Update on Vapor Lock and Changes made with Gas Cap/Sig difference in the 2 caps

[James Rogers]

[QUOTE=Mike V. Florida;19367]I want to take a little closer look at why a bad vent could cause vaporlock.

An unvented cap/tank won't cause "vaporlock" (wives tale). What happens with an unvented tank/cap is, when you remove fuel/liquid from a container it must be replaced by an equil amount of something else such as another liquid or solid or gas (air). In the Model A fuel system the fuel is replaced by air unless the tank/cap is unvented. In that case the fuel flowing to the carb is not replaced and causes the tank to create a vacuum which will eventually overcome the effect of gravity and starve the carb with stopping the fuel. The only way to overcome this is to add a vent to the cap/tank or open the cap. I have this problem on my cabbie and have to leave the cap loose to defeat the vent. I have tried several repo caps and all the gaskets seem to eventually rotate with removing and installing the cap at fuel time till the vent is covered. When this happens I only get a couple of miles and the car begins to starve for gas and eventually quits. If I let it sit for a while it will start and drive a couple more miles and quit again. This distance is dependent on the amount of gas in the tank, more gas less miles less gas more miles before it quits.

I still don't believe in vaporlock in a gravity fuel system.

[Bob A.]

"I still don't believe in vapor lock in a gravity fuel system".

James I agree 100% with you.
Vapor lock is caused in cars with an external fuel pump where as the suction side /line to the pump may be too close to an exhaust pipe or other heat source. This is one reason why modern cars that are capable of running at high temperatures have their pumps placed in the tank where there will be no external suction line and run nice and cool.

[Mike V. Florida]

Originally Posted by James Rogers

An unvented cap/tank won't cause "vaporlock" (wives tale). What happens with an unvented tank/cap is, when you remove fuel/liquid from a container it must be replaced by an equil amount of something else such as another liquid or solid or gas (air).

I never said it was an unvented tank/cap!!

I said "I want to take a little closer look at why a bad vent could cause vaporlock. ... If you have a bad vent in the cap (missing or clogged) and if the gasket is old and not sealing properly".

[James Rogers]

Originally Posted by Mike V. Florida

I never said it was an unvented tank/cap!!

I said "I want to take a little closer look at why a bad vent could cause vaporlock. ... If you have a bad vent in the cap (missing or clogged) and if the gasket is old and not sealing properly".

The only place the tank gets vented is in the cap. I still stand by my post that a bad vent no matter where it is won't cause vaporlock. 2 different things vaporlock and a bad vent.

[msmaron]

Originally Posted by James Rogers

The only place the tank gets vented is in the cap. I still stand by my post that a bad vent no matter where it is won't cause vaporlock. 2 different things vaporlock and a bad vent.

OK lets remove the word Vapor Lock.., dont you agree that with a bad or NON vented cap you can have the car shut down because the gas wont flow in gravity system?
mark

[James Rogers]

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Originally Posted by msmaron

OK lets remove the word Vapor Lock.., dont you agree that with a bad or NON vented cap you can have the car shut down because the gas wont flow in gravity system?
mark

Exactly the point I was trying to make. I do believe, your problem is because of dirty fuel system.