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Vapor Lock V-12


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For the second time this show season my 48 LC with V-12 vapor locked leaving a show. Very embarrassing <img src="http://forums.aaca.org/images/graemlins/blush.gif" alt="" />!!!..I've been told that the best cure is an electric fuel pump. I'm hestitant only from an orginality standpoint but clearly I do not want to be hand pushed to a start again. I did have Skip Haney rebuild the waterpumps, so the engine does run cooler. Is there something elese I can do to prevent the vapor lock? I would really appreciate your insights.

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The term "Vapor lock" is an old wives tale. What you have is really "fuel pump body thermal (heat) distortion". The pump halves heat up and warp, breaking the "prime" of the pump. This is due to overtightening of the pump halves, distorting the screw hole bosses.

Remove the fuel pump from the engine. Disassemble the two halves of the pump body. you will find that the mating surfaces of the pump body halves are warped where the screw holes are located. get a flat file, or sheet of emery on a piece of glass and carefully "flatten" the two halves, being certain to remove material evenly. While you are at it, contact the antique auto parts cellar and get a fresh kit. When you re-assemble the pump, be very careful to tighten the screws evenly, and enough to hold it together, but not enough to re-warp the housings.

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"Vapor Lock" is indeed extremely rare. Another possibility is deterioriation in the short rubber section of fuel line on the inlet side of fuel pump, case distortion as described above, leaky or cracked diaphragm in the fuel pump, or a worn fuel pump pushrod. Putting an in-line "primer pump" only covers up your real problem. Check for vacuum leaks around the various fittings on the intake manifold, they can cause problems with fuel delivery too. (I found a leak in my windshield wiper motor vacuum hose that when fixed really made a difference at idle and low RPM, especially hot)

post-31357-143137898149_thumb.jpg

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">"Vapor Lock" is indeed extremely rare. Another possibility is deterioriation in the short rubber section of fuel line on the inlet side of fuel pump, case distortion as described above, leaky or cracked diaphragm in the fuel pump, or a worn fuel pump pushrod. Putting an in-line "primer pump" only covers up your real problem. Check for vacuum leaks around the various fittings on the intake manifold, they can cause problems with fuel delivery too. (I found a leak in my windshield wiper motor vacuum hose that when fixed really made a difference at idle and low RPM, especially hot) </div></div>

Rare in some cars perhaps, but not at all uncommon with any Ford, Mercury or Lincoln flathead V8/V12, due to the placement of the fuel pump on top of the engine, all the way to the back, just in front of the firewall, which is the hottest area of any engine compartment. This meant that gasoline had to be sucked upward almost 18" from the horizontal run of the fuel line, the fuel line necessarily feeling the heat output of the exhaust system as well. That, coupled with the ordinary hot-running characteristics of these engines, made vapor lock a regular operating feature.

When Ford Motor Company finally moved the fuel pump to a more conventional location on the lower front right side of the crankcase, the problem pretty much went away--however, vapor lock was always a possibility with mechanical diaphragm fuel pumps that were called upon to draw the gasoline several feet from the tank, particularly in very hot weather.

Art Anderson

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Dear Art,If you go to any Ford V-8 websites there is ALWAYS something regarding flatheads be they 8s or 12s quitting in the heat.The reasoning goes anywhere from vapor lock to coil trouble to new fuel formulation.The true test is to throw some ice cubes into a plastic baggy and place the bag around the fuel pump.In MOST cases it ends up being the coil.Everything you said regarding fuel pump placement by Ford and Lincoln is true.Take care.diz <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />

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If you want a cheap and easy fix from "back in the day" just clamp on a series of wooden clothes pins on the steel part of the fuel line near the carb

Another urban myth from "back in the day". The clothspin supposedly act as a heat sink, drawing the heat from the fuel line. Wood is a lousy conductor of heat and the benefits are negligable at best.

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I discussed this with an old car guy, now deceased, who ran a service station when I was a teen ager. He recalled that when he was young they would cut a grapefruit in half and press it down onto the fuel pump. He didn't know how effective it was but it made them feel like they were big time auto experts and seemed to work.

Rollie

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Vapor lock is a real problem when the car is not moving fast enough to provide enough air flow to keep the fuel lines cool.

I know a guy who had a Packard twin six that was the only one at the national meet that could actually drive his car on a hot day. His solution was to install and electric fuel pump with a bypass line at the carburator to keep cool fuel flowing constantly.

Mark Shaw

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  • 1 month later...

Firstly I would like to state that the phrase ?Vapor Lock? is a misnomer and doesn?t exist. Vapor by its very nature can?t lock anything. The proper or more accurate is Percolation, anyone who has used an old percolator coffee pot knows about this! It doesn?t make any difference whether it is in the carburetor or the fuel pump. The fuel is boiling. This is due to the lighter portions of the fuel boiling and forming a gas which pushes the heavier parts of the gasoline into the other parts of the carburetor and flooding the engine. Other things can happen also which I will let your imagination run wild. In my case just putting an electric fuel pump on the gas line close to the fuel tank cured the whole problem. Some carburetors even have a special Anti-Percolator adjustment to help prevent Percolation; an example of this is in my old Motor Manual on Carter Carburetors.

The fuel pump being in an exceptionally hot place in the engine area doesn?t help the situation either. Old Ford V-8s were famous for this. Wearing of the pump rod and lack of lubrication of the fuel pump was another cause as there just wasn?t enough stroke of the pump to pump fuel. Also the low pressure area on the suction side of the fuel causes the fuel to have more of a tendency to ?Boil or Percolate?. I have never had any problems with coils so therefore I know little or nothing about that condition, although I can easily see it happening. M.L. Anderson

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Firstly I would like to state that the phrase ?Vapor Lock? is a misnomer and doesn?t exist. Vapor by its very nature can?t lock anything. The proper or more accurate is Percolation, anyone who has used an old percolator coffee pot knows about this! It doesn?t make any difference whether it is in the carburetor or the fuel pump. The fuel is boiling. This is due to the lighter portions of the fuel boiling and forming a gas which pushes the heavier parts of the gasoline into the other parts of the carburetor and flooding the engine. Other things can happen also which I will let your imagination run wild. In my case just putting an electric fuel pump on the gas line close to the fuel tank cured the whole problem. Some carburetors even have a special Anti-Percolator adjustment to help prevent Percolation; an example of this is in my old Motor Manual on Carter Carburetors.

The fuel pump being in an exceptionally hot place in the engine area doesn?t help the situation either. Old Ford V-8s were famous for this. Wearing of the pump rod and lack of lubrication of the fuel pump was another cause as there just wasn?t enough stroke of the pump to pump fuel. Also the low pressure area on the suction side of the fuel causes the fuel to have more of a tendency to ?Boil or Percolate?. I have never had any problems with coils so therefore I know little or nothing about that condition, although I can easily see it happening. M.L. Anderson </div></div>

Except that "boiling", be it water or gasoline, creates a vapor, as opposed to a liquid--and, any pump that is not positive displacement (as in either piston pump or rotary gear -- such as a Rootes pump) such as the diaphragm pumps which constitute most fuel pumps in older cars simply will NOT propel a vapor--hence the vapor simply "locks" the fuel flow in those old systems until liquid gasoline displaces the vapor at the pump itself.

And, even percolation is an incorrect term here, as percolating refers to the flow of liquid through another medium, such as water through coffee grounds, or rainwater (or other nastier liquids) flowing or seeping downward in the ground.

Art

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How is it that Ford Motor company--a (then)major world producer of automobiles, at the low and high end of the market place lacked the scientific moxie to solve this (apparent-supposed)"vapor lock" issue on its flathead V-design engines? I could understand one, maybe two years worth of this problem, then a fix that could be reto-fitted onto exsisting units (but then, I came up around GM products, a company that has always prided themselves on a firm scientific-research foundation, at least back when). But more than ten years worth of product that shuts itself down due to heat?--that seems almost British (dampness or moisture is their enemy). Has anyone ever tried to simulate this supposed phenominon? inseterted a glass view tube in the fuel line to see if the fuel is liquid or gas (vapor)?

It has never made sense, and those that believe have somewhat of a blind faith in the phenomonon. I like to reduce unknowns by tests, and get numbers on things to correlate responses. Have any FoMoCo flat head gurus done this?

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Arthur E. Anderson states;

And, even percolation is an incorrect term here, as percolating refers to the flow of liquid through another medium, such as water through coffee grounds, or rainwater (or other nastier liquids) flowing or seeping downward in the grounds.

I?m glad you put the word ?locks? in parentheses as the word I used is written/used in the Motor?s Manual 1958. The dictionary defines percolation as you state but I guess even the motor Manual people couldn?t come up with a better word. I believe that what they meant is the boiling vapor process as opposed to the have the coffee ground in place as the old lousy percolator still do the action whether or not the grounds are in place. And the liquid is under a small amount pressure to force the hot water up the tube and over the area where grounds are placed. Actually I believe we need a better word in any case.

Yours truly, Marion L. Anderson

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The end of this story is simply, I had the electric fuel pump installed, in my 48 Lincoln Connie V-12 and have not had a problem since with VAPOR lock. Equally impressive is that even after she sits awhile, between car shows, pre electric pump there was a lot of starter turning til the fuel hit the carb. Now with a mere flick of a switch, a few seconds, hit the starter button and she fires right up. Wish I had it installed several years ago, would have saved a lot of aggravation.

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The end of this story is simply, I had the electric fuel pump installed, in my 48 Lincoln Connie V-12 and have not had a problem since with VAPOR lock. Equally impressive is that even after she sits awhile, between car shows, pre electric pump there was a lot of starter turning til the fuel hit the carb. Now with a mere flick of a switch, a few seconds, hit the starter button and she fires right up. Wish I had it installed several years ago, would have saved a lot of aggravation. </div></div>

Pretty much like any car with an electric fuel pump pushing the fuel to the carburetor (or for that matter, a modern car with EFI).

Art

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">How is it that Ford Motor company--a (then)major world producer of automobiles, at the low and high end of the market place lacked the scientific moxie to solve this (apparent-supposed)"vapor lock" issue on its flathead V-design engines? I could understand one, maybe two years worth of this problem, then a fix that could be reto-fitted onto exsisting units (but then, I came up around GM products, a company that has always prided themselves on a firm scientific-research foundation, at least back when). But more than ten years worth of product that shuts itself down due to heat?--that seems almost British (dampness or moisture is their enemy). Has anyone ever tried to simulate this supposed phenominon? inseterted a glass view tube in the fuel line to see if the fuel is liquid or gas (vapor)?

It has never made sense, and those that believe have somewhat of a blind faith in the phenomonon. I like to reduce unknowns by tests, and get numbers on things to correlate responses. Have any FoMoCo flat head gurus done this? </div></div>

It's pretty basic public school science class stuff, mrpushbutton--no great effort at scientific observation is needed. Gasoline, just as any other liquid, cannot be compressed in volume significantly, but gasses (such as gasoline vapors) can. Diaphragm fuel pumps to don't have the ability to compress gaseous vapors, but can compress, or pump liquids. Gasoline boils (or vaporizes) at temperatures much lower than water, so the heat of an engine bay can cause it to boil, or vaporize in the fuel line leading up to the fuel pump. And, BTW, vapor locking was not at all limited to flathead Ford V8's--it could, and did, happen to any make of car using diaphragm mechanical fuel pumps mounted on the engine--it's just that it happened with far greater regularity on a Ford V8 or Lincoln V12, due to the high mount location of their fuel pumps, and a fuel line that had to travel upwards at least a couple of feet to the top of the engine, to reach that fuel pump.

Vapor lock was a pretty regular occurrence, and certainly no "phenomenon".

Art Anderson

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The term "Vapor lock" is an old wives tale. What you have is really "fuel pump body thermal (heat) distortion". The pump halves heat up and warp, breaking the "prime" of the pump. This is due to overtightening of the pump halves, distorting the screw hole bosses.

Remove the fuel pump from the engine. Disassemble the two halves of the pump body. you will find that the mating surfaces of the pump body halves are warped where the screw holes are located. get a flat file, or sheet of emery on a piece of glass and carefully "flatten" the two halves, being certain to remove material evenly. While you are at it, contact the antique auto parts cellar and get a fresh kit. When you re-assemble the pump, be very careful to tighten the screws evenly, and enough to hold it together, but not enough to re-warp the housings. </div></div>

Then, why would this have happened with brand-new cars, having brand-new, never-before-disassembled or repaired fuel pumps? Sorry, but I can't buy this one--having grown up around such cars when they were brand-new.

Art Anderson

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There are other things that do the same thing as "Vapor Lock" possibly Coil, Capacitor, Fuel Pump Weakness or complete failure. My experience was on an old Dodge RedRam V-8 1953 in the dead of summer in Kansas City Mo. in about 1958.. After installing all I had to do was hear the fuel pump (Autopluse) go click click several times until it stopped then turn the key to start and it never failed to start after the Autopluse was installed.

Marion L. Anderson

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In addition the the previous;

Motor Manual 1958 define ?Vapor Lock? as follows.

The term vapor lock means the flow of fuel to the mixture chamber in the carburetor has been stooped (locked) by the formation of vaporized fuel pockets or bubbles caused by overheating of the fuel by hot fuel pump, hot fuel lines or a hot carburetor.

The more volatile the fuel the greater the tendency for it to vapor lock. Vapor lock is encouraged by high atmospheric temperature, hard driving, defective engine cooling and high altitude.

A mild case of vapor lock will cause missing and hard starting when the engine is warm. Somewhat more severe vapor lock will stop the engine which cannot be started again until it has cooled off enough so the vaporized fuel has condensed to a liquid.

Marion L. Anderson

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I maintain that it's a pretty sad commentary on Ford to have made a product for over a decade that can't handle getting hot. Notice that all of the old country boy fixes involved putting ice bags, grapefruit halves, whatever on the FUEL PUMP--not the fuel lines. as for the clothes pins, you might as well have taken the car to a faith healing service or called in a witch Doctor.

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