Huntin720 Posted January 29, 2014 Report Share Posted January 29, 2014 1980 720 4x4 L20B The previous owner deleted the evap canister and plugged all the associated hoses. Including (I discovered this week) the fuel tank breather. It didn't turn up as a problem because there were leaks in both hoses on the fuel filler neck. When I replaced those hoses and closed up the system everything seemed to run well for about 30 min and then it started sputtering and eventually died. A quick look revealed no fuel in the float chamber on the carb. I removed the fuel filler cap and it came straight back to life. So I got home and took a look under the hood and sure enough there was a cap on the breather where the evap canister would have been The questions. Is it safe just to leave this uncapped in the engine compartment so that the tank can breath? (there is a valve at the tank) Shoud I track down an evap canister and restore it? If I do should I restore all the other components and hoses? Will I need to adjust the carburetor to compensate for the changes to the fuel system? What else am I missing that I should consider? Should it effect my fuel economy (either the way it was, or repairing this situation)? Quote Link to comment
Eagle_Adam Posted January 29, 2014 Report Share Posted January 29, 2014 just vent it to atmosphere, you will be fine 1 Quote Link to comment
DanielC Posted January 30, 2014 Report Share Posted January 30, 2014 Evaporative emissions control does not rob any power. It just greatly reduces the evaporation of expensive gasolline. the system basically works by holding fuel vapors whent he engine is shut off, and sending them back to the engine when it is started the next time. If the engine is cold, it needs a richer mixture then, any way. Find the factory service information on the truck. Learn how the evaporative emissions works, and hook it back up. 1 Quote Link to comment
ggzilla Posted January 30, 2014 Report Share Posted January 30, 2014 Venting the fuel tank straight to atmosphere under the hood is not recommended - gas is flammable. 1 Quote Link to comment
Huntin720 Posted January 30, 2014 Author Report Share Posted January 30, 2014 Oh I know it's not a legitimate power issue. I'm super happy to hook it back up. I just need to get an evap canister and then Im curious what the effects of the choice to remove it were? It seems like something guys do when they don't understand what it's there for. But in terms of how it interacts with the pressures in the fuel system, then I'm out of my depth. Will I need to dial in the carb to compensate for different levels of pressure available in the fuel system? Or is that the kind of thing the carb is designed to iron out on it's own? Quote Link to comment
ggzilla Posted January 30, 2014 Report Share Posted January 30, 2014 Just go to the wreckers and get a canister. Note how the lines are before you remove it. No tuning is needed. It is a vent not a restriction. 1 Quote Link to comment
Huntin720 Posted January 30, 2014 Author Report Share Posted January 30, 2014 Awesome thanks. Quote Link to comment
datzenmike Posted January 30, 2014 Report Share Posted January 30, 2014 "You always fear... what you don't know" The charcoal canister simply collects gas vapors from the carb and the gas tank and stores them while the motor is off. It reduces hydrocarbon emissions into the atmosphere. When started, the manifold vacuum opens the canister and sucks the fumes out and into the carb to be burned normally. Totally benign in operation. You can run it or not, but I would. Quote Link to comment
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