.

[Guest]

I was once told that the effect that clothes pins have is to act as a air diverter vane, causing more airflow along the steel line which carries off a greater amount of heat or acts as a baffle to divert heated air away from the line. Makes as much sense as any of the other explainations I've heard. Whilst on a gasolene topic, octane rating has NOTHING to do with the available heat energy contained in a gallon of gasolene, hence a gallon of regular has the same energy value as a gallon of SUPER-DUPER. What's the octane rating for? Actually octane modification additives cause the combustion process to slow down, thereby causing a slower rise in the peak combustion pressure. If your engine parameters and design doesn't require a high octane rating fuel, don't use it. By doing so you could experience engine over-heating and poorer fuel mileage, as well as a decrease in engine performance. Recirculation of fuel back to the tank, something that's currently being done in new production, and has been done for many years, is a sure-fire way to eliminate vapor lock.

[Guest]

The best way to rid vapor lock, and hard starts when the engine is hot, is to install an electric fuel pump back by the gas tank. I have a 39' Packard, 1404 model, it's all stock right down to the 6 volt battery, I've installed one when I first got her, and have never had the problem. The way I have it set up is, tank> filter> electric pump> and then it connects to the stock fuel line.

[John N. Packard]

A lot of good information here; but I have a confession to make! Upon closer inspection of my '54 Packard I discover that I failed to replace the heat shield between the manifold and the fuel pump. I removed it to repair a leaky fuel line and never put it back. I suspect that Packard engineering (Quality First) installed that shield for a purpose! However, the clothespins did seem to work. <P>jnp

[D Binger]

Three cheers for the clothes pins.<BR>

[countrytravler]

It's getting to be that time of year again. Share your stories. Any since this thread was cut off onJune 2001?

 

Since wood is a poor conductor of heat, they shouldn't work. That's why BBQ pits have wooden lid handles. Unless you're using metal clothespins.

 

[jp928]

Vapor lock is almost always caused by relatively high pump sucking fuel upwards. As soon as the suck depression vaporizes the fuel there you are - some of the worst are English cars with SU pumps high on the firewall. Solutions - site the pump as low as possible , close to the tank; reduce fuel temp - paint the bottom of the tank silver or white, if exposed to the road to reduce heat uptake. Best solution as above is an electric pump down at the tank.

 

jp 26 Rover 9, High tank, gravity feed.

 

PS Did you know that gravity feed from a wing tank is enough to keep a jet engine running! Look up QF32 , 2010.

[cahartley]

In my mind the only plausible reason a wood clothes pin could have any effect at all is perhaps it disrupts air flow in that area which would contribute to increased cooling?

[Rusty_OToole]

Today's fuel is made for fuel injection engines. They don't pay any attention to vapor lock. Old fuel was low octane and contained more heavy ends or oily substances. Diesel fuel actually contains more energy than gasoline because of this. Old, long stroke low compression engines will run better and cooler and produce more power on low octane fuel. You can duplicate this by adding stove oil, kerosene, or diesel to the gas. Stove oil or kerosene is lighter and less smelly but diesel is easier to get. Diesel and home heating fuel are the same thing.

 

Have heard of adding up to 25% kerosene for an old Buick with 4.5:1 compression.  For an engine with 6 or 7 to one, I would start with 10%.

[jrbartlett]

Rusty -- In my view you are both right and wrong. Old long-stroke engines don't run better on lower-octane fuel per se, because octane doesn't measure energy content -- it measures anti-knock capability. Old engines simply don't need the high octane found in modern gasoline, but all else being equal won't run less well on high octane fuel. But old engines can run better with, as you say, some of these other fuels mixed in with the gasoline because of two reasons. Because these other fuels are "heavier," they 1) reduce the volatility of the mix and thus reduce the risk of vapor lock, and 2) increase the Btu content of the mix. Kerosine contains 135,000 Btus per gallon; diesel and heating oil contains 136,000 Btus; while gasoline contains only 124,000 per gallon. So you are upping the energy content of the fuel. Of course you can only go so far, as the mix still has to be capable of being fired by a spark plug.   

[Spinneyhill]

I wonder if vapor lock is perhaps more prevalent today than in the past because fuels have a higher fraction of "aromatics" that evaporate more readily than fractions in older low octane used to? There was controversy in NZ a few years ago because rather than a "balanced" fuel, a company was adding imported aromatic fractions to raise the octane rating. It evaporated quickly. This was a cheap way to make high octane fuel.

 

Does vapor lock occur more or less readily using fuel containing ethanol?

[Rusty_OToole]

I believe the heavier fuels like kerosene or diesel also burn slower which is better for a slow revving long stroke engine. Long stroke engines first became popular around 1915 when fuel quality reached a low ebb. In response to the overwhelming demand for gasoline the oil companies mixed heavier elements with their fuel. Previously car engines were square or nearly square, a 4" bore and 4 1/4" stroke being typical. Then they went to a 3" bore and 5" stroke to get the power out of the slower burning low octane fuel.

[C Carl]

JIGGERS !!!! Here come the Octane Police ! I have to run and hide ! While I am gone , please read the short paragraph above the distillation curves shown in the bottom pic. This from "Marks' Mechanical Engineers' Handbook" , 2nd. Ed. , 1924. Also from "Marks'......." 3rd Ed. , 1930 , shown in the middle pic, please read the paragraph to the left of the distillation curves. This will explain the degradation of gasoline from the mid or late 'teens , and finally a recovery similar to the very good gasoline available until the mid 'teens. The distillation curves in the top pic are from "Marks'......." 6th Ed. , 1958 . Now , octane in 1920 was around 40. By the end of the '20s , around 50. Engines of the time were perfectly matched to the gasoline available , as the Octane Police will teach us. Low compression long stroke engines must use LOW octane gasoline because it burns FASTER ! Huh ? Yup ! HERE THEY COME ! Gotta lay low for a while. Let me leave you with this : Octane refers to flamefront propagation rate under standard conditions. The higher the octane , the slower the flamefront propagation rate.  Hiding out , - Carl

 

Edited April 7, 2017 by C Carl
Add content (see edit history)

[ply33]

13 hours ago, Spinneyhill said:

Does vapor lock occur more or less readily using fuel containing ethanol?

 

It is my understanding that adding ethanol to gasoline raises the vapor pressure, that is it makes it more likely to vaporize and thus more likely to cause delivery issues in a low pressure carburetor type fuel system. https://duckduckgo.com/?q=effect+of+ethanol+on+gasoline+vapor+pressure&bext=msl&atb=v45-6&ia=web

[jp928]

I thought Octane referred to a fuel's ability to resist knock, or pre-ignition, hence the higher the compression, the higher the octane required.

??

 

jp 26 Rover 9

[zeke01]

Don't forget that 90% of fuel problems are electrical in nature. Check your coil and condenser. Zeke

[PFitz]

I thought Octane referred to a fuel's ability to resist knock, or pre-ignition, hence the higher the compression, the higher the octane required.

??

 

jp 26 Rover 9

 

-------------------------------------------------

 

Yes, it is.

 

For additional info on that look up what the term "anti knock index" means.  Sometimes seen on gas pumps as "AKI".

 

There's lots of info on octane rating verses flame propagation speeds, too. Here's just a bit of some of the explanation available.

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=967599

 

Paul

Edited April 9, 2017 by PFitz (see edit history)

[C Carl]

BRAVO , PAUL !! Thank you very much for alerting us/me to the Gasoline FAQ. Reading all 4 parts is extremely interesting. I have already learned quite a bit , but this will require considerably more study on my part. Have any of you guys read all of this ? Are any of you engineers ? I already have two major conflicts between prior knowledge and what I have learned so far. I have been curious about aspects of octane/flamefront propagation rate for decades. I cannot reconcile previous long held understandings with this marvelous new information. Very difficult to argue with anything in this well written document. Therefore, as with any learning process, this has stimulated questions brewing up in my mind. I hope you guys will be able to answer what I may not be able to answer myself. I think that will be the only way the Octane Police will let me make bail ! By the way : are any of you guys old flight engineers going back 50 years or so to the days of recip power ? Also , Paul , do you have any other links to octane/flamefront rate ? Thanks again for the fascinating read !  - Carl

[PFitz]

C Carl.

 

Your welcome. There is a lot of info if you do a web search using the search term, "octane and flame front propagation".

 

Keep in mind that todays gasoline is not the same as that from decades ago.

 

With all the additives there is not much "gasoline" in today's gas.  And additives can not only change octane rating, they can affect flame front propagation. So discussions of flame front based on old texts are not really relevant  to what we can get at the gas pump, except to have a debate to chew on.  

 

Plus, octane rating is not the only thing that affects flame front propagation. Turbulence inside a combustion chamber, plus combustion chamber shape can also affect how a flame front can react. 

 

I would love to have some drums of fresh 57 octane gas from the late 1920's, plus some 1930 Sunoco Blue 70 octane, to try out on my customer's cars to see what they really ran like when new. We can restore them mechanically to showroom new, but we can't restore what comes out of the gas pumps. And that has a big affect on how they were originally designed to run.

 

As you know, a lot has changed in the automotive chemical world in 90-100 years. Some things still apply and some don't. The trick is in don't assume everything they knew back then was the end-all be-all of automotive engineering knowledge.  And conversely, don't assume that all "advancements" we've made are across the board best for antique cars.     

 

Paul  

Edited April 11, 2017 by PFitz (see edit history)

[cahartley]

I had a 1935 Oliver Hart Parr 70 tractor.

Designated 70 because it was rated to develop its horsepower with 70 octane gasoline.

The Continental 6 cylinder engine had fairly high compression for the time.

I skidded quite a few logs with it and it needed to work pretty hard going up hills in our woods.

I never used anything other than 97 octane gas in it and it ran perfectly.

If I had to guess it probably ran better than it would have with 70 octane gas.

I DO know it dynoed 30 horsepower so....... 

Edited April 12, 2017 by cahartley (see edit history)