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[DeezilDoc]

I have a 1995 GMC 1 ton with a 6.5,trouble started with stalling,and after talking to the pump builder removed the injection pump for rebuild. when I tried to re-install pump found engine would not turn completely over (only turns about 330 degrees before locking up) can turn back in the other direction but locks up again. My question is how could anything get on top of piston or in cylinder area past the valves if in fact this is what's happening, I stuffed rags in the ex and intake ports to prevent anything from getting into the heads. would appreciate any advice before I remove cyl heads. Thanx

[gmctd]

Try removing all the injectors or all the glow plugs - or split'em by cylinder, whichever is easiest - give it a whirl - that will eliminate possible hydrolock - removing the injectors will let you see general gp condition

Btw - welcome to the 'Page, on your first post since April..................

[DeezilDoc]

pulled all glow plugs,removed water pump and drive gear for injection pump.....found nothing yet

[gmctd]

Crank still won't rotate 360deg?

[DeezilDoc]

no,still the same. guess my next step is to remove valve covers and see if I can find which cylinder is locking up

[gmctd]

Yep - look for a dropped valve

[twaddle]

Before you start taking too many things apart, get a snake magnet and probe into the intake ports just in case a washer or something has got into a port and lodged in the valve seat holding the valve open a little.
You may need to turn the engine over a little to prevent the valve holding onto whatever is in there.

You may also have to remove the rocker arms assemblies to see if any valves are sitting lower than the others.

Good luck

Jim
Biggar Scotland
Soon to be Alberta, Canada

[Robyn]

I have seen large carbon deposits around valves get dislodged during maintenance and fall into the cylinder and cause what you are seeing.
Does the engine come up hard like a metal object or more soft like what I am speaking of.

There is very little room between the head and the piston crown in these engines so any little thing will cause issue.

Unless you can absolutely be sure of what it is and fish it out the heads are probably going to have to come off.

If anything hard gets in there it will result in a 5 alarm train wreck inside the engine.

Good luck and keep us posted

Robyn

[DeezilDoc]

CARBON it is..........checked intake ports with a magnet,found nothing,took the air hose and blew 150 psi air into intakes chunks of carbon came flying out. It's still a little hard to turn over @ certain points but does go completely around.Gonna put it back together,start it up and blow the carbon out the exhaust. thank you to ALL who replied

[DmaxMaverick]

CARBON it is..........checked intake ports with a magnet,found nothing,took the air hose and blew 150 psi air into intakes chunks of carbon came flying out. It's still a little hard to turn over @ certain points but does go completely around.Gonna put it back together,start it up and blow the carbon out the exhaust. thank you to ALL who replied


If you must, but........

I do not recommend starting that engine until it turns freely, all the way around, many times, repeatedly. If there is something in there hindering rotation, you will likely find out what a real seized engine is like. Soot/carbon is very abrasive. If you have chunks in the cylinders, not only can it interfere with piston/valve clearance, it can also score the cylinders. All Diesel engines get soot buildup, but it, for the most part, stays where it belongs, or works out gradually as it runs. At any rate, I woudn't be too convinced it was soot that was halting your rotation. The stuff in the intake is very normal, and especially so in C (6.2) or S (6.5) engines, due to the EGR. What you blew out may have just been normal buildup, and the engine freeing up (however slight), was just a coincidence. Also, if you have a turbo, would you really want all those "rocks" going through the turbine? Not me!

[DeezilDoc]

Im satisfied it is carbon........the engine ran fine and turned over freely when removing the inj pump, I took the precautions of stuffing rags in cyl heads before removing the pump,it turned over freely while removing pump. Problem was when I tried to reinstall pump, will turn it over a few more times and keep blowing out cylinders with air before installing glow plugs

[DeezilDoc]

Finally got it running.............