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04-21-2007, 09:35 AM
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#1 |
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Blue 67
 Join Date: Apr 2004
Location: Western WA
Posts: 1,178
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compression testing
When you do compression test, do you remove all the spark plugs at once or one at time when you are testing each cylinder? Does the cylinder has to be on TDC? I got kind of confused about compression test and leak down test. would somebod explain this to me.
Thanks a lot.
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1953 GMC 3/4 ton: current project 1967 C20: 5.3 voretc with T5 conversion, 4 wheel 8 lug disc brake 1972 Nova: my 4 door sport sedan! 5.3 voretc + T5 conversion. drivable project, FUN!! 1979 Camaro Z28: 5.3 vortec conversion with build TH350: drivable project, Fun to drive 1992 Camaro RS convertible (Z28 clone): 5.3 conversion with build T5: on going project 2005 Silverado 2500, 4x4 Duramax, original owner |
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04-21-2007, 10:48 AM
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#2 |
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Registered User
Join Date: Feb 2007
Location: Lexington Park, MD
Posts: 47
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Re: compression testing
Im pretty sure you just have to take one spark plug out, disconnect the ignition system and screw the hose onto the spark plug hole with the gauge. then have someone turn the key at WOT. let them hold the key over until the gauge stops increasing. Ill tell you about a good or bad compression test if you need me to. But thats how you set it up, I think. Make sure you let the starter cool down and to make sure there is no gas in your testing hose, or it will give you a bad reading.---Andy
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1972 Chevy Truck 350ci/th350 Auto. Daily Driver 
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04-21-2007, 11:44 AM
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#3 |
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Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: compression testing
i take all out its easier to spin the motor that way
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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04-21-2007, 12:18 PM
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#4 |
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Registered User
Join Date: Nov 2005
Location: Atlanta, GA
Posts: 40
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Re: compression testing
all spark plugs out, hold throttle wide open, spin engine for about 4-5 secs.
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04-21-2007, 04:04 PM
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#5 |
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Blue 67
Join Date: Apr 2004
Location: Western WA
Posts: 1,178
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Re: compression testing
If I take all the spark plugs out, do I need to disconnect the ignition still?
__________________
1953 GMC 3/4 ton: current project 1967 C20: 5.3 voretc with T5 conversion, 4 wheel 8 lug disc brake 1972 Nova: my 4 door sport sedan! 5.3 voretc + T5 conversion. drivable project, FUN!! 1979 Camaro Z28: 5.3 vortec conversion with build TH350: drivable project, Fun to drive 1992 Camaro RS convertible (Z28 clone): 5.3 conversion with build T5: on going project 2005 Silverado 2500, 4x4 Duramax, original owner |
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04-21-2007, 04:38 PM
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#6 |
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Registered User
Join Date: Feb 2002
Location: Vacaville, CA
Posts: 2,746
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Re: compression testing
No, just stay away from the wires with your hands though.
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 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI |
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04-21-2007, 05:02 PM
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#7 |
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Resident Absorber
Join Date: Mar 2007
Location: WI
Posts: 131
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Re: compression testing
you want to do it while the engine is warm also.. ex: engine at op temp, then pull all plugs and comp test. after testing all cylinders dry, test each one again after a small squirt of oil. If compression gets significantly better after the squirt of oil, that indicates bad rings or scored cylinder walls.
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