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Odd Compression Test Results

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Odd Compression Test Results

 
Old 02-20-2019, 04:35 AM
  #21  
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Originally Posted by Billman250 View Post
The classic #4 cylinder liner failure will result in high compression in number 4.

Check the cylinder with a scope, with piston at BDC. Liner failure will look like a wide black stripe.

Do not pull the full pump fuse for a compression test. Fuel will still spray into the cylinders and skew the readings. It is also unhealthy for the engine.

Disconnect the injectors instead.
I will do a little searching, but do you have more info on this cylinder 4 liner failing?
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Old 02-20-2019, 05:03 AM
  #22  
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Just bore scope it, it is easy to spot.
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Old 02-20-2019, 05:06 AM
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Originally Posted by fatjoe10 View Post
What's the mechanical/scientific reason behind having high compression with damage to the liner? interesting.
Liner damage allows excess oil to flood the compression rings, raising the compression.
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Old 02-20-2019, 05:54 AM
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Originally Posted by treimche View Post
Let me explain a little better. With the leak down tester in cylinder 1, I can hear air escaping through cylinder 2 and 3 spark plug holes. It wasn't leaking through the spark plug hole where the tester was.
Thanks that makes perfect sense.
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Old 02-20-2019, 06:18 AM
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Originally Posted by Billman250 View Post


Liner damage allows excess oil to flood the compression rings, raising the compression.
That makes sense. Any idea what causes this to happen? Something ring related that scores the cylinder liner?
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Old 02-20-2019, 07:48 AM
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40% leakdown? what the **** lol. my 220k motor has 6-8% across all 4 and all read 210psi with 5 cranks.

Something sounds wrong lol.
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Old 02-20-2019, 08:42 AM
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Originally Posted by Deckoz View Post
40% leakdown? what the **** lol. my 220k motor has 6-8% across all 4 and all read 210psi with 5 cranks.

Something sounds wrong lol.
Yeah tell me about it. This really sucks. This is the pic I took of the gauges when checking cylinder #2. Maybe I did the math wrong.

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Old 02-20-2019, 12:07 PM
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Do I understand correctly that the engine runs fine?
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Old 02-20-2019, 12:44 PM
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Your results seem pretty high for an engine that actually runs. I notice you didn't have the cylinder head cover off during the leakdown test. How did you confirm each cylinder was at TDC during the test? Perhaps you had some valves that were not completely closed?
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Old 02-20-2019, 05:44 PM
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Originally Posted by rpg51 View Post
Do I understand correctly that the engine runs fine?
Yeah it runs just fine.
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