# vapor lock or flooding



## TCone (Jul 4, 2021)

once car warms up hot especially after sitting in traffic stumbles wants to die after leaving the light lowered float levels Holley carb have not checked fuel pressure


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## Sick467 (Oct 29, 2019)

Sounds like it could be vapor locking. Take some aluminum foil and loosely wrap the fuel line from the pump to the carb as a temporary test. Loosely wrapping it is the key...it's more of a crumple wrap that leaves as much air in the wrap as possible while getting the foil to stay on the line. This will help insulate the line from the heat. If the problem goes away with the foil...it's vapor locking in the line.


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## An0maly_76 (Dec 25, 2021)

If not vapor-locking, possibly heat causing coil or point breakdown.


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## TCone (Jul 4, 2021)

Sick467 said:


> Sounds like it could be vapor locking. Take some aluminum foil and loosely wrap the fuel line from the pump to the carb as a temporary test. Loosely wrapping it is the key...it's more of a crumple wrap that leaves as much air in the wrap as possible while getting the foil to stay on the line. This will help insulate the line from the heat. If the problem goes away with the foil...it's vapor locking in the line.


i have rubber line from pump to carb


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## Sick467 (Oct 29, 2019)

Rubber line can still vapor lock, although not as likely. The foil test should still have promise.


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## Lemans guy (Oct 14, 2014)

So it sits at the light ok but stumbles on accelerating from the light.

That is often an indicator that the carb is set wrong and transfer slot which is part of the idle circuit is not coming on as you move off the light.

The idle circuit has the mixture screws and a transfer slot built into the carb barrel. When you open the throttle flap look in and you will see it. If it is mostly already under the flap it is delivers the full mixture at idle and not when it “Transitions” from stop to go with a light pedal, a very aggressive take off gives a squirt from the accelerator pump, the transfer slot is the middle between stop and the accelerator pump.

Now everything said can be considered, and this should be as well. If you suspect this, The fix is too Re move the carb turn it upside down and square the slot on the bottom, it should look square from the bottom. When you have it upside down notice how much it turns off square with just a half of a turn on the throttle screw. That should be about your max adjustment once back on.

Now reset the idle with a vac gauge and look for any change.

Vapor lock will also stall the car at idle. Vapor lock occurs in the suction side of the fuel line between the pump and the tank. The pump creates a vacumn as it pumps the fuel in the line, but vacumn lower boiling points, pressure increases boiling points.

That is why 16 lbs of pressure on your radiator raises the boiling point of the coolant, and also why fuel injection systems don’t vapor lock, because they are under high pressure which raises a boiling point.

So the feed line to the pump then turns the fuel to a vapor because of three things, the vacumn, the low volatility (Boiling point) of today’s gasoline and heat. And fuel pumps won’t pump vapor only liquid.

so you have a few things to check


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