'81 Jeep J10 258 6 Cylinder Stalls and won't idle

[masnocab]

First post to FSJN and I really am new to fixing my own vehicles so thanks for any help and your patience as I pickup a new hobby. I have a 1981 Jeep J10, 258 6 cylinder, 4 speed trans. When I first got it in December it ran great and idled good. I decided to give it a tune up, not knowing its history. I did new plugs, wires, rotor and cap. It may have been coincidental, but about a few weeks after the engine would stall if I didn't keep my foot on the gas pedal. So now it won't idle and stalls at stops. I did some research and found different articles on the carter carb venturi tubes potentially being an issue. So i took did this fix, http://www.jeeptech.com/engine/carter.html and cleaning with carb cleaner hoping it help. Either I did it wrong and didn't get it cleaned out properly or I have some other issue. Is it my timing or vacuum or what? Any help would be appreciated before I just take to my mechanic and pay money to fix... Thanks!

[BCRAWLER]

Did you check all vacumm lines. Possibly one has come loose.

[masnocab]

No... I will check them, but there are quite a few and i see a few spots where it seems like hoses maybe missing? I attached a couple pix to see what y’all think?

[will e]

Most likely it is a vacuum line issue. It's hard to tell from the pics. Start at the carb and the manifold tree and trace each vacuum line just to make sure it is connected.

The two largest will be to the brakes and the PCV. Check these first.

[masnocab]

Ok. Added a few more of shots with no hoses. Should these be plugged or add new hose? Also the one from the valve cover to the air filter is really loose and just rests there.

[tgreese]

Any port that vents engine vacuum to the atmosphere must be plugged. Start with that.

Changing/disconnecting the vacuum system is tricky. Fixing the vacuum system is easy - just put it back like the factory intended. In this era, the emissions devices and vacuum plumbing changed annually, and the plumbing was different depending on the model and equipment, and even by locale (California and export are different). You can look the TSM for your year for a table in the emissions section that shows which devices were used for your model and equipment. Then, each system is described in function and operation in the text of the section. By '81, there should be a vacuum diagram in the TSM for your year specific to your model and equipment.

http://www.bjsoffroad.com/1981-Jeep-Fac ... _1052.html

The vacuum diagrams for 1980 are online, like here http://oljeep.com/gw/vac/80/80_258_49_S ... TDCool.jpg However, the plumbing will likely be different for 1981 (which is not online). You need to buy the book. You also need to know if your truck is a Califonia model or for the 49 states, and whether you have heavy duty cooling or not.

CD format at RockAuto https://www.rockauto.com/en/moreinfo.ph ... 94&jsn=369 - act fast, they seem to be discontinued as supply runs out. You need th factory manual - the Haynes or Chiltons manuals won't help you.

[masnocab]

Thanks for the input... I have an ‘81 TSM and I believe I have the right diagram. There is one hose on the passenger side that isn’t connected... I am not certain where it goes even looking at the diagram, so I just plugged it. On the manifold side there are quite a few ports that I plugged... lastly on the valve cover, i replaced the two rubber grommets on for the hose that goes to the air cleaner and the on that goes to the pcv valve. Now they are sealed nice and tight... I Started it up and it still stalls... I am wondering if it is really is vacuum because prior to the tune up, it never did this... I feel like it is starved for fuel or something since as soon as I let off the gas it stalls. Not sure whats next...

[tgreese]

Realize that vacuum only comes from the manifold or carburetor base, never from any of the ehissions devices. You can have vacuum coming from an emissions device, but it would have come from the manifold, through the device and to the hose or whatever.

IMO the key to all this is understanding what the devices do. Then you can recognize where the hoses are coming from and connect them as they should be, or remove them if you want to remove that functionality.

If you have the list of devices in front of you, you can look at your disconnected hose, for example, and see if you can assign it to one of the devices. I would guess (!!!) you are looking at the vent line coming from the fuel tank. That hose goes to the vapor recovery canister (charcoal canister) so the fumes can be caught and saved to be burnt next time the engine runs. The canister is frequently removed as part of the evil smog systems, or for esthetic reasons (both wrong-headed IMO). Vapor recovery is a benign system with many advantages and few demands, with zero effect on performance.

If the line is actually the vent line, plugging it without fitting a vented gas cap could make the engine quit suddenly for no apparent reason. You need a vent to the tank that admits air to relieve the vacuum above the fuel created by the fuel pump drawing out fuel. Maybe not ... if the fuel pump return hose is open or the hoses are leaky, plugging that line won't change anything.

My opinion - likely you screwed up the carburetor internally, or created a leak around the carburetor base gasket. Vacuum leaks make the mixture overly lean, which can lead to a stall or backfire through the carburetor.

Do you understand how the PCV system works? It takes filtered air from the air cleaner, passes it through the crankcase, and sucks it into the manifold (along with the crankcase vapors) where they are burned by the engine. You have both an air-in and an air-out connection to the valve cover, in the case of the 258. Lots of valuable insight in the TSM, including a description of the PCV system.

[tgreese]

Can you host the pictures somewhere online, and either link to them or hotlink? I expect the forum limits you to that small picture size. 600x800 or even a little larger is a good size for pictures; large enough so we can see detail.

For example -

[tgreese]

...

[tgreese]

[masnocab]

Thanks tgreese. Very helpful to look at each area and component. Knowing what each does has started to expand my limited knowledge of engines. Working to learn more for sure... I did find that I am getting a fuel leak on the sides of the carb. See the video in this link. https://share.icloud.com/photos/0ETRmzc ... IdLmA#Home

I have decided to replace the carter carb vs. rebuilding. I bought a crown automotive replacement vs. the weber that may have recommended. Only because I wanted something as close to original as possible, but one that should be an improvement. Does anyone have experience with a crown and any advice for a good swap?

[masnocab]

Also as suggested, I posted pix online...

https://share.icloud.com/photos/0ogan-z ... rt_Gratiot

[tgreese]

Mmm. Links don't work. Likely you need to set permissions so that everyone can see them.

[masnocab]

Hmm. I posted it to iCloud. Are you trying to access with PC? Not sure why it wouldn’t work...

[BCRAWLER]

I can access them from cell phone, just takes a while.