Bad to worse, 2.8 V6 engine woes - 1986 Jeep Cher - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 07-19-2006, 10:53 AM
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Bad to worse, 2.8 V6 engine woes - 1986 Jeep Cher

Well, the fun continues. I bought this as a non running vehicle that supposedly ran good. But it clatters like a sewing machine. I changed the oil and filter and started it up again, no change. After adjusting the timing and the right cylinder bank valve lash I parked it.

Next day it will not start. Tries, but will not stay running. AFter running down the battery and playing with the distributor position I checked the exhaust manifolds. THe left side was quite warm but the right side (the side I did the valve lash adjustment) was just barely warm. SO
I take the valve cover off again and check the valve lash again. Most of the pushrods are loose so I again readjust them. Keep in mind that I have
now tightened the rocker arm hold down nuts three turns from their original positions several days ago. I turned the engine over manually after removing the plugs and watched the rocker arms. They all move up and down about the same distance with one exception which I recheck and
find OK. It started to rain so I did not attempt to start it up.

I would like to know why the rockers needed readjustment again, does it seem likely the hydraulic lifters are all collapsed? Does it seem reasonable that this problem is related to the black smoke, poor idle (and sooty spark plugs)?? I was told by the PO that this engine ran fine other than "leaking a little oil" (gushing would be my description, the rear seal is shot!!). I have not checked compression yet, wanting to get the valve lash taken care of first. I have also not attempted to adjust the
left valves because I wanted to make sure I was doing it right in the first place...

I would like to at least get it running well enough to take it down the hill to my mechanic.
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post #2 of (permalink) Old 07-19-2006, 01:10 PM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep Cher

Sounds like a possible shot motor. Gushing oil would be part of the lifter problem: no/loss of oil pressure. You may want to back off the rocker adjustment: if pressure builds up and lifters refill you may push valves into pistons. It may be something simple like a oil pressure relief valve the is broken or a clogged pump strainer.
I think I would look for a way to build up oil pressure as a very first step. Oil will quiet the engine, fill up worn spaces, and protect what is left of the internal parts. Black smoke: check for carb leakage, non working float.
If you are unsure of the damage you may do trying to start this Jeep, tow it down to a mechanic. PS: tell him what you did to the rockers.
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post #3 of (permalink) Old 07-19-2006, 08:25 PM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep Cher

As far as I remember, you are supposed to adjust the valve lash on a 2.8 with the engine at idle. Good auto parts stores (not chains) sell oil deflectors so you don't take an oil bath. However, you only adjust the lash as a last resort.

Other than that, I second what tincan said. Good Luck!! [img]/ubbthreads/images/graemlins/smile.gif[/img]
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post #4 of (permalink) Old 07-24-2006, 11:02 AM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep C

Well thanks for the posts. I went back and unadjusted all the valves I did. Now it starts and runs. While I was at it I checked compression and found that all cylinders are about 155PSI. Oil pressure (hot) runs between 35 and 60PSI, depending on engine speed. I drove it around a few miles and after it is running a couple of minutes seems to go pretty well (choke does not seem to work). I have to set the idle to 1200 RPM though to make sure it doesn't quit. It will burn rubber from start and going up an 11 per cent grade at 53 MPH it holds speed, so I think the engine is pretty solid, despite all the noise it makes. I got it down to my mechanic for a going over and he said, "yep, sounds like a 2.8 Jeep". The carb is a problem right now because the previous owner(s) took all the vacuum hoses off and some of the vacuum gizmos are missing. I just bought an official AMC JEEP service manual off EBAY and am hoping that it shows pictures. The under hood picture and the Haynes manual picture of the vacuum hose connections is useless. One problem is that they use "ABCDE" for the vacuum ports on the carb but don't identify which ones are which. DOES ANYONE HAVE THE ABILITY TO TAKE DIGITAL PICTURES OF A 2.8 STOCK SETUP of the underhood vacuum hose routing and connections?

I think this is the only way I will ever be able to figure it all out. Especially the correct vacuum connection to the distributor and the 5 way valve that bolts into the intake manifold in the front of the engine.
post #5 of (permalink) Old 07-24-2006, 08:15 PM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep C

Well, having been a 2.8 XJ owner myself (I bought one new in 1986 and had it for 18 years), I definitely know where you're coming from; a 2.8 XJ has alot of vacuum tubing. I've looked for my old marked up copy of the Haynes manual that I had when I owned it but I must have given it away. I do remember that although the Haynes vacuum diagram is accurate as far as how the vac tubing all connects but it is not so accurate on the actual location of all those little connectors in the engine bay. Wish I could be of more help there.

After you drive the Jeep around for awhile, does the choke open up? If it does, then the choke pull off vacuum tubing is right.

Sorry my memory isn't would think after 18 years of maintaining the 2.8 I would recall more. Hopefully, the AMC Service manual can set you on the right track. Good Luck!! [img]/ubbthreads/images/graemlins/smile.gif[/img]
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post #6 of (permalink) Old 07-25-2006, 12:18 AM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep C

vacuum hose nightmare!, the 86 Jeep 2.8 was one of the worst ever, good thing they went to FI the next year.
Many of those hoses had to do with closing and opening the warm air door in the air cleaner, some for EGR and choke.
The choke and vacuum advance are really the only ones you need to worry about, with missing components you could be in for quite hassle getting it all right, and finding a mechanic with the knowledge (memory) of that set up will not be easy. The jeep manual is not going to help you much, I can tell you that much.

Make sure you have vacuum at the choke break, as soon as the engine runs. Ported or direct manifold vacuum will work at the distributor advance. Do not run direct vacuum to the ERG valve, this will kill the engine at idle.

As far as the warm air door, and other devices, you can probably live without them

Good Luck
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post #7 of (permalink) Old 07-30-2006, 09:38 PM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep Cher

On my old 2.8 which is now gone to be a teenager's first vehicle, the oil seal started leaking. It was not just a matter of replacing it as the main bearings were "wallowed" out causing the crank to wobble and wear out the seal. It ran fine other than an oil leak. My biggest mistake ever was rebuilding that engine and not just keeping a case of oil in the back. Take it from me, once the engine is gone, upgrade to the 4.0. I loved that old Jeep but never again will I sink that much money into a 2.8.
The vac lines? Good luck is all I have to say. I will tell you this after many years of tinkering with that old Jeep, you can remove 1/2 of the lines and it will run fine and pass inspection. Don't ask me which ones or how I did it but I would just plug and stick until it sounded ok.
That old carb will drive you nuts. You might look at a Camaro with the 2.8 or Blazer or Fiero and pull the fuel injection for a swap. I never did it but I have read it makes the 2.8 come alive. Look up a 60 degree v-6 and you will find lots on that engine.
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post #8 of (permalink) Old 07-31-2006, 02:40 AM
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Re: Bad to worse, 2.8 V6 engine woes - 1986 Jeep Cher

Hey Stump, good to see tour still alive!

And mariner: though I know you didn't specifically ask for this, here's soms nice suggestions for a worn and butchered 2.8:
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