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Old 08-29-2007, 05:18 PM
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piston ring?

truck is a '97 7.3 PSD the symptoms were low compression in cylinder 6 and ran aweful. during my drivers side head removal process I came accross a bent glow plug in the number 6 cylinder. I get the head off expecting the worst. but much to my surprise I did not find a hole lot. I did not drain the oil and fuel before pulling the injectors. so of course all three rear pistons were in the down position and each one was holding about the same amount of oil. I extract the oil from the cylinders and start investigating, the number six cylinder is very,very slightly scored on the outside most part of the cylinder, and at the top of the cylinder there is a black hard residue the extends down past the normal residue ring. I am assuming this is a bad ring. now i am wondering if I could hone out this cylinder wall and put a slightly oversized ring in it?? I would assume also that from the bent glow plug there should have been foreign debri but there was none to be founf and the head is in excelent shaep. oh the top of the piston was clean right near the scratch in the cylinder wall.
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Old 08-29-2007, 05:40 PM
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I have some questions. How did you arrive at low compression, did you do a compression test? Is the engine still in the Truck and you just pulled the head? (what stage of tear down are you in) I'm just trying to get an overall
idea of the situation. How deep are the cylinder scores?

Jim
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Old 08-29-2007, 05:43 PM
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One other question, how many miles are on the engine?

Jim
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Old 08-29-2007, 10:05 PM
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I picked the truck up from my dad in New Mexico for free. he had a mechanic look at it, with out tearing the head off. he performed a compression test and cylinder contribution test. replaced the number 6 injector. The truck and engine have 175000 miles on it. I have the head tore off and motor is still in truck. the scores in the cylinder wall are shallow enought that your fingernail wont get hung up on them they are smoother and rounded edges wich tells me that it has been scored for a while, I think that the ring is stuck and I just need a few more opinions before I go tearing the oil pan off and pulling the piston and rod.

I wish I had not messed up the head gasket during tear down because the head rested on it on the number 6 cyl hole of the head gasket. it could have possibly been a blown head gasket but I dont think i am that lucky. I was also thinking valve but they look good.
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Old 08-30-2007, 06:26 PM
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Was the truck stored for any length of time? because the injector orings can go bad sometimes. I'm going out of town tomorrow and maybe some of the others wil chime in and give some advise. I hope you get things going your way.

Jim
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Old 08-30-2007, 06:39 PM
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I'm not sure what the tolerances are on the stock rings, but you should measure the bore at several different places to check for taper and wear, before you will know if you can hone the cylinder.
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