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Unread 08-25-2015, 06:40 PM   #1
jhrebs
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1987 YJ Wrangler 
 
Join Date: Jan 2012
Location: East Windsor, NJ
Posts: 481
I am replacing some of my old dry rotted vacuum lines. A couple of quick questions. There is a small vacuum line that runs off the canister near the battery all the way to the driver side and then down. It then connects to what looks like a metal tube that goes to the rear. At the canister there was a very small plastic fitting inside the vacuum line with a pin hole almost looking like to restrict air. Does that need to be there!?!? Mine went missing! Also for the life of me I could not get the same size tube on it. Should that be a big deal that I went a bit larger? And final, what is this vacuum line for?

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Unread 08-25-2015, 07:03 PM   #2
Rudys88
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1988 YJ Wrangler 
 
Join Date: Feb 2014
Location: Bartonville, Texas
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The canister provides reserve for the pulse vacuum system, carb solenoid and on my 88, it supplies vac to the 4x4 engagement as well. Having the reserve keeps the vacuum supply constant to these parts while the manifold varies with engine operation. Otherwise under load, these solenoids could not operate correctly. My canister has a check valve on it to prevent stored vacuum from leaking back to the manifold when the engine is loaded. I don't have restrictor as you mentioned on my system. Go to this valuable source of info, Dale Beckett's site to see an excellent illustration. An invaluable site that has helped me with my 88 wrangler restoration. http://home.sprynet.com/~dale02/vacuhose.htm

Good Luck.
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Unread 08-26-2015, 12:21 AM   #3
kgbeast
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The line that op describes is the fuel tank vent. It needs to be connected fron the canister to the fuel tank. Whomever owned the jeep before probably added this restrictor for some kind of snake oil fix.

I have 89 4.2 carbed sahara and my canister is located on the driver side under the windshield washer fluid bottle. The vapor canisters for jeep or any other car is a plastic container filled with charcoal and is basicaly a filter to absorb the gasoline smell from fuel tank and the carb bowl. It is not to store any vacuum as it has no vacuum tank in it and actually has no sealed bottom. It actually has a mesh and a spunge filter at the bottom to contain the charcoal.

"4x4 engagement" the previous poster talks about is actually the front axel locker (locked dif). It is locked using a vacuum switch when in 4L mode only. It uses manifold vacuum to do that and the canister has nothing to do with that... Nor it has anything to do with any of the solenoids. Vapor can is strictly a polution control item.

There are four lines are attached to the canuster. Fuel tank (thinner line comes from a metal tube comes from under the driver side). A fat tube that goes to carb and splits to the bowl cover and top of the bowl. This tuve is probably 5/16 id. Another tube about 1/4 " id goed to the manifold vacuum under the carb (this line is called the purge line). And a vacuum signal, thin line that goes to the cto switch located just forward the carb [below the idle mix screws].

Vapors from carb bowl and fuel tank find their way to the canister and stay trapped in it untill the engine is at normal op temp and rpms are somewhere above around 1500 rpm. The cto would be opened and the cto vacuum is high enough to open the valve at the top of the canister (the vacuum signal). This valve connects the purge line to the contents of the vapor canisters, the trapped vapors, to be sucked out of the canister nto the manifold.

During idle, even though the cto is opened, there is not enough vacuum to signal the canister valve open and this ensures that the purge process is not active and all manifold vacuum is sealed to ensure proper idling. If the vacuum at the top of the canister does not hold vacuum, it is because the diaphragm has a tear in it which connects the vacuum signal line and the purge line to the contents of the canister and is venting out enough of the manifold vacuum to make the engine incapable of proper idle. Often the engine idles highish and rough even with the idle screw completely out. In that case it is probably best to plug the purge line altogether... However without the can purge, there will be a smell of gasoline around the vehicle. Repairing the membrane is pain in the a$$ and usually is not productive. Finding replacement canister is close to impossible. It is however pretty easy to locate a chevy vapor canister. It is basicaly the same function, but larger and has an extra valve that can be simply left not used. It also is intended to be connected to the cars air filter housing as it has no its own spunge filter like the jeeps canister. All'n'all retrofitting chevy canuster is pretty easy.

So check your canister that it operates properly. To do that simply suck on purge port of the canister. It should be closed tight. If you suck also on the vacuum signal port, it should hold vacuum and under the vacuum condition, it should open the purge port. The carb bowl and fuel tank bowls are always open on jeeps.

Another thing to check after you replace all vac lines is the EGR valve operation and air injection system.

EGR is connected to the same cto switch, but EGR valve does not hold vacuum and need to be somewhere above 1500rpm to start moving. You can look at the EGR valve stem through the one of the 4 opening and rev up the warmed up engine to above 1500 rpm... You should see pretty obvious movement of the EGR valve stem. If it does not move, rev up some more, if stll nothing, checkvthat there is vacuum in its hose.

To check air injection, remive air filter and you will see two huge holes in the bottom of the air filter housing. If you quicly depress the throtle to quickly rev up the engine so the carb spews out two streams of gasoline, the air injection system should start running and if you try to plug the two holes in the air filter housing, you should feel pretty good, pulsating sucktion in both holes once the engine returns to idle. The sucktion should stop after a couple of minutes of engine idling.
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Unread 08-26-2015, 05:22 AM   #4
Mike Romain
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Which canister are you talking about? The one under the battery is normally a vacuum reservoir for the 4x4 switch and heat controls. The one over on the drivers side is the gas tank vent.
The vacuum reservoir does need the restrictor.
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 08-26-2015, 09:31 AM   #5
jhrebs
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1987 YJ Wrangler 
 
Join Date: Jan 2012
Location: East Windsor, NJ
Posts: 481
I am talking about the canister under the battery tray. There is a small vacuum line that goes to the rear of the jeep via a metal tube. the restrictor was in the hose
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Unread 08-26-2015, 09:58 AM   #6
kgbeast
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In this case there is a vacuum line to the transfer case, although, I thought it was rubber hose not metal tube. When you said "canister" all I could think was the vapor canister. That said, there is no restrictions that are needed regardless of which "canister" you are talking about. The fact that someone went through an effort to put it in, probably done so because something is not working. You will need to test all that as well and see what is out of whack.
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Unread 08-26-2015, 10:36 AM   #7
jhrebs
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1987 YJ Wrangler 
 
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Well I did trace this to the fuel tank. It is in fact rubber then connects to the metal tube(almost the size of brake line) and continues onto the fuel tank. So that make me think this canister is the vapor canister. I also did find this restrictor so I just put it back in. My mechanic at my shop(non vehicle) thinks it might be to restrict suction so as to not suck up actual fuel?
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Unread 08-26-2015, 10:36 AM   #8
Mike Romain
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Quote:
Originally Posted by kgbeast View Post
In this case there is a vacuum line to the transfer case, although, I thought it was rubber hose not metal tube. When you said "canister" all I could think was the vapor canister. That said, there is no restrictions that are needed regardless of which "canister" you are talking about. The fact that someone went through an effort to put it in, probably done so because something is not working. You will need to test all that as well and see what is out of whack.
The ones I have seen had the restrictor in the line. That stops vacuum surges from affecting things badly.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 08-27-2015, 07:13 AM   #9
kgbeast
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Quote:
Originally Posted by jhrebs View Post
Well I did trace this to the fuel tank. It is in fact rubber then connects to the metal tube(almost the size of brake line) and continues onto the fuel tank. So that make me think this canister is the vapor canister. I also did find this restrictor so I just put it back in. My mechanic at my shop(non vehicle) thinks it might be to restrict suction so as to not suck up actual fuel?
I remember now... A few days back i saw your thread about starter relay wiring and in the pictures, i could see the vapor can under the starter relay, on the passenger side. This is an unusual place for the can as usually i see those on the other side. I think this is the confusion. That canister is a stock can from what i see. It is not a vsc reservoir.
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