no compression

[nissanprerunnerdavid]

So figured out its not a Carb problem. I dont have any compression. I plug a air hose into the plug hole and the air just blows by. The valves are closed and still air somehow gets by?? I rebuilt the engine lime 2 weeks ago so I don't know what could have gone wrong? Maybe rings or what??

[wayno]

So figured out its not a Carb problem. I dont have any compression. I plug a air hose into the plug hole and the air just blows by. The valves are closed and still air somehow gets by?? I rebuilt the engine lime 2 weeks ago so I don't know what could have gone wrong? Maybe rings or what??

 

 

Has it ever ran since the rebuild?

[metalmonkey47]

Valves adjusted too tight? Maybe they look like they're closed, but the air is leaking past the valve seat?

[Sealik]

Where is the air going....out the carb, exhaust or crank case?

[metalmonkey47]

Where is the air going....out the carb, exhaust or crank case?

 

Damn, that's a good one.

 

Crankcase=rings

Exhaust=Exhaust valves

Carb=Intake valves.

[TENDRIL]

are you using a compression tester or just an air hose that runs off of an air tank?

[nissanprerunnerdavid]

I used both and what I sadly found is that my cylinder walls were scored bad. Yes it rank for about 2 weeks since the rebuild. The air was going to the crankcase because nothing was leaking. My diagnosis is that the Carb was burning waaaaay to rich and therefore washed my cylinder walls out then while I as driving as soon as I let off the gas there was not enough compression to keep it running. I have never hear of that happening after 2 weeks of running though?? I aM going to pull the motor AGAIN...

[nissanprerunnerdavid]

I used an inspection scope camera to see the cylinder walls.

[banzai510(hainz)]

you gap the rings??????????

 

scorne cylinder walls would be alot of crank case blowby at idle.

 

valve adjusted correctly?????????

[nissanprerunnerdavid]

Yeah they were capped along with the valves.

[datzenmike]

Did you look at the top edges of the piston? Could be the ring land has broken away. Too advanced timing could lead to detonation. This would break away the piston top.

 

Did you measure the cylinder walls and compare to the piston? Or just hone it and go with new rings? Piston to bore clearance should be 0.001 to 0.002" or 1 to 2 thou. If the cylinder is worn out, new rings will be extended out from the ring groove too far to seal.

[nissanprerunnerdavid]

So I finally got time today to pull and completely dismember my engine. I had about 15-20 psi of compression when I pulled it so that is no good. I turn the engine over by hand by the crank pulley bolt, could turn it over with one finger!!!! It was soooooo easy. So that leaders me to be live that it has so.etching to do with the rings because the walls of the cylinder were almost untouched but the rngs werets sealingcorrectly. That is what i concur. It may be that I just got the block honed instead of bored and went with standard pistons. Any other culprits would be awesome to consider. I'm gonna finish up this week and send it away to be bore to .20 over and get over size pistons and rings......damn trucks..... :)

[nissanprerunnerdavid]

Sorry. Swype is killing me...

[nissanprerunnerdavid]

anydody know a place to get decent quality american made pistons and rings that wont shred my bank account??