C12 Cat engine failed emissions... injector adjustments?

funkyfullwidth

New member
Hey Guys, been a long time on heavy equiptment forums and since most of my side work is bigger trucks now I jumped ship over to here! Here's my issue... Guy brought me a 2002 or so sterling tri axle. It's got a c12 cat engine and failed. As the story goes they failed inspection at around 40% opacity. Did something, not sure what and it dropped down to 34. They need to bring it down below 20%. The other complaint was that when downshifting blue smoke puffs out.. Which I have not verified. Either way, the opacity reading proves something is going on. So i'm starting simple.

As it hasn't had a service in a while i'm changing the oil and filters... The truck has 189,xxx and no service history so i'm thinking an overhead is in order. I took the valve covers and removed the 15mm hex plug on the passenger side. I turned the engine over with a breaker bar until I saw the tdc alignment hole. I verified that the valves that should be moving were, and the ones that should be closed were. All the valves were checked, the exhaust at .025 and the intake at .015. A few exhaust valves were closer to .030. Now when I went to look at the injector adjustments your supposed to adjust the injectors opposite the valves that your adjusting at the time. Well, those injectors didn't seem right. 2 were touching the arm, and the other was about an 1/8" away. should the injectors all be touching? I spun the crank around and stopped at each timing hole on the flywheel to make sure I didn't have the crank in the wrong position and either way the injectors never all seated at the same time.

I don't have alot of experience doing valve adjustments on these cats. So If someone could help spell out what's going on here i'd appreciate it. Things like, does the jake brake matter when adjusting the valves, should I adjust engine valve lash first and then injector. And what the proper way to adjust the injectors as well as is there a better way in verifying tdc besides what i've done.. Which is rotate and verify that the valves move when and where they should. Thanks guys!
 

pushbroom

Member
I don't have alot of experience doing valve adjustments on these cats. So If someone could help spell out what's going on here i'd appreciate it. Things like, does the jake brake matter when adjusting the valves, should I adjust engine valve lash first and then injector. And what the proper way to adjust the injectors as well as is there a better way in verifying tdc besides what i've done.. Which is rotate and verify that the valves move when and where they should. Thanks guys!
Always adjust valves first, then adjust the intake actuators or jakes. Jakes ride on top of the valve adjustment so the valves must be adjusted first. Doesnt matter when you adjust injectors, they are seperate from the valves. Tdc is just the pin hole in the flywheel. A 3/8 bolt works good as a pin. I rarely work on the C12s so if i could get your engine serial number I could give you specs on the injector adjustments.
 

ask4more

Banned
I'm not sure if it can help you, i've seen this manual a few days ago,
 
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