Fuel vapor in carbs

All Models and Years
Post Reply
User avatar
66corsaguy
Posts: 167
Joined: Sat Apr 01, 2017 10:34 pm

Fuel vapor in carbs

Unread post by 66corsaguy » Mon Jan 22, 2018 8:58 am

Is it normal to have fuel vapor in the carb? I don’t have the filters installed on my carbs. When i shut the car off i open the throttle plate and see vapor waft out

I also see vapor exit the exhaust. Not a lot. It’s white so I’m guessing it’s fuel?





Sent from my iPhone using Corvair Forum mobile app

66vairguy
Posts: 1485
Joined: Tue Dec 21, 2010 3:44 pm

Re: Fuel vapor in carbs

Unread post by 66vairguy » Mon Jan 22, 2018 9:59 am

When the engine is off and you open the throttles on a HOT engine the carb accelerator pumps squirt in fuel and that turns to vapor. Normal

If the carburetor clusters are "dribbling" fuel at idle then the floats need to be adjusted to lower the fuel level, AND check fuel pressure if you have a mechanical fuel pump.

The lead free fuels are more volatile and evaporate easily (not the fault of added alcohol). Very common to go out to a car after a few days and the carburetors are DRY. One reason for the installation of electric fuel pumps on Corvairs.

White smoke in exhaust is usually water vapor, or if you have an automatic transmission the modulator valve can leak transmission fluid into the engine vacuum balance tube and it does burn white.

Excess fuel usually produces black smoke. Oil is either black or blue colored.

User avatar
66corsaguy
Posts: 167
Joined: Sat Apr 01, 2017 10:34 pm

Re: Fuel vapor in carbs

Unread post by 66corsaguy » Tue Jan 23, 2018 5:19 pm

66vairguy wrote:When the engine is off and you open the throttles on a HOT engine the carb accelerator pumps squirt in fuel and that turns to vapor. Normal

If the carburetor clusters are "dribbling" fuel at idle then the floats need to be adjusted to lower the fuel level, AND check fuel pressure if you have a mechanical fuel pump.

The lead free fuels are more volatile and evaporate easily (not the fault of added alcohol). Very common to go out to a car after a few days and the carburetors are DRY. One reason for the installation of electric fuel pumps on Corvairs.

White smoke in exhaust is usually water vapor, or if you have an automatic transmission the modulator valve can leak transmission fluid into the engine vacuum balance tube and it does burn white.

Excess fuel usually produces black smoke. Oil is either black or blue colored.

Ok!! That all sounds good good good. Than everything is looking to be normal!! It’s a 4 speed so i will assume it’s water vapor. It acts a little different than water vapor as it’s sort of a thicker waft (like what i see in the carb) so i thought maybe its fuel....

I have an electric fuel pump but i only use for a few seconds to prime the carbs. I like my manual pump although i have gone thru two that fuel was shooting out like a finger on a hose. So many stories about the pumps but i think i got a good one from Clark’s as it’s not given me problems in a year (knock on wood)

I use to have a dribble and adjusted carbs based on terribleteds measurements and it fixed it. Although i should check the pressure just cos....

Thanks!!!


Sent from my iPhone using Corvair Forum mobile app

Post Reply

Return to “Ask your Mechanical Questions here”