NEED HELP with fuel EVAP system.

General technical discussion and troubleshooting
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bobabob
I am merely driving my van
I am merely driving my van
Posts: 1
Joined: Thu Oct 08, 2015 11:01 am

NEED HELP with fuel EVAP system.

Post by bobabob »

my van failed smog due to the new evap test laws. and for people outside of CA who dont know what the evap test is. its a test of the fuel evaporative system and components. they pinch the evap lines closed at the evap canister (mine happens to be under the hood, but i think most are ontop of the tank.) and they pressurize the system with inert gas using a fuel cap with a hose fitting on it.

ok so i failed the initial smog test so i cut an access to the fuel pump and replaced the gasket under the fuel pump. retested it and failed.
http://postimg.org/image/g6ugxmaiz/

so then i decided to eliminate the evap lines from the test before replacing all of them. so i disconnected the two dry lines coming out of the fuel pump and replace them with short line leads with caps on them. i had it retested and failed again.
http://postimg.org/image/3w1j1mvij/

so my question is, i dont know much about the layout of lines coming out of the tank of these vans but i would imagine my leak has to be in the fuel tank filler neck right? is there any other places i may have missed?

1995 chevy astro rwd 4.3L

Karen
I am merely driving my van
I am merely driving my van
Posts: 2
Joined: Thu Jul 30, 2015 7:35 am

Re: NEED HELP with fuel EVAP system.

Post by Karen »

The evap canister was originally designed to take excess fumes from the engine hence first two letters of the word exhaust vapor. So there should be a line coming off the egr (exhaust gas recirculation) valve or the egr solenoid which signals the egr to open to the evap canister and a line from the canister that goes to the carburetor to burn off the excess vapor.Occasionally those lines which go into the carb(TBI) get mucked up. You should be able to see them from under the hood pull them off one at a time and see if it is plugged there and check the hoses to make sure they aren't plugged. Good luck.

AstroWill
I finally get the smurf thing
Posts: 163
Joined: Sun Nov 14, 2010 12:09 pm

Re: NEED HELP with fuel EVAP system.

Post by AstroWill »

What what what? Ok, please ignore the posting by Karen as it is super duper just plain wrong.
Karen wrote:The evap canister was originally designed to take excess fumes from the engine hence first two letters of the word exhaust vapor.
The EVAP system has ZERO to do with any fumes from the engine
Karen wrote:So there should be a line coming off the egr (exhaust gas recirculation) valve or the egr solenoid which signals the egr to open to the evap canister and a line from the canister that goes to the carburetor to burn off the excess vapor.
The EGR and EVAP system have nothing to do with each other, and these vehicles don't have a carburetor.
Karen wrote:Occasionally those lines which go into the carb(TBI) get mucked up. You should be able to see them from under the hood pull them off one at a time and see if it is plugged there and check the hoses to make sure they aren't plugged. Good luck.
Not likely to be plugged in the EVAP system, though on an EGR system you can get carbon build up.


The EVAP system takes fuel vapor from the gas tank and they get absorbed by the EVAP canister(contains activated charcoal), then under the correct conditions, it opens the valve to allow those vapors to be sucked into the engine be burned off instead of being released directly into the atmosphere.


To answer the OP, if you have capped off the lines from the tank, and you still have a leak, yes I would be looking towards the filler/neck. A fuel line/return leak would show up as well. The best way to find these leaks is to use a smoke testing machine, or simply replace the lines ;)
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