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Discussion Starter #1
New to the forum, but hope someone can help answer some questions.
Have been driving the Suburban with very few problems for over 60,000 miles. Just after getting it with 149,000 miles, we replaced the PMD, have since replaced the main pulley (dampner pulley)...after knocking out the seal on the A/C compressor and the alternator bearings. New lift pump, both new batteries.

Two days ago, we had driven about 600 miles with engine running great, and pulled up to a turnpike gate when we noticed a new sound. I looked under the hood and the engine was rocking from side to side. Looked at the engine mounts, and the right side had some slack, so I thought that was the problem. Took it to the nearest dealer and had the mounts replaced. That was not the problem. Codes showing were 78 waste gate; 13 engine shutoff valve; 36 injector pulse width wide; and 92,93,94 cylinder balance. Ran test with delay off on injectors and determined that Cylinder #2 and Cylinder #7 were not firing. Checked fuel quality from filter drain, and it was good, clean (I had just serviced all filters and oil changed). We then ran compression tests and found all cylinders except #2 and #7 tested 385 psi. #2 & #7 registered no pressure. Since these are sequential cylinders in the firing order, is there something that could cause no pressure? No leakage by air test to coolant, and no loss of coolant. I was planning to remove injector #7 next, but maybe I am just wishing. Appreciate any help you can give.

Dave
 

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could be many things, i would thing blown piston but i wouldnt think both simese cylinders would be dead. could be dropped valve but that would have a really bad knock.
my best guess is pistons with gapping holes,
stupid question but you made sure glow plugs were there right?
 

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Discussion Starter #3
Glow plugs.

Glow plugs removed, connection for compression made there. Glow plugs on #2 & #7 showed some oil in addition to usual carbon. First impression was that it had to be blown piston, but sequence doesn't sound right...smooth operation with good power right up to the problem. And the firing sequence being sequential with cylinders on opposite sides and ends of the engine.
 

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hmmm oil may be pointing to blown piston, blow by? dont know what i was thinkin when i said simese cylinders, weird that at opposite ends of block.
 

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yeah, first thing to check in that the injectors and glow plugs are there and they are tight.

After that it may be time to take the drivers side valve cover off and see what condition the valve train is in.
 

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I wonder if the intake rocker arms jumped off on those two cylinders?
 

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The rocker-arm keepers are nylon buttons - they do crumble with heat and age, particularly the turbo-side, allowing the r-a's to skew.

Is very odd, 1st cyl on passenger-side, last cyl on driver's-side - could be broken r-a shaft
 

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Discussion Starter #8
Thanks for the advice. Will check today and get back.
 

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Discussion Starter #9
More Info

Checked today. Valves function OK, had cover off. While looking in where injector removed on #7, observed piston does not move when cranked...something came loose, and is probably same on #2.
 

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wow. maybe you got lucky and something gave way without destroying the entire motor. Next step is oil pan off, I would think
 

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2 clean snaps in the crank. That would be odd but if thats all thats wrong thats good.
 

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hmmm i didnt think you could see the piston with injector off, i tried lookin at mine but couldnt see through the passage
 

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Joey D;1594895; said:
2 clean snaps in the crank. That would be odd but if thats all thats wrong thats good.
umm no, how do you think the engine would work with a snapped crank?
 

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Scrufdog;1594934; said:
umm no, how do you think the engine would work with a snapped crank?
it wouldnt, apparently the rod must have snapped down low and is continuing to turn with out hitting.

has anyone else been able to see their piston with the injector out. im thinkin he just saw the combustion chamber
 

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dieselboy28;1594938; said:
it wouldnt, apparently the rod must have snapped down low and is continuing to turn with out hitting.
right. rod or cap broke. if the rod broke it was very close to the crank, otherwise it would be slapping around in there causing all kinds of noise and throwing chunks of steel into everything.
 

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my vote is for cap when piston was up top, cap mayhave fallin into oil pan, but it is all a guessing game right now.

anybody have a answer to my question?
 

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If you pull the glow plug and shine a flashlight adjusted for spot, you could see a small area of the piston at near TDC thru that half-inch port in the 'cup.

Unless maybe leaking injector had burned a hole in the crown.
 

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thanks gmctd
 

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davesmtn1, what exactely did you see, you sure you were lookin at the piston? i find it extremely unlikely that something could have let go with out making alot of ruckus and damage. especially in two cylinders at the same time.
 

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Discussion Starter #20
Considering options of repair or remove/install reman engine. The mechanic that tore down to this point was not encouraging about repair with age and miles. I find reman long blocks for about $3500. Repair of engine will probably be easier with engine pulled. Any experience out there?
 
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