spiffiestpengui

so, i got home, and noticed when i parked, smoke coming out the sides of my hood. first thing i thought was oh great, i must have over heated. wrong. opened the hood, and the "smoke" was pouring out from under my air filter and through it. then i thought maybe it was on fire...nope. took it off and it was coming out of my carb pretty badly. even worse if i open my secondaries. it smelled like gas (obviously) so i thought well it must just be vapors...then i remembered about vapor lock. it was 106 degrees out, and i had only been driving for about 15 minutes, and i even stopped at the gas station on the way home before realizing this was going on. I read the vapor lock posts as best i could, but for some reason it looks like a bunch of coding is mixed with the text, im guessing it was supposed to be pictures there, but it made it kinda hard to read with letters and symbols all mixed in the sentances. would this have been vapor lock that im having problems with? it ran fine..just a little powerless, but usually it has been running alot worse after warming up, to the point it wants to die and not start, but those times i didnt notice the vapors coming out, and it even happens at night when its not that hot out. i dont know what to think right now. vapor lock?

//<86TA>\\

iTrader: (14)

the "steam" is the fuel boiling bad, so you will ahve vaporlock issues.

info on the fuel line routing and the engine? i assume its a carb motor? it should have a return line off the fuel pump if it is, and if its not hooked up or is clogged, this can happen.

spiffiestpengui

yeah its a stock q-jet carb on a 305 automatic 5.0. I havent looked at the fuel routing yet, so I'm not sure exactly what the setup is, but its whatever the stock 83 z28s came with. I will check for a return line and see what it has. how do i tell wich one of the 2 is the return line? does it come from the front or the back of the carb

five7kid

iTrader: (14)

"Vapor lock" is the inability of the fuel pump to suck liquid fuel from the tank due to the vaporization of the fuel in the supply line between the tank and fuel pump, primarily due to the fuel line getting hot. Since the pump is "sucking" on the line, the pressure is lowered, which lowers the boiling temperature of the gasoline.

What you are describing is fuel bowl boiling, which isn't the same thing as vapor lock. It is caused by the fuel bowl being hotter than the boiling point of gasoline at atmospheric pressure. This typically occurs when the engine coolant and the under-hood air temperatures are high, often at slow vehicle speeds (less air moving through the engine compartment), and especially if the engine is shut off when these conditions exist. This situation is why the factory offered a cooling fan that blew cooler air over the front of the carburetor while the engine was off and hot.

The cures for vapor lock are a pusher pump back by or in the tank, and a fuel return system. The pusher pump was a dealer-installed kit when customers complained of vapor lock problems. The '87 model year carb'd 3rd gens all had the pusher in-tank pump from the factory (finally).