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Compression Test, 48-60psi...pics

B

BotakBeng

NAXJA Forum User
Location
Las Vegas
Appreciate if i can get some info on my compression test result.

Here are some overviews on my 99 with 150k on the clock with new fully charged battery and it drives fine,
Just replaced the engine oil and it looks fine.
99XJoil1.jpg


Coolant pretty messed up (will be doing a radiator flush),
99XJcoolant1-1.jpg


Valve cover leaking (replacing soon),
99XJvalvecoverleak1.jpg


Spark plugs looks fine,
99XJsparkplugs1-1.jpg


Here is the result (cold engine),
... dry wet
#1 60 60
#2 50 70
#3 48 76
#4 51 60
#5 50 66
#6 50 74

Questions,
1)Should i do compression with cold or warm engine?
2)Avg 60psi bad?

Pls help.
Appreciate all comments.
Thx!
 
is that the coolant from the showroom floor? Man, amazing how previous owner treat their cars! Glad you are doing all this and i hope you enjoy your xj!
 
Those numbers are horrible. They should be in the 120 psi and above range. I'm surprised they didn't come up any more when done wet. Are you sure your gauge is good? With those numbers the power should be way down and might even have problems getting it to start.
 
kdub41 said:
is that the coolant from the showroom floor? Man, amazing how previous owner treat their cars! Glad you are doing all this and i hope you enjoy your xj!
Click to expand...
I loving every moment!
In fact, my favorite pass time is working on the Jeep ....beside browsing cherokee's forum :compwork:.

old_man said:
Those numbers are horrible. They should be in the 120 psi and above range. I'm surprised they didn't come up any more when done wet. Are you sure your gauge is good? With those numbers the power should be way down and might even have problems getting it to start.
Click to expand...

I'm really hoping i have a bad gauge or maybe i did something wrong.
Gonna test on my 00' Jeep tomorrow or rent another gauge from Autozone.

Did i mentioned it starts and run fine except the oil pressure is low...idling at 13 and around 47 and 3000rpm.

Anymore input?

Thx.

Btw, should i be testing it with cold or warm engine and do i need throttle at WOT?
 
Just pull all the plugs and test one cylinder at a time by cranking the starter a couple of revolutions. Make sure the gauge has an Oring so it doesn't leak.
 
old_man said:
Just pull all the plugs and test one cylinder at a time by cranking the starter a couple of revolutions. Make sure the gauge has an Oring so it doesn't leak.
Click to expand...

I have been meaning to do a compression test on my XJ, do you need to pull any fuses to prevent fuel from spraying?
 
iwannadie said:
I have been meaning to do a compression test on my XJ, do you need to pull any fuses to prevent fuel from spraying?
Click to expand...

i never do, any fuel that sprays will go right out the empty spark plug holes, or the exhaust, or maybe to meet my missing socks, who knows, it'll be fine.


as far as numbers, as has been said, waaaay low, and erratic IMHO, my old and abused renix 4.0 (with blowby) sees this:
[URL=http://imageshack.us/photo/my-images/204/10004101.jpg/]


[/URL]
 
Went over to O'reilly and rented another kit.....getting same (close) numbers.

Tested on another XJ (00'), better numbers but still in the 70's only.
I'm guessing i might have screwed up somewhere, maybe didn't screw tight enough.

Here is an update on warm engine (99'),
..... Dry ...Wet
#1.. 72...90
#2.. 78...90
#3.. 75...89
#4.. 81...92
#5.. 81...90
#6.. 90...86

Numbers looks better but still not in the 100's but numbers looks fairly even through out.

What you think?
Is she a keeper?

Thx.
 
When I did the test I stuck a screwdriver in the throttlebody linkage to keep it stuck WOT. I just pulled the fuse for the fuel pump then just turned the motor over until the pressure gauge equalized which only took like 2-3 rotations.
 
You've tried with two different gauges? And still not in the hundreds? IMO that engines as not been well maintained at all, just looking at the coolant shows. I would not count on this engine too much. Maybe swap a better one in before you put some money on this one to end up blowing it. At those rates it will be harder on gas and miss most of it's power! But to put things straight it's hard to say it might last forever or blow next week, if you are careful and do not rock it too hard it will most probably last.
 
foress_89 said:
You've tried with two different gauges? And still not in the hundreds? IMO that engines as not been well maintained at all, just looking at the coolant shows. I would not count on this engine too much. Maybe swap a better one in before you put some money on this one to end up blowing it. At those rates it will be harder on gas and miss most of it's power! But to put things straight it's hard to say it might last forever or blow next week, if you are careful and do not rock it too hard it will most probably last.
Click to expand...

That's my main concern as i have big plan for her.
I hate to bring her to the shop to have a leak-down check but if that's what i should, i probably should huh?

Btw, beside the coolant, it runs fine, no overheat, no CEL, spark plugs looks good but it does have a low oil pressure as well (idling @14psi and 3000rpm @37psi).
 
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