Testing the EVAP system........

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takza
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Post by takza »

Or...fart like you mean it.......juuuuuuuuuuust kidding!

Ran thru the tests (except for the thermo switch..TVSV) for the EVAP system...includes the hoses and pipes to and from the tank, charcoal canister, OVCV, VSV.....

How it is SUPPOSED to work....as I understand it at least....

* shut the car off and the Outer Vent Control Valve opens and allows gas vapors from the carb to collect in the canister AND also the gas vapors in the tank will travel up to the canister to collect.

* start the car and the OVCV closes...and at some point the ECU opens the Vacuum Switching Valve and allows the intake to draw air thru the bottom of the canister and into the intake...drawing the gas vapors out of the canister...at some point it closes...and might even open again at times.

What was wrong.......

1) when testing the canister...all was well until I blew air into Purge Pipe B and got air out of outlet C (to OVCV)...not supposed to happen<span style='color:blue'>...could somebody verify that this test is a valid one?</span>

2) the Vacuum Switching Valve doesn't work at all...so no vapors are getting purged into the intake....

Anyone got a <span style='color:blue'>Vacuum Switching Valve </span>laying around???????

Should improve my mileage to use these gas vapors..........
Give a boy a gun-give a biatch a cell phone-and pretty soon you almost got yourself a police state.

Orwell said: War is peace! Freedom is slavery. Ignorance is strength...

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dug320
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Post by dug320 »

Hi

I am not sure what year or engine you have but ....

1985 Toyota Manual; there are only two key parts to the EVAP.

One is the cannister itself (this includes the Check Valve) and the Fuel Filler Cap (this includes a Check Valve). WD-40 the the inside of the filler cap and it should unstick the valve.

Basically, if you blow into the tank pipe air should flow out all pipes. If you blow into the purpe pipe air should NOT come out.

Replacing the cannister is the repair.
takza
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Post by takza »

Well...the VSV HAS to work or you never purge the vapors from the canister. Mine doesn't work.

The real question is that when I apply air pressure to the B (purge) I get a flow out of C...but according to the illustration there doesn't appear to be any restriction between the two...and none would be needed anyway since at all times when one is open the other would be closed.

The canister might be faulty, but the VSV is the main issue.

As far as the cap...you are saying that it should admit air if there is a vacuum in the tank...but will not allow pressure OUT up to a certain PSI level?

** Instead of chasing down <span style='color:red'>another freakin' part</span>...I'm going to try bypassing the VSV and use a slow controlled air bleed thru the canister.
Give a boy a gun-give a biatch a cell phone-and pretty soon you almost got yourself a police state.

Orwell said: War is peace! Freedom is slavery. Ignorance is strength...

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3A-C Power
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Post by 3A-C Power »

I will give you a VSV if I can find one. Was that the VSV I sent you before or was is a vacuum switch? I forget.
takza
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Location: Tibetan plateau

Post by takza »

It was the OVCV.

I set up the slow bleed thru the canister and set it so there was a slight increase in engine speed at idle. All the gas vapors from the tank and carb were pretty much stuck in the canister till now.

Might just tee into the vent line from the tank and do a slow bleed from there combined with the purge line...I'm talking a very minor flow.
Give a boy a gun-give a biatch a cell phone-and pretty soon you almost got yourself a police state.

Orwell said: War is peace! Freedom is slavery. Ignorance is strength...

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