my evap system had pinholes.i disconnected it&got mpg's

fixityourselfer · Post by **fixityourselfer** » 03 Jun 2009, 20:48

hey guys, my mileage was real bad cuz my evap system was full of pinholes so i disconnected the vac hose between the evap valve (right under the intercooler-TB hose) and the Tee that goes to the inlet manifold.

I plugged the Tee. i left the open evap alone. no code. mileage has gone back to where it belongs.(cheers)

can i continue to drive like this? any reason i really need the damn evap anyway??!!

Post by **Ozark Lee** » 03 Jun 2009, 21:48

any reason i really need the damn evap anyway??!!

I suppose it depends on your political persuasion and whether or not you believe in global warming, carbon credits, etc.

The EVAP does help the car start in the morning since it purges the gas fumes into the intake manifold on startup. Beyond that it is just expensive greenie stuff up to the point where gasoline leaks out when you fill the tank.

...Lee

Post by **Brucebo** » 03 Jun 2009, 22:05

What year is your car? If it's OBDII eventually the EPA EVAP monitor I/M test will be run setting a code. You can reset these but some states allow no more than one or two I/M monitor tests to be in a pending state (and none failed).

-B

Post by **vegasjetskier** » 03 Jun 2009, 22:09

So if it's disconnected is the system venting gas fumes into the engine compartment? Might not be too safe . . .

fixityourselfer · Post by **fixityourselfer** » 04 Jun 2009, 13:49

i don't think it will vent fumes to engine compartment cuz it can only vent if there's vaccum. now there's none. correct?

newowner · Post by **newowner** » 21 Nov 2010, 19:44

Follow-up: How well this work. What year is your car & did your check engine come back on ???
I've been working on mine from early spring, I've changed "J" hose, the hose right next to the "J" and resealed the Evap valve. The light keeps coming back on....
So I'm thinking about trying this method.

Post by **Jack Rock** » 21 Nov 2010, 20:47

I'm also curious about the results of this method. My 97 850 comes up with a 422 code which I know is a catalytic converter efficiency code but it only comes up when I fill the tank. I ran for two months only putting 25 litres in the gas tank and never had the code once, but the first time I filled it up the CEL came on within 100km. So I suspect the EVAP first and was wondering about trying it disconnected but am concerned about vapours in the engine compartment. Would I disconnect the vacuum line on the manifold side of the purge valve and cap the tree? What about pinching off the line from the EVAP?

VolvoTurbo850 · Post by **VolvoTurbo850** » 21 Nov 2010, 21:49

I think it is about being green more than you turning a shade of green from the vapours. Any classic car owners who never had that system on their autos may tell you the vapours smell bad but I have not heard of too many blowing up.

I just know in the long run, these Volvo's will act up if you do not have them running efficiently.

Free2drive! · Post by **Free2drive!** » 22 Nov 2010, 03:20

Yes your mpg will be better because you have dealt with the vacuum leak. Gas tanks used to vent to atmospher so your fuel was evaporating away. On volvos the vapour is caught in a carbon filled canister. On start up the gas vapour is drawn into the motor via the evap valve and burnt.

Replace your carbon canister and your car will run even better.
Matt

Btw what happens in the US to the carbon canister when the car us crushed?

Post by **thecheat** » 22 Nov 2010, 08:54

The system is to keep gas evaporating from the fuel tank from getting into the atmosphere. The charcoal canister is to trap the evaporated fumes when the car is off. When you turn on your car the evap purge valve sucks in the trapped fumes and then closes after an amount of time. If this valve is bad you will get a code because it will be a large vacuum leak and of course you will get bad mileage as well since it affects the fuel mix. I have a writeup here about testing and repairing the valve - it's pretty easy to do.

You can just close the vacuum hose going to the charcoal canister but then your fuel tank is evaporating to the atmosphere which isn't great for the environment... supposedly these fumes are a significant air pollutant.