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  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
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Compression Test

  • Thread starter Thread starter UTGAMER
  • Start date Start date Jul 26, 2010

UTGAMER

New Member
Feb 26, 2010
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Dalton, GA
Jul 26, 2010
#1
  • Jul 26, 2010
  • #1
So I finally get around to doing the test and it starts raining.


I was needing to ask yall what should the psi gauge read? I only got to check 1 cylinder and its was maybe 65, but the ignition coil was still hooked up and engine was cold. I cant get car to run to warm it up
 

UTGAMER

New Member
Feb 26, 2010
215
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0
Dalton, GA
Jul 26, 2010
#2
  • Jul 26, 2010
  • #2
Also it says if it compression goes up after adding oil it is worn pistons, but if it stays the same that its leakage in valves, so this confuses me. Should it stay the same, drop or rise? lol
 
B

bayellowstang

Member
Apr 25, 2003
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Carlisle, PA
Jul 26, 2010
#3
  • Jul 26, 2010
  • #3
I don't know about the rest of the stuff but normally they should be around 180 or so.
 

UTGAMER

New Member
Feb 26, 2010
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Dalton, GA
Jul 26, 2010
#4
  • Jul 26, 2010
  • #4
Well it quit raining for a min and the next 2 were 125
 

Chythar

Recently finished repairing my rear
20+ Year Stangneter
Aug 26, 2004
2,373
140
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Foothill Ranch, CA
Jul 26, 2010
#5
  • Jul 26, 2010
  • #5
I've read folks here report anywhere between 120 and 150 and still be "OK". The main thing you're looking for is one cylinder with a significantly lower number than the rest. That tells you which cylinder has worn rings. We're talking more then 5-10 psi difference. The higher the overall numbers, the better.

As I remember, adding oil should either give you higher compression numbers or no change. If you get noticeably higher numbers, you're getting air & fuel pushing past the piston. In this case it usually means worn rings but can be other damage. No change with low psi can be valve seals but can be a damaged piston too. You'll need to complete the compression test before we can give you any definite ideas.
 

UTGAMER

New Member
Feb 26, 2010
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0
Dalton, GA
Jul 26, 2010
#6
  • Jul 26, 2010
  • #6
I know was just bumed it was a 65-75 then happy it was 125. And it was raining so I though Id update. Now I just read that your supposed to only remove 1 spark plug at a time?
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
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Jul 26, 2010
#7
  • Jul 26, 2010
  • #7
It's best to have a hot motor. You can pull all the plugs at once. Connect a battery charger for equal cranking as you go. Disable the ignition and/or fuel system. Prop the throttle wide open. Then do the testing.

Did you ever do a cylinder-balance test while pulling codes? If one cylinder was not contributing properly, the test would have revealed it. It also makes it easier to pinpoint which cylinder(s) need attention.
 
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