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Discussion Starter · #1 ·
Hey guys just wondering what causes it? I find sometimes when i go to fill up my tank there sure is a lot of pressure in there. Thanks. ;D
 

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Basically vapor lock is when the fuel gets hot enough to create vapor. That vapor gets caught in the fuel line and won't allow fuel to get to the carburator. A fuel system with a fuel return will help reduce this, but not necessarily eliminate it. Having a fuel pump back at the tank can also help, as can adding a fuel cooler.
Fuel injected vehicles don't normally have this problem due to the design, an electric fuel pump in the tank, higher pressure (14psi), and a fuel return system.
 

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Is it pressure or suction? Mine sucked like there was no tomorrow when I took the cap off. I finally disconnected the line to the cannister to solve mine.








EZ
 

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pressure in the tank isn't what I call vapor lock. But mabey it needs better venting.

The vapor lock I'm used to is when the vaporized fuel (from heat) just doesn't burn good since there's not enough fuel in the mix and the vehicle starts bucking and stalling out. Used to add a little diesel to the tank on an old gas Massey tractor to help that problem.
 

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Vapor lock is exactly that, the fuels hot, and you're air fuel density is jacked so bad that the vehicle bucks and sputters cuz there isn't enough fuel. I've experienced problems with that but only on the HOTTEST of summer days. Since I've put in my electric holley fuel pump no problems at all.

My most common problem I had was the sucking sound when you go to fill up the tank. I solved this by disconnected my vent line from the charcole canister, and leaving the vent line free breathing. It is my hypothesis that when you get that vacuum, it prevents fuel from pumping freely to the carb. I'm unsure of what the pressure is on a mechanical fuel pump, but hey... anythings possible in a vacuum! Didn't you guys ever see that movie, Backdraft?
=)
Chief
 

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since i have no etra on my truck like charcol canister is what i do is plug the vent line then i go to my gas cap and take off the rubber o-ring so that it can vent their or i leave the cap loose
 

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mopar-man 3000 said:
since i have no etra on my truck like charcol canister is what i do is plug the vent line then i go to my gas cap and take off the rubber o-ring so that it can vent their or i leave the cap loose
In Texas, they check your gas cap on inspection. So it has to work properly. The vented gas cap always passed inspect, but the vent line would pull too much vacuum and the cap couldn't keep up. Never have been able to get an answer as to why it does, so I just unhooked it....

EZ
 

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If you're having a problem with vapor lock, try changing your fuel filters. The one in the carburator of my truck wasnt changed for the first 8 years of it's ownership, and it caused a problem that all the experts diagnosed as vaporlock. it went away completely, and we couldn't blow air through the old filter...
 

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Discussion Starter · #9 ·
Thanks for the input guys, guess ill be checking on a few things this weekend. Dave ;D
 
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