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Hot running problem - Vapor lock?

Posted By peeeot 15 Years Ago
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peeeot
Posted 15 Years Ago
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In the late summer heat, my '59 Galaxie has sometimes acted up at traffic lights.  As long as I am cruising, or usually even rolling, it does great.  The most common form this problem has taken will involve driving for about an hour non-stop with no problems of any kind, and then the first traffic light I come to and have to sit at it will either stall at the light after a while (idle quality breaks down first) or else it will stumble or stall when the light turns green.  Sometimes it is hard to start it when it stalls, but usually I can start it back up quickly. 

I haven't had issues for a while but today when I came off the highway exit ramp and accelerated into traffic it was acting like there wasn't enough fuel in the bowl--stumbling if I gave it anything more than light throttle.

Once it starts misbehaving, it will not fail to stall out if you let it idle long enough, even with the hood open and air cleaner off idling in park.  I have done this a few times, even taken the air horn off and watched the fuel coming into the bowl.

Now, I am inclined to think I am dealing with partial vapor lock for two reasons: 1. idling with the air horn off, it is audibly clear that there is about as much vapor as liquid gas coming out of the fuel inlet needle. 2.  Looking in the glass filter bowl on the fuel pump, you can see bubbles at the top, large and small, and quite active.

I am not certain that's the problem, though, because at the time the engine dies while idling with air horn off, there is still plenty of fuel in the bowl; indeed, it is within a 32nd or so of the spec'd fuel level.

Any ideas?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

oldcarmark
Posted 15 Years Ago
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I have a similar problem with mine.When the outside air is in the 80's and 90's and high humidity as we have had many days here in Ontario this summer,the idle quality definetely changes-for the worse.This last week or so with temps in the low 70's and very little humidity it runs great at idle-even hot.Idle seemed to improve when I removed the air delector on top of the rad as I learned on this site,was designed to keep hot air IN the engine compartment so the carb didn't freeze up in winter. I have the clear glass bowl fuel filter and gas is flowing fine it looks like.I will be following this topic for more input.

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lovefordgalaxie
Posted 15 Years Ago
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Is your carb an Autolite 2100?

If so, I had the same problem once. The culprit was the power valve at the bottom of the bowl. That thing was leaking gas, and the engine was running too rich. Rich enough to die at idle, and being difficult to start. A new one kiled the problem. The odd thing was that the only indication of the bad power valve was this.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec
oldcarmark
Posted 15 Years Ago
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If you suspect the power valve turn both  idle mix screws in lightly seating them.The motor should die.If it continues running suspect the power valve allowing fuel to keep the motor running.

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peeeot
Posted 15 Years Ago
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I do have an autolite 2100.  I'm not certain, but I think I tried turning the mixture screws in; I'll try again to be sure.  It has been close to 2 years since I rebuilt the carb.  I am not sure how long such parts are expected to last.

One thing I'm wondering: if the power valve were leaking, why wouldn't the problem be evident all the time?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

lovefordgalaxie
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That's because when you are cruising, or driving a little faster, there is not the same amount of vacuum to "pull" the gas trugh the power valve.

The leak can be trough the tread of the valve and gasket, and not the membrane, so, the temperature of the carburetor's body can make it worse when the engine is hot.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec
peeeot
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You were quite right!  I was able to turn the mixture screws in to 1/4 turn from seated and still run at about 450 rpm.  I removed the cover from the power valve and found gas in it.  The culprit is the gasket; I tested the diaphragm with a vacuum pump and it is fine.  I recalled then that the gasket is really old; when I rebuilt the carb, the new gasket was too large so I reused the old one. 

I will be replacing the gasket promptly and will report the results later.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

lovefordgalaxie
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Very good that you found the problem! And a cheap one to fix.Smile

Now that you have the carb out, take a look at the play on the axle. If it's too much, it can alow air to get in, and also cause the engine to die at idle, but in this case, only when very hot. I never saw a carb with that much play, but my Ford Galaxie Service Manual talks about this as a secondary cause to the problem.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec
Ol'ford nut
Posted 15 Years Ago
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lovefordgalaxie (9/7/2010)
Very good that you found the problem! And a cheap one to fix.Smile
Now that you have the carb out, take a look at the play on the axle. If it's too much, it can alow air to get in, and also cause the engine to die at idle, but in this case, only when very hot. I never saw a carb with that much play, but my Ford Galaxie Service Manual talks about this as a secondary cause to the problem.

By "axle" I believe he means the throttle plate shaft. You can get play where it goes through the body and it will suck air. I had one carb that bad so I took out the shaft and drilled indent in body to accept a o-ring around shaft. IT WORKED!

Ol'ford nutCentral Iowa

56 Vic w/292 & 4 spd.

lovefordgalaxie
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Ol'ford nut (9/7/2010)
lovefordgalaxie (9/7/2010)
Very good that you found the problem! And a cheap one to fix.Smile

Now that you have the carb out, take a look at the play on the axle. If it's too much, it can alow air to get in, and also cause the engine to die at idle, but in this case, only when very hot. I never saw a carb with that much play, but my Ford Galaxie Service Manual talks about this as a secondary cause to the problem.




By "axle" I believe he means the throttle plate shaft. You can get play where it goes through the body and it will suck air. I had one carb that bad so I took out the shaft and drilled indent in body to accept a o-ring around shaft. IT WORKED!




Yes!! That's exactly what I mean. Around here, we just cal it axle.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec


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