The first cylinder doesn't work.

[valyidol]

Hi
And again 6.5 and again problems.
1994 Tahoe. 6.5 with DB2.
The first cylinder is not working. White smoke on startup. Unburnt fuel. The engine is shaking.
After about 5 minutes, the smoke almost disappears. The engine runs smoothly. The cylinder stops working again when the engine reaches operating temperature .
The compression is great. The nozzle works great. Glow plugs works.
I removed the valve cover. There is wear on three pushrods. I changed pushrods, rockers, lifters. Nothing changed.
I removed and disassembled the head.
Here's what I saw: firstly, there is no washer under the spring of the intake valve of the first cylinder, and secondly, all exhaust valves have a very large play.
Why is the first cylinder not working? Is it because of the washer under the spring?
Or is there another reason to look for? Could it be a camshaft or IP?

 

[WarWagon]

Not enough spring tension to close the valves. Washer may increase spring tension, but, it ran before like this.

Flat lobe on camshaft: Verify rocker arm movement.

Broken valve spring under the cap. Oddly this was the highest compression cylinder when I had a broken spring. You could hear it huffing during cranking though.

Sticking valves.

Sloppy valve guides and valve can't seal all the time.

I have one engine I can "float" the valves when turning it over by hand. 4 cylinder generator engine, and yeah, the heads need to come off. It would pass a compression test, but, it would instantly die with bent valves if I attempted to start it. The engine was locked up from sitting when I first got it.

 

[dbrannon79]

are you sure fuel is getting though the one injector into the combustion chamber if you have good compression when the engine is cold. maybe a partially clogged and or stuck wide open injector. how long has it ran like this, if the cylinder is getting flooded with fuel, you would be seeing a difference in the carbon buildup when you pulled the head.

Post some photos of the head and cylinders along with other parts.

 

[valyidol]

 

[dbrannon79]

Wow that intake valve does look very loose in there. I will let other with more knowledge help with this. not sure if new valve guides will fix that or not.

the cylinder wall looks like there is a hot spot or if that is an area where the piston skirt is rubbing. does look like there is some scarring there. what was your compression numbers?

 

[WarWagon]

Both the exhaust and intake valves are loose. Service the heads with new valves and press in bronze valve guides. The valve seats may have unusual extreme wear as well.

The valve guide wear is so extreme you can see the gap in the oval hole that used to be round valve guide !!!

At some point the wear causes the valves to not seal when closed. Valve wear is known limiting item for maximum engine hours at rated power or minimum specification power level.

I would replace the rings in the cylinder and bottle brush hone it.

If you have to warranty it: rebuild it. May need oversize pistons and bored oversize. Bearings, and rebuild turbo as well as it ate the diesel thinned oil too.

This is loss of compression:
Fire goes out in the cylinder.
Then diesel fuel washes the lube oil off.
Cylinder and rings wear quickly.

I suspect one or more rings are seized in the piston.

Bearing wear may also be extreme from diesel fuel thinned engine oil. You already found severe wear in other parts of the valve train. I bet even money the camshaft is shot with a worn or flaking lobe as well.

How many miles (km) are on this engine?

 

[valyidol]

Wow that intake valve does look very loose in there. I will let other with more knowledge help with this. not sure if new valve guides will fix that or not.

the cylinder wall looks like there is a hot spot or if that is an area where the piston skirt is rubbing. does look like there is some scarring there. what was your compression numbers?

Compression test - 24

 

[valyidol]

Both the exhaust and intake valves are loose. Service the heads with new valves and press in bronze valve guides. The valve seats may have unusual extreme wear as well.

The valve guide wear is so extreme you can see the gap in the oval hole that used to be round valve guide !!!

At some point the wear causes the valves to not seal when closed. Valve wear is known limiting item for maximum engine hours at rated power or minimum specification power level.

I would replace the rings in the cylinder and bottle brush hone it.

If you have to warranty it: rebuild it. May need oversize pistons and bored oversize. Bearings, and rebuild turbo as well as it ate the diesel thinned oil too.

This is loss of compression:
Fire goes out in the cylinder.
Then diesel fuel washes the lube oil off.
Cylinder and rings wear quickly.

I suspect one or more rings are seized in the piston.

Bearing wear may also be extreme from diesel fuel thinned engine oil. You already found severe wear in other parts of the valve train. I bet even money the camshaft is shot with a worn or flaking lobe as well.

How many miles (km) are on this engine?

I don’t know how many miles are on this engine. I sow pistons 0,5 mm oversize. Today I'll try to check camshaft.

 

[dbrannon79]

24 bar, that's like 348psi for that cylinder, not too bad. I'm with WarWagon here, I think that engine has some extreme wear and mileage or hours of run time. I agree that this engine is due for an overhaul. the biggest thing to check on are main web cracks to see of it's gonna be worth the time and money to get up and going again. during your inspection be sure when you pull the pan to check for cracked main webs. tiny ones might still be usable as is, but it there are big cracks, it will need some machine shop reworking or a another engine.

what it comes down to is what your intended use is for the vehicle, how much time and money you want to put into it, and how available parts are in your area.

Were all here to help you along the way, in the end having a good dependable running truck to last many more years.

 

[valyidol]

 

[valyidol]

24 bar, that's like 348psi for that cylinder, not too bad. I'm with WarWagon here, I think that engine has some extreme wear and mileage or hours of run time. I agree that this engine is due for an overhaul. the biggest thing to check on are main web cracks to see of it's gonna be worth the time and money to get up and going again. during your inspection be sure when you pull the pan to check for cracked main webs. tiny ones might still be usable as is, but it there are big cracks, it will need some machine shop reworking or a another engine.

what it comes down to is what your intended use is for the vehicle, how much time and money you want to put into it, and how available parts are in your area.

Were all here to help you along the way, in the end having a good dependable running truck to last many more years.

Thanks

 

[dbrannon79]

from that video, it looks like there is no cracking between the valves on that cylinder. most of the 6.5 heads are known to get cracked in between the valves. if the rest look good, you may just have a good engine and heads to rebuild lasting you a lifetime. something you can pass down to your kids when that time comes.

 

[RI Chevy Silveradoman]

Just edited the thread title. I hope you fix your issue here.