How tired is it?

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Johnzi10
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How tired is it?

Post by Johnzi10 » Thu Jun 17, 2021 3:08 pm

My 89 Wagoneer had 92k miles.I’ve put 400 shaking it down after it sat 5 years. After trying to upgrade to a TFI, which fried fuse links, I’ve switched back to the original coil. Bought a compression gauge, and checked the 360 as I was retapping the plugs to OE spec.here are my numbers:
1-95. 2-120, 3-110,4-90,5-110,6-110 oily, 7-120,8-130 oily.
They were brand new plugs, ran at high idle for 10 minutes at wrong gap, but ran smoothly. I’m guessing the oily plugs could be valve stem seals if I’m lucky.
Was not planning a swap at this time. I’m looking for others experience, comments about how tired/what to expect from the old girl.
2020 Cherokee Limited v6. Wife’s Jeep
2002 Grand Cherokee Laredo Daughters Jeep
1998 XJ Cherokee “the Ghost”
1989 Grand Wagoneer my Covid mental health medicine

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Stuka
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Re: How tired is it?

Post by Stuka » Thu Jun 17, 2021 4:38 pm

All of those numbers are pretty low. Good numbers are 150-160 for our low compression engines. Its not that you can't continue to drive it that way, but it most likely smokes when getting on the HWY, and obviously down on some power.

Out of curiosity, when you first went to start it after sitting for some many years did you turn the engine over by hand or did you use the starter? What can happen is the rings can develop rust on them after sitting for extended periods, locking them to the cylinder walls. If you try to turn over by hand, you can't. So typically spraying some oils into the cylinders will loose them up. However, if the starter is used, it can break the rings. Which, results in low compression.

Oily can also suggest bad valve stem seals or a lot of blow by pushing oil up through the PCV.

As for the TFI upgrade, blowing the fusible links suggests you had a short someplace.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


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Johnzi10
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Re: How tired is it?

Post by Johnzi10 » Thu Jun 17, 2021 8:26 pm

Used the starter☹️. Have to find the short and see how it runs.
2020 Cherokee Limited v6. Wife’s Jeep
2002 Grand Cherokee Laredo Daughters Jeep
1998 XJ Cherokee “the Ghost”
1989 Grand Wagoneer my Covid mental health medicine

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Stuka
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Re: How tired is it?

Post by Stuka » Thu Jun 17, 2021 8:59 pm

Johnzi10 wrote:
Thu Jun 17, 2021 8:26 pm
Used the starter☹️. Have to find the short and see how it runs.
Doesn't mean you were the cause of the issue, its possible the compression was low five years ago. If its just a weekend cruiser for you, it may do that fine for a long time. Just keep in mind a rebuild/replacement may be in its future.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


rocklaurence
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Re: How tired is it?

Post by rocklaurence » Fri Jun 18, 2021 6:32 am

Get it up and running, have fun and then decide where you want to go with your project. :-bd

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tgreese
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Re: How tired is it?

Post by tgreese » Fri Jun 18, 2021 7:15 am

If you want to learn more about your engine's condition, I suggest you do a dry test and a wet test and compare the numbers. You probably tested the cylinders dry, where you prop the carb flap open, disconnect the coil and crank the engine.

A wet test puts some oil on top of the rings. If the rings are leaky, this will raise the compression reading obviously, like 20-30 lbs maybe. If there is no change, leakage is probably through the valves.

However, those readings look more like ring wear than bad valves. Typically with a bad valve you'll see one or two really bad cylinders, and the rest will be normal-ish (like 130-150ish). Especially with oily plugs, that looks to me more like a 192K engine than a 92K engine. When you get up around 150K-200K, the maintenance should really matter in the wear of the engine. A high-mileage engine that's had frequent oil changes and kept in tune might be a lot better than what you see. I'd think that some serious neglect would be needed to wear-out one of these engines in less than 100K miles, if actually possible.

I'd also look at hot idle oil pressure. These engines often have oil pressure that goes to near zero at hot idle, when well-worn. As a rule of thumb, you'd expect something like 10 psi per 1000 RPM, at full operating temperature. This is a worse problem than the compression, since it will eventually cause rod bearing failure. The low compression will probably putt along for many miles.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
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Johnzi10
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Re: How tired is it?

Post by Johnzi10 » Fri Jun 18, 2021 1:57 pm

I’ve had good oil pressure if I can believe my gauge, about 10lbs per 1000 rpm. I did a dry test, so I hope my motor can putt along till I want to do something, don’t have to.
2020 Cherokee Limited v6. Wife’s Jeep
2002 Grand Cherokee Laredo Daughters Jeep
1998 XJ Cherokee “the Ghost”
1989 Grand Wagoneer my Covid mental health medicine


letank
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Re: How tired is it?

Post by letank » Sat Jun 19, 2021 7:33 pm

I have about 130 on my 360, it is still pulling fine at 228k on mostly original anything... the 90 psi is for sure not good. thd othef at 349k is atill ok albeit the blow by...

bad valve spring... can come to mind!

but waiting for your results on wet compression with throttle kept wide opened
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (227 Kmiles... the running test lab)
See Engine bits , Fuel and brake lines, Body work, Trany and TC

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tgreese
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Re: How tired is it?

Post by tgreese » Mon Jun 21, 2021 7:12 am

Johnzi10 wrote:
Fri Jun 18, 2021 1:57 pm
I’ve had good oil pressure if I can believe my gauge, about 10lbs per 1000 rpm. I did a dry test, so I hope my motor can putt along till I want to do something, don’t have to.
If you had zero pressure, the lifters would not pump up and there would be a constant clatter while the engine is running. The electric gauge in the dash is advisory at best, both very slow reacting and inaccurate. Might be worthwhile to buy an inexpensive mechanical gauge and see what it reads at hot idle. https://www.summitracing.com/parts/sum-g2934
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.


Topic author
Johnzi10
Posts: 148
Joined: Wed Nov 25, 2020 9:43 pm
Location: Northern Kentucky

Re: How tired is it?

Post by Johnzi10 » Sat Jun 26, 2021 12:49 pm

Running real well now with new plugs, wires and cap. Starts well, no stalling, good power. I am moving on to other needs, just want it reliable, not a rod or trail rig.
2020 Cherokee Limited v6. Wife’s Jeep
2002 Grand Cherokee Laredo Daughters Jeep
1998 XJ Cherokee “the Ghost”
1989 Grand Wagoneer my Covid mental health medicine


candymancan
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Re: How tired is it?

Post by candymancan » Sat Jun 26, 2021 6:27 pm

Did you check compression with all the plugs removed. And by cranking until it doesnt go up anymore ? Also did you stick open the throttle plate to wide open ? Thats one mistake people do. Not openeing the throttle to max will give you low readings.

If you did then.. i would say that engine is tired.. for only 95k thats surprising. My 360 has 145k now. Ans when i checked compression all of then were 150.. but number 8 was unfortunatly around 120 or 125 i believe ?

If compression doesnt go up with oil in the cylinders then the problem is most likely valve related and not cylinder head related. My #8 didnt go up with oil.. So that leads me to believe its valve related.. most likely cam shaft lobs worn on #8
1998 Jeep Grand Cherokee 5.9L Limited 197k
1998 Jeep Grand Cherokee 4.0 I6 laredo 324k
1990 Jeep Grand Wagoneer 141k


Topic author
Johnzi10
Posts: 148
Joined: Wed Nov 25, 2020 9:43 pm
Location: Northern Kentucky

Re: How tired is it?

Post by Johnzi10 » Sat Jun 26, 2021 7:55 pm

Only checked one cylinder at a time, others had plugs in. I did not open the throttle plate. I hope all my readings were low!
2020 Cherokee Limited v6. Wife’s Jeep
2002 Grand Cherokee Laredo Daughters Jeep
1998 XJ Cherokee “the Ghost”
1989 Grand Wagoneer my Covid mental health medicine


candymancan
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Re: How tired is it?

Post by candymancan » Tue Jun 29, 2021 8:11 am

You did it wrong then. Redo it. And this time jam a wrench or something or have someone push th3 pedal to the floor.

Keep it wide open. Dont release and stomp on the pedal again as that will shoot gas into the intake and cylinders and wash out your cylinders. Just keep it open till youre done with all 8.

The engine has to be able to breathe when you check compression to get a correct reading. I imagine when you redo this your comoression readings will jump up 50% or more
1998 Jeep Grand Cherokee 5.9L Limited 197k
1998 Jeep Grand Cherokee 4.0 I6 laredo 324k
1990 Jeep Grand Wagoneer 141k


Topic author
Johnzi10
Posts: 148
Joined: Wed Nov 25, 2020 9:43 pm
Location: Northern Kentucky

Re: How tired is it?

Post by Johnzi10 » Tue Jun 29, 2021 10:26 am

Thanks, will do!
2020 Cherokee Limited v6. Wife’s Jeep
2002 Grand Cherokee Laredo Daughters Jeep
1998 XJ Cherokee “the Ghost”
1989 Grand Wagoneer my Covid mental health medicine

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