When take off my gas cap, there is quite a noticable amount of pressure that hisses out. This seems to have increased lately, and I seem to be having a lack of power around 6500 - 7000 rpms. I have removed my rats nest also. Anyone who has any idea what could cause this please lend a hand. I've searched but don't exactly know what a check valve is, or if it is still used the same way once there is no rats nest. Thanks.

 

The pressure in the tank is released through the "check & cut" valve then leads to the charcoal cannister for "cleansing of the vapors" before being vented to the atmosphere. If any part of this system gets clogged, you will have issues. Sometimes, when someone has recently removed the rat's nest and report this problem, there will be large amounts of gasoline in the cannister which blocks the flow of the vapors. Can't remember for sure what causes this though...

 

I solved this issue on my car (83 GS) by simply drilling thru the restrictor located in the inlet of the charcoal canister. The small hose is the fuel tank vent, and there is restrictor in the nipple, with a very tiny hole in it. This can plug up very easily. Took under 5 minutes from start to finish, and no more pressure buildup in the fuel tank.

 

happened to mine after i did my carb rebuild ... it was from an improper connection to a vacumm line that somehow blocked off gasses f rom exiting there for creating pressure in the tank.

 

i am in the process of removing ALL my emissions on my 85 gsl. i just pulled that canister out, and was going to plug the rubber line, but maybe that is not a good idea?

should i just route the lines together? or what should i do? i really don't want that charcoal canister in there if i don't need it.

nick

 

ya best way is to probably connect it without the with a long hose from the carb to the line ...

 

The thing is that the rats nest is indeed for emissions, however most people don't know that the rats nest has connections that advance your timing at higher rpm's. If you notice - there are two hoses hooked up to your distributer which then go into to your rats nest.

 

The charcoal canister serves 2 functions.
First, it is the fuel tank vent.
Second, it is the crankcase (or whatever else you wanna call it) vent.
Do not plug either hose that hooks to the CC, or you will have problems. Plugging the tank vent hose will cause vacuum/pressure issues in the tank. Flooding and/or starving for fuel will follow.
Plugging the engine vent will cause pressure to build up inside the engine, and lead to oil seals leaking no matter how often you change them.
Connecting the hoses together really isn't a good idea either. I don't know about anyone else, but I certainly do NOT want my fuel tank to vent into the engine..........
I see many threads about the canister "plugging up", but I bet most times it is simply the small orifice inside the smaller (fuel tank vent) hose fitting. You oughta look at just how tiny that hole really is.
My advice, either drill out the orifice and leave the canister, or just leave the hoses unplugged, allowing more moisture and dust into the fuel tank and engine oil.

 

Well, if you follow the directions correctly, then those two vacuum lines get reconnected. Removal of the rat's nest does not affect ignition timing.

 

I pulled off a small line going to the charcoal canaster and it seemed to have worked. So it must be the charcoal canaster which is plugged up, right? This is a new thing, I removed the rats nest about 1 year ago.

 

I would bet it's the same orifice inside the small nipple of the charcoal canister that I was reffering to, that is actually plugged up. The CC just slides down into the mount, so try pulling the other hose, and lift the CC off. Look into the small nipple, and you will see the restrictor. I bet it looks like mine did, all corroded up. There was once a very tiny hole. I used a 1/8" drill bit, which was far bigger than needed. I couldn't get my torch tip cleaner to go thru, so I just drilled it out. Solved the problem instantly.