Compression check: please give me some good news

newoldjeep

newoldjeep

New Member
Joined
Jun 3, 2020
Messages
16
Location
Rockwood, Tn
Hi my 1st post here. I just bought my 1st ever Jeep a 2001 Wrangler 4.0 for 1000. it was low because A) it has 250k miles and it has a cylinder 1 misfire. Well I have replaced the plugs to Champion Iridium and a brand new coil pack that did not help. I checked the fuel injectors with a multimeter all with in range. So I did a compression test the results
cylinder 1 dry test one 95 test two 95 dry 145 and 120
2 170 175
3 175. 175
4 175. 175
5 175. 175
6 160. 165
Those results tell me cylinder 1 has piston ring problems please please tell me I am wrong. and there is another possible solution.
Thank you for any help in advance.
 
Ok your wrong 🤭

Could be rings. Look on the bright side, you got a grand in it. You can pull the head and check things out, heck you could rebuild it and still not have as much cha ching in it as some folks do.
 
  • Like
Reactions: Artsifrtsi
After a low compression test, I would try a cylinder leak down test. This will tell you if you have a ring problem exhaust valve, or intake valve problem. You can make a leak down tester from simple materials from air fittings and gauges. Search the internet on how to build and check. Low compression does not guarantee bad rings. If valves are leaking, you will hear air in the intake, exhaust, or blowing in crankcase. I had low compression on #3 with two different heads, and both were intake valve issues, not ring issues.

Also, welcome to the forum!
 
  • Like
Reactions: Chris
pagrey said:
What does this mean, I've read it a few times and I don't get it. What are 145 and 120?

Edit: to be clear you've listed the other cylinders as "5 175. 175" so why four different numbers on one?
Click to expand...
cylinder 1 was the only one that had shown low compression so it is the only one I did the wet test on I realized that I wrote dry twice sorry about that the dry was 95 psi when I did the wet it went up to 145 and when I reset and redid the test it was 120. This is way my teacher stressed proofreading
 
Makes sense, oil doesn't generally help the valves seal and it doesn't last long so I'd think your guess about the rings is spot on. A leak down test couldn't hurt but I wouldn't hold your breath. Some people can't get reliable numbers on compression tests, that's why I asked about the numbers.
 
  • Like
Reactions: Davidtj
Thank you all for the answer, Not really what I wanted to hear, but what I expected. Now I have to figure out if it is worth putting the money into as I can not do the job myself I do not have the tools, the space or the skills so I will have to hire someone to do it. The jeep body is great no rust anywhere body or frame. The previous owner had a new top put on in December of 2019 I have the receipt.
 
Have you considered just replacing the rings on that piston? The other 5 look strong. Pull the head and the oil pan. Remove the rod cap. Push the piston through the top and replace the rings if the cylinder looks good then reinstall. Pretty simple job really.
 
Wild. My 4.0 has 90 in cyl 4 and 60 in cyl 5, seems down on power but no misfire codes at all. Been putting off the leak down test because I drove it that way for almost 3 years having no idea but once I know the problem I'll have to deal with it. Lol
 
Since you say the PO replaced the head recently it could be as simple as a head gasket leak. I would have that cylinder leak tested to find out.
 
Thank you all, for the advice I am going to attempt to replace all 6 pistons rings unless i need to replace the actual piston. Never done this in depth work on a motor, so a little worried.
 
Why not just find a used engine and throw it in? they are cheap and easy to find.
 
While these engines are notoriously reliable and easy to work on, 250,000 miles is still a whole lot of miles driven by other people. You said it is rust free, that makes it a worthy platform for a new engine. Rebuild or replace it, partial repairs are stalling the inevitable and throwing good money at bad. You can get a remanufactured engine with a warranty and then quit worrying for another 19 years. One shot, one kill. I know many people will tout how many miles you can get out of an inline 6, but a refreshed engine will be cheaper in the long haul and give you more confidence and pleasure.
 
  • Like
Reactions: Bud125
I don't know that replacing rings without at least a bore hone is going to help much. Maybe? Guess it depends on what the cylinder walls look like.
 
If you are going to replace rings it only makes sense to replace crank and rod bearings. And you need to pull the crank and have that worked on. And a new oil pump. With those miles you really should deck and rebuild the head. New springs and valves. And on it goes. I would take the others advice and replace the engine. Keep the old one if you want. And learn how to work on it at your leisure. Short of classes this is the best way to learn. Rebuilding and learning as you go can lead to a lot of very expensive mistakes. Take the advice of the others and put a reman engine in.
 
  • Like
Reactions: SCTexasTJ
Replacing the motor at this time is not in the cards. I simply don't have the funds for a remanufactured motor. What I have found is a cost between $1500 to $2500, plus I don't have a way to remove the motor. A hoist rental would run around 100 a week I think I would need 2 to 3 weeks, as this is something I have never done and I work two jobs and only have a few hours a day and one full day off a week.. I would have to put money aside for that. In the meantime my jeep just sits unused. Or I can fix what I know is a problem and use my jeep while I set aside money for a long term fix $3000 vs $400. to get back on the road and pretty much anywhere else. Swapping the motor is something that I have pondered, but like I said I don't have the money right now.
 
It will be easier/quicker to swap the motor than pulling the head and replacing the rings for questionable returns. Find a used motor and a local Jeep forum and ask for some help. Provide pizza and beer. Done in one day. An engine hoist only costs about $120 from HF btw.
 
  • Like
Reactions: Flivver250
Top Bottom
Back