Vacuum

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Steve123

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Good Morning all. I have a 1986 1/2 ton, with a 350. I am putting in a new engine. I have the motor out and thought it would be a good time to clean up the engine compartment. I media blasted the engine compartment and painted it. I wanted to eliminate as much of the unnecessary emissions as possible. Can I remove the Canister? and the Air Tank? The truck has heat, A/C and dual gas tanks. Thanks
 

Charlie

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Yeah, welcome to the forum Steve.
 

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[QUOTE="Steve123, post: 417045, member: 15466] Can I remove the Canister? and the Air Tank? The truck has heat, A/C and dual gas tanks. Thanks[/QUOTE]
If by air tank you mean the round black thing about the size of a softball, I think you need that if you have a/c. Someone else will here know for sure.
 

HotRodPC

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I wouldn't remove the canister. It's really not in the way anyway is it? Your fuel tank is going to be ventilated and if dual tanks then all those lines are necessary. If you start removing them then you're losing ventilation to the tank and/or having leaks at the valve etc. I'm not sure what air tank you're talking about unless you have a vacuum resevoir and that's needed to operate you air handler box for the heat, defrost and AC. If the vac diaphrams don't have enough vacuum, they won't function to move your blend doors and you should have 3 of those. One for Hot and Cold, one for Floor to Bi-level, and one for defrost.
 

Steve123

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I wouldn't remove the canister. It's really not in the way anyway is it? Your fuel tank is going to be ventilated and if dual tanks then all those lines are necessary. If you start removing them then you're losing ventilation to the tank and/or having leaks at the valve etc. I'm not sure what air tank you're talking about unless you have a vacuum resevoir and that's needed to operate you air handler box for the heat, defrost and AC. If the vac diaphrams don't have enough vacuum, they won't function to move your blend doors and you should have 3 of those. One for Hot and Cold, one for Floor to Bi-level, and one for defrost.

It's really not in the way anyway is it? No it is not in the way. I took pretty much everything out of the engine compartment, except the master cylinder/booster, steering and wiring. Took out the front clip and both inside fenders. Wanting to clean it up and didn't want to put it back in if it wasn't necessary. I'm not sure what air tank you're talking about unless you have a vacuum reservoir Yes I was referring to the vacuum reservoir. Thanks for the info, I will put it back in.
 
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HotRodPC

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WHOA ****, black text on a black background just don't work. I'll edit that.

Welcome to GMSB Steve. Hit the QUOTE button, then type your response and you won't have to color the text. Much simpler and easily legible. :waytogo: I've edited your post above so you see what it would look like.
 
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1987 GMC Jimmy

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Both of those guys are right depending on what you’re talking about. I wouldn’t get rid of the charcoal canister, and if you’re also talking about the vacuum storage reservoir, you need that for HVAC control and cruise control if you have it.
 

maxtwms

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Mine looks like this right now but I would also like to know how I should set up my charcoal canister... anyone got any clue where each hose goes? Ive labeled the can ports 1-4.. Yellow are my current vacuum lines.
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bucket

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I removed the charcoal canister on my '84. The tank vent line just got left open in the engine compartment. Until I dropped the tank, then I just capped the nipple with a vent, much like a diff vent. It could have been capped completely, as long as a vented fuel cap is used.

My only vacuum lines now are for the pcv and dizzy advance. The trans modulator and HVAC share a vacuum source at the rear of the manifold.
 

chengny

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Welcome from South Dakota.

[QUOTE="Steve123, post: 417045, member: 15466] Can I remove the Canister? and the Air Tank? The truck has heat, A/C and dual gas tanks. Thanks
If by air tank you mean the round black thing about the size of a softball, I think you need that if you have a/c. Someone else will here know for sure.[/QUOTE]


Since its a dual fuel tank setup; when he says "air tank", maybe he's talking about the auxiliary EE canister. Only used with dual tanks. It is piggybacked onto the main one to accommodate for the additional vapor generated by the second fuel tank. It only has one hose (into the bottom), so it does kind of look like a little air tank:



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The auxiliary canister (ACC), Fig. 60, is added to some systems with enlarged fuel capacity (dual or optional fuel tanks) to increase the vapor storage capacity of the EEC system. The auxiliary canister is used in conjunction with a closed bottom main canister and connected to the main canister purge air inlet. The auxiliary canister stores vapor overflow from the main canister, and during purging, air is drawn into the system through the auxiliary canister vent.
 

chengny

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Mine looks like this right now but I would also like to know how I should set up my charcoal canister... anyone got any clue where each hose goes? Ive labeled the can ports 1-4.. Yellow are my current vacuum lines.
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The way the hoses are identified should give you a pretty good idea where they should be connected. But be advised that due to the fact that you have eliminated the "EGR/PURGE TVS", the EE system will not function as well as designed. If port 2 is properly connected to the fuel tank, when the engine is off the canister will adsorb any hydrocarbon vapor that flows into it. Same goes for port 3 - if it is connected to the carburetor bowl vent. But without the vacuum signal - from the TVS - which is required to pull the purge valve open, some of those vapors never get drawn into the combustion air stream. They (the vapors) will just stay there. Eventually canister's carbon bed will become saturated and won't adsorb any more vapor - after that any more incoming vapor will just spill out to the atmosphere.

Here is a good drawing (view is from forward looking back) and explanation of how GM's purge type canister works:

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1984-87 Engines
This system Fig. 63, absorbs and stores fuel vapor in a carbon element until it can be removed and burned during normal combustion process. The canister is equipped with a vapor bowl vent control valve and a canister purge control valve which are both mounted on the canister.
The bowl vent control valve operates as follows:
  1. When the engine is off, there is no vacuum through the vacuum signal tube to the valve diaphragm, spring tension opens the valve. Fuel vapors formed in the carburetor float bowl are pressurized to the point where they flow from a tube in the carburetor float bowl through a connecting hose marked ``Carb Bowl'' in the canister cover. Vapors travel past the open vent valve through the filter in the canister onto the activated charcoal, where they are stored until purging of the canister occurs. When the engine is running, vacuum is supplied through a tube marked ``Man Vac'' to the vent valve diaphragm. The diaphragm moves upward, raising the vent valve upward, against spring tension, allowing the valve to seal the passage venting fuel vapors from carburetor float bowl to canister. When engine is stopped, spring tension opens the valve to allow venting of the carburetor float bowl.
The canister purge control valve operates as follows:

  1. Fuel vapor is inducted into the engine and is controlled by an orifice in the purge control valve. Ported vacuum signals to the purge control valve is controlled by a thermal vacuum switch (TVS) which delays purging until a specified engine temperature is reached. With throttle closed, the purge control valve diaphragm is seated by spring tension and no purging occurs. With throttle opened, ported vacuum is applied to the purge control valve. With vacuum applied to the diaphragm, the valve is opened when ported vacuum develops sufficient force to overcome preload of the diaphragm closing spring and purging takes place until the throttle is closed to a position which reduces ported vacuum to a level at which it can no longer overcome diaphragm spring tension.
 

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Pix please.
 

Steve123

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Thank you everyone for the info. I am going to leave the canister and vacuum reservoir in place. It appears that the only thing connected to the canister was the vapor from the fuel tank.

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