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Not vapor lock!


Guest imported_V12Bill

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Guest imported_V12Bill

For some time now I have been experiencing hard restarts on a hot engine. I have chalked it up to nature of the beast,- vapor lock. This past weekend while out for a ride my Lincoln began to miss and lose power and finally it died on the road.One of the many things I checked was the spark at the plug while turning the engine over. I got a weak spark (1/l6 arc) on most plugs and a few with no arc. I had the coil off the car while checking the rotor and points and having found no obvious cases for my dead V 12 I replaced the coil and tried to start the engine one last time before calling for a tow truck. Lo and behold the engine fired up , was running strong and appeared ready to take me home.

I almost got home and the engine started to miss and sputter again. I made it home on an engine that was getting ready to let me down again. I checked the arc at the plugs again, and again I had a very weak spark on most plugs and none on a few more.

The next day I replaced the coil with an other that I had and retraced my path from the previous day. The engine ran very strong for the entire route. I got home and checked the arc at the plugs and now got a spark of 3/l6 to 1/4 inch. This is now what I should have had all along.

I had failed to recognize the coil as a possible source of trouble because it was a rebuilt from A & S.

Besides a weak arc and hard restarts. I had also noticed that the engine would not idle at a low speed, It faltered when starting from a dead stop and the gas mileage was down.

If you have what you think is vapor lock , don't overlook the coil as a possible culprit.

Bill crazy.gif

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So often the culprit Bill, Vapor-lock is very rare, and unless everything is super hot on a scorcher day, unlikely, as V-L is caused by the gasoline actually boiling, the cure used to be to put a big wet squishy piece of fruit over the fuel pump. Bad coils are an increasing problem as these coils get older and older, just like us, but fortunately they can be rejuvenated, never heard of a rebuilt cashing in before, that is scary. On a related matter, Jack never told us how his condenser search came out, but some investigation has shown that '42-'48 Ford condensers have the same specs as our Lincolns, the attaching tabs have to be modified, but otherwise they are the same, glad you are running good now, and thanks for sharing the saga, Rolf

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  • 4 weeks later...

The condensors I used were from a 48 ford, had to change the mounting tab but havent had a problem since. the water pumps from Skip has helped allot with my cooling problem. sorry I havent wrote sooner been stuck in Oklahoma, will be home next monday and looking forward to some rest, 2 year old twins have more energy than my 69 charger 440 R/T. im worn out and Loving it.

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">So often the culprit Bill, Vapor-lock is very rare, and unless everything is super hot on a scorcher day, unlikely, as V-L is caused by the gasoline actually boiling, the cure used to be to put a big wet squishy piece of fruit over the fuel pump. Bad coils are an increasing problem as these coils get older and older, just like us, but fortunately they can be rejuvenated, never heard of a rebuilt cashing in before, that is scary. On a related matter, Jack never told us how his condenser search came out, but some investigation has shown that '42-'48 Ford condensers have the same specs as our Lincolns, the attaching tabs have to be modified, but otherwise they are the same, glad you are running good now, and thanks for sharing the saga, Rolf </div></div>

Vapor Lock is not at all unusual, certainly with cars the vintage of a Lincoln V12. The gasoline doesn't need to be boiling (and when you think of it, if the gasoline were literally boiling in your fuel line, vapor-lock would be the least of your worries!)/

The old diaphragm fuel pumps, such as were all but universal on American cars from the early 30's until the advent of fuel injection systems in production cars over the past 25 or so years, serve to draw or "pull" the fuel from the tank, down a fairly long, and not at all large line from the tank. This has the effect of actually dropping the pressure of the fuel behind the pump itself below atmospheric pressure, which allows it to vaporize much more readily than it would at even normal atmospheric pressure (BTW, this principle is also the root cause of much of the overheating troubles of Ford flathead V8's through 1936, with their water pumps designed to exhaust heated water from the front of the cylinder head, lowering the ambient pressure of already hot water, to the point that steam pockets could and did appear, and the engine simply boiled over right then and there), which coupled with the heat from the engine, the exhaust system and coming off hot pavement made the vaporizing even more likely.

A diaphragm fuel pump needs fuel in it, physically, in order for it to work--have an air or vapor bubble large enough in the line back to the tank, it simply won't move anything at all.

Vapor Lock is self-curing. As soon as the fuel in the line cools down, it condenses back to a liquid, fills back in the offending bubble of vapor, and the fuel pump functions again.

But yes, vapor lock is a lot more common than most might think--but the sure check for it is to see if the engine starts and runs once cooled down.

Art

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