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Vacuum Line Question / Layout

Muad'Dib

Muad'Dib

NAXJA Forum User
Location
Bend, Oregon
Last year when i didnt have time to work on my Jeep ('90 RENIX) i took it to the dealership to fix a high idle. They said it was vacuum lines, fixed it, and i was on my way. Lately i have been having an "low" idle problem when the engine is cold. As part of my diagnostics, i have been trying to find / check / replace all the vacuum lines that are disconnected (some are very hard to find) etc.
Well last night i was doing this and i found two on the passengers side that were not connected to anything. I dont know what these would go to, or maybe they go together. So i figured i would post here.
One of them is blue, and i believe (i could be wrong) that it is part of the 4wd vacuum system. Its located directly below the coolant bootle on the firewall. Here are some pictures:

Pulled up to show the bottom:
http://i13.tinypic.com/628bvdc.jpg

Laying down: You can barely see its "UFO" head:
http://i11.tinypic.com/4q7qvcg.jpg

Shown with a magnetic pic up. The head of the magnet is where i found it sitting between a yellow and red (I think) vacuum lines:
http://i16.tinypic.com/61yweo9.jpg

Now here is the other one. Its just a plain black one that i believe runs to that round canister that sits behind the passengers side front bumper.

Pulled out to show it a little better:
http://i13.tinypic.com/503y25c.jpg
http://i9.tinypic.com/4uvemj4.jpg

Part of where it is ran. Big picture, but i wanted to give you the idea of where it is ran. Its to the left of the relay. Its got a zip tie around it and something else: Im pretty sure it runs to that round canister behind the bumper. But im not 100% certain.
http://i9.tinypic.com/6h3gubm.jpg


I hope these pictures help. I just would like to know where these are supposed to be plugged into. Maybe im thinking too hard and they just go together, but i want to be sure.


Oh and just in case you want to know what all that wiring is for:

http://i13.tinypic.com/630v4fk.jpg

Thanks guys for all your help!!
 
Heres the vacuum line routing for a Renix era jeep

Hope it helps

86744v06L.gif

86744g49L.gif
 
The head on that last one definitely looks like the one that tees into the line that runs to the canister behind the front bumper. On that blue one, I think the UFO head might just be that, I think when I had a CAD, mine was the same way.
 
The "UFO Head" should be a vacuum check valve.

The lines on the passenger side of the engine are for accessory control (HVAC, disco axle,) rather than for engine management. A vacuum leak there would still cause a problem - but you can just track them down and cap them off at the source to isolate the systems.
 
RenixPower said:
The head on that last one definitely looks like the one that tees into the line that runs to the canister behind the front bumper. On that blue one, I think the UFO head might just be that, I think when I had a CAD, mine was the same way.
Click to expand...

"Tees into the line that runs to the canister"

Where is the tee located? Could you possibly snap a picture for me for clarity?
I take it then the blue line with the UFO head doesnt go anywhere it just sits there?

5-90 said:
The "UFO Head" should be a vacuum check valve.
Click to expand...

Is what i said above true? Since its a check valve, it just sits there with no other connection?
 
Ok for an update, i still dont know where that darn blue vacuum line (With the UFO Check valve) goes, or if it just sits there minding its own business.

What i do know know is where the rest of the vacuum lines go on this side. Or at least i know for my '90 RENIX. Turns out that Jeep, or who ever owned it before me bypassed the stock vacuum lines and ran thier own. Only to leave the cracked stock peices behind. I pulled them out here they are:

http://i12.tinypic.com/61vdvfn.jpg

I will try to be as detailed as possible. to help others who find this thread.
I DO NOT have cruise control, but i do have the vacuum controlled front axle and air conditioning. I have the "Round" vacuum canister, not the "football" or "pill" shaped ones like some others do. There are only two vacuum connections on mine. One is bigger then the other.

Both of them go from the canister behind the front bumper and run up and along the passengers side of the Engine. Here is a picture of one, you can see it stuffed down there with everything else :p
http://i15.tinypic.com/4xxicqs.jpg

Now the smaller of the two runs into the firewall. There is two vacuum lines coming out of the firewall directly above the spot where the A/C lines connect at the firewall. The one that is black on the left is one the runs to the smaller hole on the vacuum canister.
Here is a couple pics:
http://i13.tinypic.com/4pdj5za.jpg
As seen at the firewall at the end of my magnetic pic up:
http://i10.tinypic.com/5zlfnlt.jpg
http://i12.tinypic.com/4qg7thc.jpg

Now the other hole (larger one) from the vacuum canister runs all the way around the firewall to the drivers side of the engine, to come to rest on the intake manifold. Here are a few pictures:
http://i11.tinypic.com/6cesqok.jpg
http://i16.tinypic.com/4pwwh3p.jpg
http://i15.tinypic.com/4ktjp1u.jpg
http://i12.tinypic.com/52wp08o.jpg

I hear some people talk about a "Tee" Here is what mine looks like:
http://i12.tinypic.com/6ajyger.jpg
http://i12.tinypic.com/4xniquh.jpg
http://i10.tinypic.com/67oefbc.jpg

A vacuum line runs from some type of sensor??? maybe?? that also has a ground that would be worth cleaning up like the rest of the grounds on this beast. From there its just a short length to this "tee" that some of you speak of. On my engine, it sits down by the rest of the vacuum lines that come from the front axle (or at least im preatty sure). Almost right next to the blue vacuum line that im trying to figure out if it connects to anything or not. From this "tee" it splits off and goes straight around too the charcol canister .. or at least i think that is what it is called on this vehicle... i could be wrong. Its the black cylinder that is directly to the right of this "tee". This black cylinder also has a vacuum line that runs all the way back too the feul tank. When its light outside again ill have too snap a few more pics and update this thread on this line, and the other one that splits straight up from the "tee".

I hope this information helps some of you out...
 
Last edited:
Is your jeep 4 x 4? I was thinking that might be the vac. line that opperates the 4 x 4
 
Muad'Dib said:
Just as an update, this thread seemed to help:

http://www.naxja.org/forum/showthread.php?t=50021

As stated in this thread also, the round "UFO" is a check valve and it doesnt connect to anything else at the other end.
Thanks again for everyones help.
Click to expand...

Yep that thread shows exactly what it is. Matthew has the right answer. I have a diagram in my FSM. For those of you that have it, its in the suspension and axle section. That particular "UFO" is a filter.
 
Anyone have any pictures or diagrams for the heater (HVAC) vacuum on the 85 XJ with the 2 canisters (look like coffee cans) mounted over the front right wheel. I, too have a mystery blue line that hooks to nothing. I have 4WD (Command-Trac) and cruise control (that don't work). Thanks!!!!!!!
 
After doing some research, I have come to determine that the blue line is not hooked to anything. It is however a vent line and should have a one way check valve on it. I still need the pictures or diagrams from my model XJ though. Thanks.
 
tow2topgun said:
After doing some research, I have come to determine that the blue line is not hooked to anything. It is however a vent line and should have a one way check valve on it. I still need the pictures or diagrams from my model XJ though. Thanks.
Click to expand...
I don't think you want a check valve on the vent, or the 4WD won't work right. Originally it had a filter.
 
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