Problem after injector install, no comp in 7
- Thread starter Diesel Joe
- Start date
You asked “what’s the worse that could happen”, I answered that question with a very viable worse case.
You either had a piston on the verge of cracking and finally did. Injector stuck wide open and washed the cylinder wall down. Lost an injector cup or seal for the injector from not tightening the injector down well enough or a host of other things.
Don’t jump on us when you want to drive a truck and hope it fixes its self. As it’s been said before, you need to get your ass back into the truck and find out WHY you have no compression
Thats what I wanted to hear. Your saying that an injector cup or injector could cause no compession? I have tryed to figure out how that can happen. All injectors were torqued to spec, how can the injector or cup cause a leak in the combustion chamber?
If a new injector is suck wide open it could cause a burnt piston or wash out a cylider wall, correct?
When I built my motor, it idled for probably 30 seconds, then started missing out the exhaust. Something???? (never found it) had jammed in a valve and was wedging it open. Still had some compression, but a bad leak through the valve. Hit it with compressed air through the glow plug hole while spinning the engine over by hand and after a couple rotations, it blew the debris out the exhaust and sealed. Been perfect ever since.
What was the point of that story? The point is a piece of carbon, or debris from injector install, or whatever, absolutely CAN stick a valve open.
Now, at this point, I'd stop speculating as to what could have caused 0 compression and get on to actually finding out. This isn't actually too hard, especially if the valve covers are off so you know if the valves are open or not.
If the air is coming out the exhaust, it is an exhaust valve.
If the air is coming out the oil cap, you probably have a cracked piston or piston ring gone MIA. Possibly a lifted injector, but not likely.
If the air comes out the coolant tank, you have an injector cup lifted.
What was the point of that story? The point is a piece of carbon, or debris from injector install, or whatever, absolutely CAN stick a valve open.
Now, at this point, I'd stop speculating as to what could have caused 0 compression and get on to actually finding out. This isn't actually too hard, especially if the valve covers are off so you know if the valves are open or not.
- Spin the motor by hand until the problem cylinder is at TDC (more or less) with both sets of valves closed.
If the valve covers are off, verify they have 0.012" lash or more so you KNOW they are closed. - Spray compressed air in to the glow plug hole.
- Listen/feel where the air is coming out of. (Might have to remove the oil cap.)
If the air is coming out the exhaust, it is an exhaust valve.
If the air is coming out the oil cap, you probably have a cracked piston or piston ring gone MIA. Possibly a lifted injector, but not likely.
If the air comes out the coolant tank, you have an injector cup lifted.
I suppose it's possible you may have a bent or broken intake valve pushrod. If the intake valves aren't opening it can possibly give no compression on a cylinder. Do a leakdown test on number 7. Any way you look at it the valve cover has to come off.
Unless it's an egr motor there will not be any carbon build up. Time to pull it apart
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DON'T drive the truck until you figure out what happened. DON'T even start it. You'll hurt it much worse. Do you really want that expense b/c you were impatient?
Dave gave great advice to help your diagnosing. Get the valve covers back off and get started. Good luck. Hope its something simple.
Thank you Dave, what you described is exactly what mine did, your diagnostics are very helpful. This was an EGR engine, I did the delete while I was in there.I think my next move maybe to remove the exhaust manifold and have a look up the exhaust port with my camera. Not looking forward to a complete teardown!
and we have a winner!
Pulled it apart, broken pushrod on intake. Pulled the heads, with flashlight held just right I can see a faint impression of the intake valves on top of the piston. I somehow screwed up on valve adjustment!
Engine still had original crimped headgaskets, ordered new "c" gaskets and new bolts, hope that cures everything.
Anybody have a suggestion on a good machine shop in the Phoenix area for my heads?
Go down to Larry's Engine and Marine in Tucson. Larry machines all the engines i do. its a drive but he wont bull shit you and knows what those heads need to be fixed properly. Ive seen way too many shops in phx badger duramax stuff or take 5 times as long as they should on a parts.
But the question remains, WHY. I set all valves to .012, I have read where many set there's to .010. I checked the lifter thinking maybe the roller got egg shaped somehow, looks perfect. Oh well, guess at 350k it probably was time for head work and gaskets anyway. Just hope it doesnt happen again.
Same thing with mine. Freak thing. Went together perfect. But pulled apart and push rod was bent bad. Valves stamped into the piston. But no cracks and valves weren’t bent either.
Just currious which method did you use to set the valves? I always use the ICEO method. Intake closing and exhaust opening. (Set exhaust whenintake just starts to close and set intake when exhaust just starts to open) And I start with one and work my way down the bank. We did this on all our 14:1 race motors and never had an issue. Someone correct me if I'm wrong but should work on a diesel the same. I've seen some methods where they set 2 or 3 at the same time with out rotation of motor. Works for many but I never liked it. Using the ICEO method and doing one at a time you know your on the bottom of the cam lobe. Sorry to here about your motor.
Also would look at the adjusters when done and make sure the same number of threads was sticking up each. Just to see if one looked funny.
I wouldn't trust that method 100% because of possible valve overlap. If you run stock firing order, print out merchant automotive's cheat sheet in color. It tells you which valves you can set on just two revolutions. On a AF engine I use a piece of stiff wire down thru the injector bore to keep track of tdc on the compression stroke and set each cylinder one at a time.
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https://www.merchant-automotive.com/Duramax_Valve_Adjustment_Instructions.aspx#productTabs1
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