Compressin test results

[bronzeback45]

Went to autozone and bought a tester and comfirmed that the #3 cylinder has only 70psi and the other 5 showed 110 to 115psi.

 

[wrechin2]

The knocking noise is probably a piece of the piston is broken off and banging around. Pull the head and take a look to see what you see. Post some pics.

here is some good reading on the differences of compression versus leakage
http://www.chattanoogafishingforum.com/forums/thread-view.asp?tid=50110&posts=10&start=1

 

[bronzeback45]

I pulled the head and didn't see anything and the walls look like other 2. It might be damaged on the bottom part of cylinder wall that I cant see.

 

[bronzeback45]

Here is pic of cylinder 1and the scorned #3 cylinder and a arrow shows small scatch to wall that you could see but couldn't feel.

 

[wrechin2]

Need a clearer pic of cylinder 3 like the pic of cylinder 1. Color of the piston crown looks wierd also. If you rotate the engine, does the low compression come to about the same place at the top of the cyliner as the other 2? I have see a head gasket allow water in the cylinder and bend the rod.

 

[bronzeback45]

I dropped it off at Fish N Fun Monday. The piston looked like it pushed out the same as others. I was told also it was cylinder 4. The rust color like you seen, looked like water could have entered block. The slapping/knocking could have been cause it wasnt firing on that piston.

 

[bronzeback45]

I picked up boat from fish n fun and took it to chattanooga marine. Joey said it looks like a bearing down and the cylinder walls look good to him. He is going to tear it down next week and he hopes it didn't damage the crank.

 

[stumpy]

what did the plug look like when you removed it? kinda strange for a rod bearing to cause 30-35 psi drop. you my have more than one problem, think you'll find the cylinder in question will produce a broke,stuck ring or something like that. just an observation from whats already been posted. looking forward to the diagnosis.

 

[wrechin2]

If a bearing has failed it will lower the compression by not have the correct amount of travel. That is why I asked about the movement of the piston. Sometimes it is obvious and sometimes it takes a dial indicator to compare the low cylinder to the others. A change of as little as .030 would drop compression by about 20-30 PSI depending on bore size and would be hard to tell by the naked eye. I have seen a head gasket blow and fill the cyliner up with water and lightly bend the rod and lower compression. I cut head and decks of blocks all the time. You would be surprised how a very small amount equals a large amount of volume drop. Just my .02

 

[bronzeback45]

He turned the fly wheel and the piston didn't come all the way out like others and when you pushed the piston itself it moved at least 1/4". The other pistons were tight and no slop. I was there when and seen it. That cylinder had 40psi less than all the others.

 

[wrechin2]

That is why I asked about if it looked to move as much as the others. Any update?