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Need help with 84 CJ7 vacuum hoses!!!!

38K views 106 replies 11 participants last post by  Crazy_Jeeper_7 
#1 ·
I am trying to get my 258 4.2L amc engine to run, and the first to tackle are the vacuum hoses and where their correct locations are. When I got the jeep there were zero hoses hooked up, so thought that maybe hooking the hoses up correctly could be vital in this rebuild. Anyone have any diagrams/photos/videos that point me towards the right path. Suggestions and advice are appreciated.
 

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#96 ·
Just go to Dropbox.com and register an account. Then create a folder and upload the document into it. Then from your main page that displays folders, scroll over the folder you want to share and over to the right a link of chain button will appear. Click on that and a pop up window will come up that says share link to "folder". Then click the Get link button and that should copy the link to your clipboard. Then just paste that link into the forum. That should allow people to go to that folder to look at the file.
 
#98 ·
This thread has been extremely helpful. I installed an EMPI 32/36 2BBL carb on my 78 stock 258 and now I have oil spraying everywhere at higher speeds. The CTO is plugged by my grandfather, the canister is 36 years old, and the hose tee'd off the new PCV valve to the canister collapses when it's idling. It idles smooth and runs fine, but why is oil pressure at 5psi idle and at 60psi driving and spraying out of the dipstick tube? There's even oil making it thru the valve cover breather tube into the air cleaner assembly. Also, what is the mechanism below the carb but above the EGR? One hose is plugged and the other hose leads to the cap of the canister from this mechanism.
 
#99 ·
I would first think maybe the oil filter was plugged.

The small line to the canister comes from the CTO on the intake by the carb. CTO needs ported vacuum to turn the canister on. Not your oil blowing issue likely.
 
#100 ·
Mike,

On the mechanism below the carb off the side of the manifold, but above the EGR, it has two lines. The top 6mm hose is plugged to the top of the canister, and the bottom 4mm hose is plugged with a screw and some RTV.

I did locate my CTO though; both lines are plugged.

The EGR valve port has nothing connected to it either.

Both my manuals got packed up for my current move.

So, my question is, with the float bowl hose, fuel vapor line to the tank, the T'd 8mm hose from the PCV, and the mystery mechanism 6mm line all hooked to the canister, is that creating a negative vaccum since the CTO is plugged?
 
#101 ·
Sorry, I got mixed on the parts. The canister gets a large vent from the carb float bowl. It also gets one from the gas tank. The valve on top of the canister purges into the PCV system. The small line off the top of the canister turns it on. It should come from a ported vacuum source so it only turns on at speed.

I think you are describing a manifold vacuum source going to the small 'turn on' line up top? If so, it will cause a vacuum leak at idle making the carb real hard if not impossible to tune.
 
#102 ·
So, after some research, I found that the mechanism below the carb, but above the EGR is the Manifold Vacuum Fitting. I have two 4mm hose hookups on mine but I cannot find a schematic that shows what they are suppose to be hooked too. With the engine running, they both have a vacuum. If I plug one of them with my finger, the engine idle doesn't change. If I plug them both, the engine idles rough and slow. I plugged one of them and put a vacuum valve on the other. I know this isn't how they are supposed to be hooked up and would like to fix this. Just short of rebuilding the engine, I have got to find out where the oil is coming from at speeds above 35mph.
 
#103 ·
One goes to the distributor for manifold vacuum advance and the other usually goes to a power brake booster. If you use ported advance, they need to be blocked.

Your engine will not run right with these open. They create a massive vacuum leak. They must be blocked off, then the carb mix will need to be reset from the sounds of it. Especially if someone tried to tune the carb with these open.

A vacuum leak like that makes the idle go high, so if the carb was tuned that way, blocking them should make the idle go way down and the carb needs to be reset.
 
#105 ·
Thanks Matt and Mike! I am not running the factory air cleaner; i am using the EMPI air cleaner assembly with a K&N filter.

So I need to plug both of the manifold vacuum hoses?

The EMPI has the vacuum advance port for the distributor so that is hooked up. I pulled out the instructions for resetting the EMPI carb so I'll plug the hoses from the manifold vacuum and reset the carb to factory settings and then fire it up to check timing. While I'm at it I'll pull the #1 plug and check the TDC versus the distro cap.

Matt, i'd still like the vacuum schematic; i used to run the stock air cleaner and had a snorkle hooked up to it which I might go back to one day.
 
#107 ·
Thanks!
 
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