Another Vacuum line question (vacuum advance)

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prairiejeeper
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Another Vacuum line question (vacuum advance)

Post by prairiejeeper »

I am attempting to fix a rough idle, that often dies if put into gear before it is up to temp on my 1980 J with a 360.

What I found was the previous owner butchered the vac systems, The CTO valve on the thermostat housing has three ports with no hoses to be found and according to the manual that controls my timing advance when cold/ hot. I have a feeling it might help keep my idle up when shifting into drive or reverse.

I will worry about the other vacuum/evap stuff as I come to it but I want to start off simple and work my way into the rest of the system. I still have to come up with a reliable evap delete since the canister and all hoses are missing as well which I need to remedy at some point to keep the fuel consumption down.

I am hoping someone has a picture that would help but some routing details would work too. I have been going over the repair manual and it has great information if I were looking at a vehicle right from the factory, but it doesn't help me when most of the items described are missing. I am not even sure what the distributor is hooked up to at the moment.

30 years of previous owners trying to out smart the manufacturer leaving me with a headache :banghead:

FSJ Guy
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Re: Another Vacuum line question (vacuum advance)

Post by FSJ Guy »

http://oljeep.com/gw/vac/GW_vacuum.html

And scroll down to your year.
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shimniok
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Re: Another Vacuum line question (vacuum advance)

Post by shimniok »

This may help in understanding all the components and how they work: http://tc.wagoneer.org/2012/08/fsj-v8-v ... uting.html
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Strode182
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Re: Another Vacuum line question (vacuum advance)

Post by Strode182 »

shimniok wrote:This may help in understanding all the components and how they work: http://tc.wagoneer.org/2012/08/fsj-v8-v ... uting.html
Michael's tutorial that he linked is a must. I finally got to tell him in person how much it helped me understand all the vacuum systems. Thanks again, Michael.
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shimniok
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Re: Another Vacuum line question (vacuum advance)

Post by shimniok »

Glad to hear it helped!! :)

sent from my MotoX
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'86 GW "Troubled Child" tc.wagoneer.org
360, TBI, 4" Skyjacker, 33" BFG MTs, WT D44+ARB, WT AMC20 + LockRight, CB 2m 6m 70cm, K0FSJ
The world's first Robotic Full Size Jeep!
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Tatsadasayago
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Re: Another Vacuum line question (vacuum advance)

Post by Tatsadasayago »

Also, for when you aren't going into the emissions testing station:
Consider using manifold vacuum instead of ported.
You set the base timing the same way (Vacuum line disconnected) and fine adjust using a vacuum gauge for highest reading at idle.
Your engine and fuel money will thank you.
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Topic author
prairiejeeper
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Re: Another Vacuum line question (vacuum advance)

Post by prairiejeeper »

Thanks Tat, that is kind of where I am trying to brain storm. Not that we have smog testing in Sask - "emissions control, we don't need no stinkin' emissions control!" I am just trying to solve which source I should use for my dizzy to fix my rough idle and stalling while cold issues. It is a temporary solution since this truck only needs to run in and out of the shop until I get the truck ready to be a daily driver.

Topic author
prairiejeeper
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Re: Another Vacuum line question (vacuum advance)

Post by prairiejeeper »

One last question, the only part of my vacuum system I can't sort out is my Cruise Control. The line to the ball on the firewall is there, but the other line is just left open. Where do I find cruise information? The speedo doesn't work so I was thinking about bypassing the cruise, if I can find the right cable.
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Tatsadasayago
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Re: Another Vacuum line question (vacuum advance)

Post by Tatsadasayago »

Rough idle and stalling while cold is typically a choke and fast idle speed stepper related issue.
If the choke is not setting at startup, the engine will run lean and often stall if a load is placed upon it. The carb warm air heater hose and vacuum controlled diverter valve (Mounted inside the air cleaner snout) go a long way toward keeping a cold engine running.
Vacuum advance doesn't apply to cold starts on a stock AMC engine after the mid 70s since the CTO blocks the signal until the coolant temp rises above 140-160f. Once it opens then the advance begins working.
I don't have the vacuum diagrams on hand but recall the cruise control unit getting it's vacuum from ball on the firewall and also feeds the transfer case shifter and the heater actuators. On non-cruise equipped models, the round hole is still there but the nipple is not...in other words, it's blocked off.
olejeep has a few factory service manuals available and depending on your year, you may be able to find something that applies. I recall the cruise system being essentially the same from 74-79 so if yours falls within that range, the info applies.

Good luck!
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Topic author
prairiejeeper
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Re: Another Vacuum line question (vacuum advance)

Post by prairiejeeper »

I fixed the idle as far as vacuum system can go. The hose for the diverter valve was gone, the CTO blocks are bypassed and I only see a vent line to the t-case. I don't think the 208 runs a vacuum system, as far as the olejeep manuals show I think I have all the info they can give. But still not sure which way I want to go with the cruise
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carnuck
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Re: Another Vacuum line question (vacuum advance)

Post by carnuck »

One hose goes to the brake pedal switch to kick the cruise off when brakes are applied.
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