Fuel return and vent line testing - JeepForum.com
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post #1 of 3 Old 07-18-2010, 09:06 AM Thread Starter
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1980 CJ7 
Join Date: Jul 2009
Location: NC
Posts: 256
Fuel return and vent line testing

I know I have seen this somewhere on here, but I can't find it. Right now I have an MC2100 installed and I have a rich mixture I'm trying to solve. I have installed #46 jets and now the carb floods, to the extent that the bowl overflows. This didn't happen with #48 jets, only that the engine ran so rich that I am experiencing some washing of the cylinder walls. Now to the question. My fuel return line builds slight pressure when you blow into it. I doesn't when the gas cap is off. How does the vent line back to the charcoal canister work in conjunction with the fuel return line? Should both lines "breathe" freely? I have recently replaced the power valve. Thanks.

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post #2 of 3 Old 07-18-2010, 10:30 AM
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1980 CJ5 
Join Date: Mar 2010
Location: moses lake WA
Posts: 130
check your rear drivers side fender and inspect the rollover check valve and the vapor vent can that sits there. sounds like something is plugged

1980 CJ-5, Ford 351w, in restoration, kind of
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post #3 of 3 Old 07-18-2010, 12:52 PM
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1981 CJ8 
Join Date: Apr 2010
Location: The Little Apple
Posts: 3,408
let me help you with that:

Went through the same problem. Sounds like jeffy is right - there may be an obstruction between the tank, the check valves, and the canister. My valve-canister line was plugged with charcoal when I tore down the system. That link will give you a pretty solid idea of how the whole fuel emissions/canister system is supposed to work.
walkerhoundvm is offline  

carb , cylinder walls , fuel system , gas cap , gasoline , jets , mc2100 , running rich , vent

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