Low compression, possible anything easy?

[dieselrealtor]

Continued from a previous post http://www.thedieselpageforums.com/tdpforum/showthread.php?goto=newpost&t=23774

Decided to do a compression test before further troubleshooting of the fuel system.

About 140psi of compression in the 5 cylinders I checked, I didn't see the need to check the other 3. The strange thing is there is really no blowby coming from the oil fill tube when cranking.

What I know; (I just bought it not running, 2nd hand information)

died while driving, would not restart.
took to a dealer & after some checkout they asked him if he was running a chip or programmer, he said yes. They told him the engine is toast & would at the very least need pistons.

I am not optomistic, but is there anything cheap or easy (compared to pulling engine) that could cause this?

Is there any possiblity that bad injectors (warranty) could have caused this?

If not, I am looking to buy a used engine to swap out if I can find one in the next week or so, if not I will be pulling this one to rebuild.

[Kennedy]

Are you sure that your compression tester is accurate?

[dieselrealtor]

Are you sure that your compression tester is accurate?


Yes, (close enough) I went out to check this morning against my compressor, it is within 10psi of the compressor gauge.

[Kennedy]

I guess you should be looking for bent pushrods next. Sheared cam pin, bent pushrods, or bent con rods would be most likely culprits.

[dieselrealtor]

Is this something that can be done in the truck or is it easier to just pull it?

Where is the best place to buy a factory shop manual or equivelant?

Thanks J.K.

[dieselrealtor]

I bit the bullet & took it off the trailer & put it in the garage.

Compression results;

(assuming driver side front is #1, back & forth to #8 passenger side rear).

#1 170
#2 180
#3 120
#4 220
#5 140
#6 180
#7 140
#8 110

I noticed when I started they were lower than the other day & the batteries seemed weak, I put the charger on for an hour before I started.

Valve timing does sound plausable, if no other suggestions, I will start taking the front of the engine down in the next couple of days.

[Kennedy]

Try a leakdown test maybe???

[dieselrealtor]

I have never done one, they were coming out with those after I quit wrenching but before I got out of management so I am vaguely familiar with them, maybe another toy for my box :-).

If I get one I will definitely have to read the instructions.

How far do you have to go into the top end to get to the push rods to do a visual?

[dmaxalliTech]

How do the glow plugs look?

Does it turn over "smooth" as in no sudden hick ups or drops in rpm when cranking like its hitting a dead spot? Can you hear air "hissing" out the glow plug holes when cranking it?

There is not a specific value that we are looking for per sea, but rather with in a certain range. We like to see compression with in 15% across the board.

I am with the others in my thoughts, Being that we dont know a good history on the truck, its hard to form any thoughts on a way to proceed with out testing. You may choose to replace the motor in it depending on your findings. There is a spot here in MI that sells alot of GM stuff called Schram.

My thoughts based on your compression tests indicate a problem across the board rather then an individual cylinder problem. Its possible that all the rods are bent, but not very likely. A sheared cam pin is possible, but that would really put compression numbers down as with the valves not opening and closing, there would be no air to build pressures. Bent pushrods have to come from something and a sheared cam pin will bend all the exhaust pushrods nearly every time and depending on when it goes, will allow you to see through the block very clearly.

Is there fuel spray coming out of the glow plug holes when cranking or do you have the fuel system disabled? If it is disabled, do you have fuel from it?

Lots of questions in my head...awaiting your findings

[dieselrealtor]

The glow plugs are somewhat burnt on the ends, I don't know how much is gone & how much is normal.

It turns over smooth (all the glow plugs are out) & there is air & fuel that is spraying from the holes.

How far do I need to go into it to see the push rods?

I don't have a radiator pressure tester, I may buy one.

Are these symptoms of a diesel that has "hydraulic'd".
This is similar to what I saw when someone drove a Mitsu 3000 into water.

The oil looks a little cleaner (& no milk or water) than it does on my 6.5, maybe just over the full mark, has been under 3000 miles since last change, the drain plug/pan has a painted mark across that indicates to me that the oil hasn't been changed recently.

I have called the previous owner to find out what, exactly, happened but he is far too important & busy to spare me 90 seconds on the phone :-(.

I have found some complete engines locally ranging from $3500-$4200 + ($500 core, I would keep it for that), I would rather avoid this expense if possible.

[Kennedy]

At this point, my best suggestion would be to pull the engine and get it on a stand so you can start disassembling and inspecting rather than standing on your head in chassis.

[dieselrealtor]

Do you know of any engine parts (rings, etc) available in the aftermarket?
I have priced parts to rebuild at the dealer, WOW. $90 for rings, PER PISTON!

[Kennedy]

Pistons and rings no problem.

[dieselrealtor]

I found this used engine, sounds like what very well may have happened to mine?

the cam is not seized, all push rods are bent.

[BILLYDIESEL]

I'v Come Across Many 6.6 Valves Seizing Up In Head Due To Lack Of
Oil.send Head Out For Rebuild Or Free Up Avlve Guides Will Be O.k.

[dieselrealtor]

Pulled the head tonight off the pass. side, the valves are a little leaky but the least of my problems.

The cylinders are about 4.053", about .002" egg shape. #7 severely scored.
The pistons seem too "small", there is about a 1/8" gap between the piston & the cylinder wall.

Pics

http://www.thedieselpageforums.com/photopost/showgallery.php?cat=500&ppuser=11622

[JohnC]

WOW!

I need new glasses, but it sure looks like the pistons have been grabbing the cylinders. Musta been some serious heat in there...

[dieselrealtor]

The head is only warped about .001", this is from the outside to outside, between the cylinders is flat. The surface of the head does not resemble the tops of the pistons, however the valves & seats are pitted. I don't think the seats sank into the head, the tops of the valves are of identical height.

I did find a small flake of piston stuck to an intake valve in #7.

#7 is the worst on the side that the head is off, but the other 3 pistons have aluminum "gone".

What are the odds that the block is;
cracked?
boreable?
honeable?

At this point I am looking for a good used engine but am pricing parts to rebuild this one so I can compare.

Suggestions???????

[Mark Rinker]

http://cgi.ebay.com/ebaymotors/DURAMAX-TURBO-DIESEL-6-6-ENGINE-HUMMER-H1-H2-LB7-01-02_W0QQcmdZViewItemQQcategoryZ33615QQihZ019QQitemZ 8058707305QQrdZ1QQsspagenameZWD1V

[dieselrealtor]

Mark, what are you trying to tell me?


Hey all, is it possible that a complete LBZ with engine, trans & transfer as well as computers could be a "plug & play"?

Are the wiring harnesses to the truck similar or even identical?

[SoTxPollock]

Since your going to start at the front of the engine, I'd check the cam gear to be sure someone didn't install the cam in the wrong position, like a tooth off, that would cause the valve events to be off just enough to not get or keep all the air in the cylinders the proper time. Its very unusual to have all cylinders off spec that much on the pressure, but your # 4 is 220??, even thats a hundred low. Maybe those guys ran it so hard they melted the tops of the pistons off and gaulded the cylinder walls. I can't imagine one being that badly worn out, unless they never changed the oil at all.

Of course if it was mine, I'd have it on the engine stand and carefully disassemble every part on it to be sure of what I had to work with.
Best of luck to you Bud, I think your gonna need it on this one.

[dmaxalliTech]

Looks like it had some issues.

I may be able to help round up spare parts but I think at this point and by looking at the pics, your further ahead getting a used engine