What does the CPS do?

georryan · Post by **georryan** » Wed Nov 26, 2003 11:36 pm

Hey I've heard lots of talk about the Canister Purge Silanoid, but what does it do? How does it affect your car when it isn't working properly?

ciper · Post by **ciper** » Thu Nov 27, 2003 12:18 am

If it fails close it does nothing.

Fuel vapors collect in the canister, the solenoid opens to suck air through the canister taking the fumes with it. No fail safe function is associated with it in the ECU. I say replace it with a resistor!

vrg3 · Post by **vrg3** » Thu Nov 27, 2003 4:31 am

If you do that, won't the vapors collect in the canister until they spill out the overflow line, resulting in your fuel level going down all the time even if the car isn't running?

ciper · Post by **ciper** » Thu Nov 27, 2003 5:21 am

VRG3: I dont understand. The fuel vaporization rate will not change, the difference is that they will never be removed from the canister.

The valve that fails closed is from the CANISTER to ENGINE, not fuel tank to canister.

vrg3 · Post by **vrg3** » Thu Nov 27, 2003 5:29 am

Right.... I guess I don't fully understand the evaporative emissions control system.

What I was thinking was that if you never allowed the vapors to leave the canister and enter the engine, you'd end up saturating the canister. There's a little hose leaving the canister exiting to atmosphere, and I figured that once the canister was saturated the excess vapors would leave through that little hose. So, my reasoning went, if you didn't allow your engine to consume the fuel vapors you would end up losing them to the atmosphere, which would simultaneously hurt your fuel efficiency numbers and pollute the environment.

Doesn't the canister get saturated? I mean, it can't be this vapor sink forever... And if the vapors don't ever end up in your engine then they're more or less wasted, no?

ciper · Post by **ciper** » Thu Nov 27, 2003 5:33 am

Everything you said sounds right. My response is, how much fuel do you think evaporates? I dont think its much especially since most of the time your fuel tank is under vacuum! It only pressurizes when you let it sit for a while.

Besides, look at how many cars let the vapors just fly away. I think its a pollution thing rather than a fuel economy thing. Why do you think some gas nozzles have that damn spring loaded condom over them

georryan · Post by **georryan** » Thu Nov 27, 2003 8:31 am

Look what I started

Post by **Legacy777** » Thu Nov 27, 2003 5:57 pm

I hate those damn pump handles!

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What does the CPS do?

What does the CPS do?