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Discussion Starter · #1 ·
Need help motor turns over but half way through the rotation it locks up it will rotate backwards till it locks up again
 

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Need help motor turns over but half way through the rotation it locks up it will rotate backwards till it locks up again
Welcome to DieselPlace
Please tell us a little more about the vehicle ( Year, Make, and Model ) and list any mods.
(y)
 

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03 Sierra 2500 HD 6.6 Duramax an from what old owner told me studded deleted an I’m not sure of anything else really
 

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03 Sierra 2500 HD 6.6 Duramax an from what old owner told me studded deleted an I’m not sure of anything else really
Have you removed the glow plugs and tried to crank the engine over or tried to bar the engine over by hand?
 

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Yes I did an I marked the crank with a line an on the block an it’s almost a full rotation it’s got about 4 inches before it’s completely turned over
 

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It was Runnin great then all of a sudden it smoked alil bit then stalled an I started it again ran for 30 secs then died it didn’t make no noise or anything oil was perfect with no metal in it An anti Freeze was also good I marked the crank an the block an it turns completely over till about 3 inch from a complete rotation
 

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It was Runnin great then all of a sudden it smoked alil bit then stalled an I started it again ran for 30 secs then died it didn’t make no noise or anything oil was perfect with no metal in it An anti Freeze was also good I marked the crank an the block an it turns completely over till about 3 inch from a complete rotation
If you removed the glows and attempted to turn it over then your next step would be to pull the valve covers and start inspecting
 

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I’m a diesel mechanic by trade, my smallest scope is 5.5mm still too big to go through a glow plug hole. If you pulled the glow plugs and still won’t bar over, that eliminates hydro lock either fuel or coolant, that leaves mechanical interference, ie a valve or maybe a rocker bridge jumped if a valve stuck in the guide. The minimum ,the heads are probably coming off would be the next step. If you pull the valve covers your not far from pulling the injectors and running a scope through those. 4” of rotation is about 30 degrees, could be something passed by the intake valve, was there any work done that had the intake bridge apart. If you find what it is you might pull the exhaust manifold and fish it out by rotating the exhaust valve open.
 

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Discussion Starter · #12 ·
I’m a diesel mechanic by trade, my smallest scope is 5.5mm still too big to go through a glow plug hole. If you pulled the glow plugs and still won’t bar over, that eliminates hydro lock either fuel or coolant, that leaves mechanical interference, ie a valve or maybe a rocker bridge jumped if a valve stuck in the guide. The minimum ,the heads are probably coming off would be the next step. If you pull the valve covers your not far from pulling the injectors and running a scope through those. 4” of rotation is about 30 degrees, could be something passed by the intake valve, was there any work done that had the intake bridge apart. If you find what it is you might pull the exhaust manifold and fish it out by rotating the exhaust valve open.
There was no work or anything taking off that I know of but it’s been a great truck while I had it up until this point
 

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So Snap-On offers a 3.8mm option for the borescopes here is a picture of part number of 3.8mm & what models it fits.
Sorry for bad pic, trying to get out the door for work.
 

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