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vac, valves, carb, i don't know anymore


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ok so this all started on aug 22nd when i rebuilt my carb, i slapped it on saturday but spent all day tryin to get it right, well my dad kinda sorta got it right but it clattered so tonight i started adjusting valves after i rerouted some vaccum lines, now my MJ don't stay runnin, it smells like i have oil bein burnt off an exhaust pipe and it runs rough as anything. I don't know what my next step would be other than to buy another engine, i even hooked a vac gauge to a vac line and the readin according to the book was weak or broken valve springs....well they're not broken i can tell ya that and they don't seem weak; again i just don't know what my next troubleshooting step would be, i'm bout ready to say screw it and either sell my MJ or buy another junkyard motor that'll last me another year

 

Redwolf

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Please describe how you adjusted the valves.

 

You probably do have oil burning off the exhaust manifolds. To adjust the valves, you had the valve covers off. I'm sure some oil dripped onto the manifolds.

with the number one pistion at top dead center i adjusted number 1 5 and 6 intak valves till there was no movement on the pushrod then tighten the nuts 1 1/2 turns then i adjusted 1 2 and 3 exhaust valves the same way, with number 4 pistion at TDC i adjusted 2, 3 and 4 intake valvs then i adjusted 4 5 and 6 exhaust valves, all valves where adjusted till the pushrod had no movement and tighten an extra 1 1/2 turn just like the haynes manual says, my alldata program at work says, the only way i haven't tried is with the engine running,

 

Redwolf

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If your truck has hydraulic lifters you have to adjust the valves with the engine running. The lifters have to be "pumped up" by the engine oil pressure. On older engines it is common for the lifters to leak down (collapse) when the engine is turned off.

With the lifters leaked down, once you go past no movement on the push rod and tighten more you are bending or crushing the push rods.

Take your valve cover back off, loosen the rockers, start the engine and adjust the valves again. Wouldn't hurt to pull and inspect the push rods to see if any are bent.

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with the number one pistion at top dead center i adjusted number 1 5 and 6 intak valves till there was no movement on the pushrod then tighten the nuts 1 1/2 turns then i adjusted 1 2 and 3 exhaust valves the same way, with number 4 pistion at TDC i adjusted 2, 3 and 4 intake valvs then i adjusted 4 5 and 6 exhaust valves, all valves where adjusted till the pushrod had no movement and tighten an extra 1 1/2 turn just like the haynes manual says, my alldata program at work says, the only way i haven't tried is with the engine running,

But were you certain that #1 was a TDC on the firing stroke, and not the exhaust stroke? The lifters have to be on the cam base circle, not on the lobe (lifted). The crankshaft goes around twice for each one revolution of the camshaft, so it's not enough to just align the timing mark -- you have to verify that you're on the compression stroke and not the exhaust stroke.

 

The way you did it is the way the Jeep FSM says to do it -- but you do have to be certain which stroke you're on.

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Why is it that almost every time I cite the FSM somebody chimes in with "That's impossible" or "That can't be right." WTF? Do you guys think I make this stuff up?

 

I have the FSM for the '86 - '88 MJ and for the '86 - '88 XJ. If I cite something from the FSM, that means I looked it up, because I DON'T want to be giving out incorrect information. Yes, I know small-block Chevy V8s were adjusted while running -- I've done it many times. That does not change the fact of what the FSM says is the correct way to adjust the valves on the 2.8L engine. Apparently Haynes agrees. So does Chilton. So maybe -- just maybe -- that's the right way to do it.

 

I don't know why I waste my time trying to help people here, I really don't. People who weren't even born when I started wrenching ALL know so much more than I do I'm obviously out of my league.

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Why is it that almost every time I cite the FSM somebody chimes in with "That's impossible" or "That can't be right." WTF? Do you guys think I make this stuff up?

 

I have the FSM for the '86 - '88 MJ and for the '86 - '88 XJ. If I cite something from the FSM, that means I looked it up, because I DON'T want to be giving out incorrect information. Yes, I know small-block Chevy V8s were adjusted while running -- I've done it many times. That does not change the fact of what the FSM says is the correct way to adjust the valves on the 2.8L engine. Apparently Haynes agrees. So does Chilton. So maybe -- just maybe -- that's the right way to do it.

 

I don't know why I waste my time trying to help people here, I really don't. People who weren't even born when I started wrenching ALL know so much more than I do I'm obviously out of my league.

 

ok here's where i'm at now, the MJ runs, if i gun the gas it clatters, dad worked on it this mornin and adjusted the valves again but only turned then 3/4s a turn,

 

Redwolf

 

 

 

OK.

 

Apparently it's not working.

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How's your oil pressure?

 

How many miles on the 2.8?

 

How have you determined that the lifters have not collapsed or are pumping up?

i don't know how to test the oil pressure and i believe it was 150,000 somethin miles and i believe all the lifters are pumpin oil, there is no dry spot on any lifters,

 

Redwolf

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How's your oil pressure?

 

How many miles on the 2.8?

 

How have you determined that the lifters have not collapsed or are pumping up?

i don't know how to test the oil pressure and i believe it was 150,000 somethin miles and i believe all the lifters are pumpin oil, there is no dry spot on any lifters,

 

Redwolf

 

I'm suggesting that your lifters may not be able to maintain an adjustment hydraulically any longer.

 

 

150K for 2.8 may be near it's life's end.

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How's your oil pressure?

 

How many miles on the 2.8?

 

How have you determined that the lifters have not collapsed or are pumping up?

i don't know how to test the oil pressure and i believe it was 150,000 somethin miles and i believe all the lifters are pumpin oil, there is no dry spot on any lifters,

 

Redwolf

 

I'm suggesting that your lifters may not be able to maintain an adjustment hydraulically any longer.

 

 

150K for 2.8 may be near it's life's end.

 

it could be, i did pull that engine out of a junkyard, could i just buy the heads and fix the issue or would that be a new engine thing?

 

Redwolf

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When I did the valves in my old 2.8 I did it per the chiltons book and it was all messed up . The book was for a S10 2.8 of same era but it had me IIRC like 2turn past zero lash or some thing which was way past my "been doing this for years gut feeling" but did it anyways and it ran like poo so I did it all over by feel and IIRC only went a 1/4 to 1/2 past zero lash and was perfect . The only vehicle I ever messed with that needed to be adjusted while running were the old chevy straight 6 , though I have done it on some random stuff . If the lifters are collapsing try running some thicker oil and see what happens

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i'm done adjusting valves, i'm done playin with the carb, i noticed this today when i was a wendys in the drive thru, my engine knocks like a rod is knockin :(

That was the typical mode of failure for the 2.8L.

 

Back when Jeep first started using the 2.8L in the 1984 Cherokee, I was good friends with the service manager at the dealership where I bought my '88 Cherokee -- and where I had bought several AMC cars previously. I hung out in the shop fairly often in those days, and it was rare to come in and NOT find at least one Cherokee 2.8L with a connecting rod poking through the side of the block.

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yeah, i'm just hopin it don't go through, i wanna try to get either a new engine or a donor xj and do a 2.8 to 4.0 swap, but i have a feelin it'll be easier and cheaper to sell it to one of the idiots around here,

Respectfully, you DON'T want to do a 4.0L conversion. Not on an '86. You want to do a GM 3.4L conversion. You won't be needing to hack and/or hammer your firewall, and the block is the same basic 60-degree V6 as the 2.8L so the engine itself is a bolt-in conversion, and will take the same transmission you already have. You would have a choice of staying with your carburetor, or keeping the GM MPFI and getting the engine room wiring harness to run it from the donor vehicle.

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redwolf,

 

you need to get someone who knows what they're doing to work on that thing.

i know i do cause it's apparent i don't know what i'm doin but i can't afford to have my truck worked on by a shop let alone have no vehicle for however long

 

yeah, i'm just hopin it don't go through, i wanna try to get either a new engine or a donor xj and do a 2.8 to 4.0 swap, but i have a feelin it'll be easier and cheaper to sell it to one of the idiots around here,

Respectfully, you DON'T want to do a 4.0L conversion. Not on an '86. You want to do a GM 3.4L conversion. You won't be needing to hack and/or hammer your firewall, and the block is the same basic 60-degree V6 as the 2.8L so the engine itself is a bolt-in conversion, and will take the same transmission you already have. You would have a choice of staying with your carburetor, or keeping the GM MPFI and getting the engine room wiring harness to run it from the donor vehicle.

 

alright, 3.4 conversion but didn't i need a different wireing harness when i swapped 2.8s? or would i only need the harness if i don't go carbed,

 

Redwolf

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