Loud knock, black smoke

[CaptPhil]

Driving my stock truck yesterday, gave it a little half throttle pull from 65-90mph, literally half throttle, fifth gear. Slowed back down to normal and it started knocking bad on one cylinder. Drove it home sounding like a tractor, fortunately was only about three miles. It accelerates fine. Truck shakes bad at idle, hazes black with any throttle input. Starts right up.

Balance rates all show zero, no injector codes. Using DVTs I shut of each injector, on number six the truck gets quiet immediately at idle but will start knocking again over 1000rpm. Swapped five and six to see if it was the injector hanging with no change.

Didn't think about how the lly dvts are labelled wrong, so now thinking that it might be injector three that I am shutting off.

At this point I am thinking valve train issue or hanging injector. No blowby at all, balancer is rock solid.

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[gmac32]

Definitely an injector. Had several like that on my old lly

 

[hondarider552]

I almost killed my single cab LBZ when the injector stuck open.

 

[Schwinn68]

Lly correct? Did you do the ice pick trick? Do a search on the explanation but my truck has done that to me. Once I used the ice pick on the connector it hasn't acted up since.

 

[Harbin_22]

Unplugged the injectors, pull glow plugs and look for fuel coming out of that cylinder if you think it is hung.

 

[CaptPhil]

Lly correct? Did you do the ice pick trick? Do a search on the explanation but my truck has done that to me. Once I used the ice pick on the connector it hasn't acted up since.

I have, but most of the time you lose an entire bank when that happens, and it throws injector open circuit codes. I am getting no codes.

Just swapped injector three and six, no change. So either the efilive dvts are mislabeled or it is a hard part problem.

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[Harbin_22]

Might try maxing rail while watching balance rates too. I had one that was ok at idle pressure but once I upped rail, rates would go through the roof.

 

[CaptPhil]

Might try maxing rail while watching balance rates too. I had one that was ok at idle pressure but once I upped rail, rates would go through the roof.

Not giving me balance rates.

This thing is knocking like it is coming apart until I shut off one injector. Would I be able to shut off a hung injector?

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[baggedLB7]

Unplugged the injectors, pull glow plugs and look for fuel coming out of that cylinder if you think it is hung.

Do this its easy to do. Have someone turn it over while you watch if you have one hunge or leaking it will spray a misty cloud out the injector hole.

 

[henery97]

I know for a fact that the lbz dvt controls are labeled incorrectly. I would assume the lly DVTs are the same

 

[onebaddmaxxx]

Just come get my tech2 :hug:

 

[CaptPhil]

Do this its easy to do. Have someone turn it over while you watch if you have one hunge or leaking it will spray a misty cloud out the injector hole.

Did this after I swapped injector 8 and 5 (because 5 is easiest to get to). Used a stethoscope on eight and could hear it hammering.

Truck almost started after that then would turn over fast then hit a wall, which I am guessing was a partial hydro lock. Pulled the glow plug out of five and it is straight dumping fuel out, won't build enough rail pressure to start. With the glow plug out the motor turns over smooth on the starter.

So looks like I need an injector.

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[DURAMAXD219]

This sounds way to familiar. My regular cab LLY does that same thing. I'm convinced mine is a fuel knock. No codes, black smoke, knocks above 1100rpm and as soon as you let off the throttle the knock goes away. Some days are worse then others. I'm interested to see if a new injector(s) fix your problem.

 

[NC-smokinlmm]

Make double sure your harness at the ficm and alternator isnt chaffed.

 

[CaptPhil]

Couldn't get an injector locally, so called LDS and had them overnight one yesterday, got here today at 2:30, test drive done by 4:00. Balance rates are perfect and everything is back to normal.

Turns out that on the efilive dvts, injector six is actually injector eight. Wish it had been right, would have saved me hours of trouble swapping injectors around.

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[DURAMAXD219]

So one injector fixed your issue. Gives me hope for mine.

 

[kiwilml]

This sounds way to familiar. My regular cab LLY does that same thing. I'm convinced mine is a fuel knock. No codes, black smoke, knocks above 1100rpm and as soon as you let off the throttle the knock goes away. Some days are worse then others. I'm interested to see if a new injector(s) fix your problem.

I had these exact same symptoms on my lbz, some days worse then others.. So finally this past summer I changed out the injector that was showing a bad balance rate and it's been perfect since then..

 

[DURAMAXD219]

Just wanted to give an update on mine. Pulled the number 2 injector and it appeared the body was cracked, it was very wet. Popped a new injector in and all the knocking and smoke went away. Sold the truck the next week.