07.5 6.7 3500 DRW 4x4 manual, smarty on 1, no emissions studded, pyro, boost and fuel pressure guages.

Driving down the road empty at 75, thougth the truck sounded funny but the road was pretty rough, all the guages were normal. Coming to the intersection something was wrong, just sounded funny. Pulled over, truck had a miss. Looked under the hood for obvious problems, leaks, loose boots, nothing found. truck was shaking, maybe rocking back and forth if you will. Could hear a dead cylinder, or miss of some sort. Rev the motor up, at about 2,000 rpms, felt like the miss was gone, or at least better- so I figured ok bad injector for sure. I was in the middle of nowwhere literally, so I figured i better start limping it for the next sizable town (Ely, Nevada.) Took off nice and easy, got into 6th, at 55 or so, truck began to make serious engine noise, so much so that it spooked me a little bit. Clutched it immediatly, gave the pyro a second look, about 500-600, waited 3 seconds for egt to come down and shut it off.

Hooked up the smarty to check for codes, nothing except for a turbocharger code, no injector codes or anything.

So get the tow truck ride to the dealer, dealer checks for bad injector(s). Finds none. I watched him shut them off one by one, the knock got much better, but never went away. So he says the motor is junk, and has a rotating assembly problem in the bottom end some where. And its $15k-20K to fix. (Long block plus labor). So where do I start? Oil is perfect, nothing obviously wrong besides serious engine noise. Any ideas? Totally frustrated, and stuck in Ely Nevada

 

Get second opinion, I've had injector go bad and you would think the engine was junk, hammering and knocking, I would locate cylinder that is causing knock, pull injector look for any damage on tip. Use bore scope inspect cylinder. Perform compression test on that cylinder. Swap injector to another cylinder does knock move to that cylinder? Replace injector then, also 6.7 injectors have code to program to ECM when replacing. Good indication that you have internal engine damage, remove oil cap and start engine, any blowby gases coming out? If piston is damaged you will have excessive blowby out oil fill.

 

You need to do more trouble shooting,if oil press stayed the same it's unlikely crank bearings are shot,can you cut oil filter open.?i think you may have to tow it to a better shop if possible,way more things to check before they can say block is no good

 

Haven't gotten around to checking anything besides the injectors really. I did check the oil twice, and so did the mechanics. Its perfect. It was just changed about 750 miles ago, so its perfect gold colored yet, with nothing shiney in it. Looking at getting the truck hauled back to Idaho where we are living and deal with it there. Unless the bearing spun in the block (which I don't even know if they can) I don't see why the block would be bad? I could see a rod bearing, or even a spun crank bearing, but not the need for a complete long block.

I would like somebody to prove that its not injectors, or anything else. The noise got a lot better when he was playing with the injectors... If the truck is not showing a code, does that rule out a bad injector?

Is there anyway to prove rotating assembly failure without pulling the motor, and droping the pan? We see bad bearings at work all the time, but we have a vibration analysis team that is constantly monitoring and checking all of our pumps, bearings, motors, etc...

 

An oil analysis will show you if there's anything going on inside. Elevated amounts of wear metals will point you in the right direction. $15K-$20K sounds awful high. You've gotten good advice so far. A flow return check wouldn't hurt either. Some guys like to check compression hot and cold too.

 

with the engine missing i do not believe you have a rotating problem. remove the valve cover and start or spin the engine and observe the tappets, if you have a valve seat problem you should spot the bad cylinder. also i have used a laser heat gun to spot the dead cylinder, just start the engine and keep checking each exhaust port, one will be lower than the others. while you have the cover off check the resistance of each injector. it should be about 0.5 ohms if a crystal cracks the resistance go's up, in about 10 ohm range it will cause funny problems but usually throws you in limp mode. above 1 ohm it is bad. the 7.5 still did not have good fuel filtering, the 10 micron stock filter would let enough 5 to 7 micron dirt through to bind the tight tolerance tip that it would either cause the crystal to crack or bind the injector closed or open. if it binds open it would have been obvious, the mpg goes to gpm and no one behind you can see you for the black smoke. i know from experience. if it sticks shut also from experience it will not throw a code and the cylinder will miss. in trying to give you things to check there in Ely with out proper tools i would find the cylinder not firing by the above test's and if no visible problem found, swap the injector with another hole to see if the problem moves. once you get the problem fixed pm me and will give how to for better filtering.