Cause of Broken Injector

Discussion in 'Trucks [ Eighteen Wheelers ]' started by underpsi, Feb 28, 2012.

  1. underpsi

    underpsi Road Train Member

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    Sep 18, 2008
    Toronto, Ont
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    [​IMG]

    Here's what I know. The injector hold down bolt broke allowing the injector to move and bounce around. The injector solenoid somehow unthreaded itself and came apart. Somehow the adjustment screw on the injector rocker threaded out and broke some pieces of thread near the top of the rocker. The driver definitely drove the truck too long with it broken. The crankcase is full of fuel.

    Here's some questions maybe you guys can help me figure out.

    Lets say the injector hold down bolt broke allowing the injector to move around and possibly bouncing up and damaging the injector adjustment screw on the rocker, how could the solenoid come apart like that?

    I'm not even sure how the injector adjustment screw could come out like that either, with it in the proper place there should be plenty of threads on the screw and theres also the jam nut to hold it in place.

    How long do you think the engine could run with the crankcase full of diesel without damage to the main and rod bearings? The rocker arm bushings look fine from a quick glance.

    Heres a picture of the damage done to the injector rocker and you can also see the mark the adjustment screw made on the top of the spring. The same mark is on the bottom of the adjustment screw like they were smashing into each other as opposed to just a slight hit and pushing like it would normally be.
    [​IMG]

    Heres a pic of the marks in the head from the injector moving around. I'm guessing bare minimum to save this head its gonna need a new injector cup and hopefully there isn't internal damage in the injector bore itself
    [​IMG]

    Let me know what you guys think could have caused this

    I'm thinking the last person to do the adjustment on that injector didn't do it right possible sending extra shock through the injector and breaking the hold down bolt. Then the driver not stoping when he noticed the problem causing even more damage from the injector moving around and possbily the reason the solenoid maybe came apart.
     
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  3. Starline

    Starline Medium Load Member

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    You don't say how long the driver drove the truck with the bad injector or how long you had diesel in your oil.

    I feel for you man....

    I had an injector solenoid seal go out on me last Sept. I had drained 2 gals when I discovered the problem and another 2 gals 50 miles later when I finally got to a shop. I thank god I had synthetic.

    I had the same fear.. washed out main bearings, but so far so good and my oil pressure is still good with 838K miles on her.

    I wish I had the answers your looking for and wish you well...
     
    underpsi Thanks this.
  4. Dutch

    Dutch Light Load Member

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    Have the injectors been replaced lately or in the past? You have to replace the injector hold down bolts when you change injectors.
     
  5. Jas

    Jas Medium Load Member

    How much diesel was in the sump? if it has logged any low oil pressure codes or if there was more than 4 gallons of diesel in the sump I would check the big ends and mains, bearing are a lot cheaper than crankshafts.
    Its unlikely that it ran far once the hold down bolt broke, they usually dont take long to fill the sump with diesel and start dropping oil pressure and they knock like crazy and blow lots of white smoke.
    When was the last time it had the injectors out?
    When was the last time it had a valve adjustment?
    I have never seen an injector solenoid wind out like that before but the injector gets hammered once a hold down bolt breaks especially with the adjuster screw missing allow clearance to the injector where an injector normally has preload.
    How tight are the jam nuts on the other injectors in the motor?
    Based on those pics alone and without personally inspecting the failed parts I would guess the following has happened...
    The jam nut was not tight enough after the injector was last adjusted, the nut came loose allowing the adjuster screw to come out of the rocker, with those rockers the injector will still be actuated by rocker arm even without the adjuster in it. This missing adjuster mean there is now lash on the injector rather than preload, over time this has caused bending loads on the injector bolt as combustion pressure is trying to push the injector out, without preload from the rocker arm this puts much more stress on the bolt, the bolt has fatigued and fractured allowing the injector to come out of the hole and dump diesel in the sump, the rest of the damage including the solenoid coming out has happend after the bolt broke before the engine was shut down.
    Maybe take a close up picture of the end of the bolt that is broken so we can see what type of fracture it is, that might give more clues.
    And as Dutch said, you always replace the bolts whenever you have the injectors out, although most will be fine every now and then one wont be.
     
    underpsi Thanks this.
  6. underpsi

    underpsi Road Train Member

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    Toronto, Ont
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    The whole engine was rebuilt probably no sooner then 10,000kms before this. We had a small local guy do it and obviously it didn't work out well for us. He used the same injectors that he took out, whether he used new hold down bolts or not im not sure. My guess is he used the old bolts and didn't do the overhead properly when putting it back together. I already have the rockers off 3&4 but im gonna check the adjustment on 1&2 and 5&6 just to see how they are.

    Driver said the truck was knocking pretty bad. I checked the critical events and it had very low oil psi logged for about 2 minutes. Since it doesn't log the low oil psi warning i have no idea how long that was on for, I just know it was less then an hour. I haven't drained the oil/fuel out of the pan yet I'll be doing that today and find out how much extra "oil" is in there.

    So the bottom end should be fine if when i drop the oil it has no more then 4 extra gallons? What do you guys think?
     
  7. swaan

    swaan Road Train Member

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    You know I would not chance it. Drop the pan pull a couple of caps just to make sure, then you know. Costs the price of a pan gasket and a few hours labor.
    From this day on it will always be in the back of your mind if you don't.
    At leased it would be in mine. JMO!
     
  8. mgfg

    mgfg Road Train Member

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    I'd be doing an oil sample for sure.

    Does anyone plasti-guage bearings any more or am I showing my age? If so do the roads and mains.

    Low "oil pressure" for 2 mins>I'd be very concerned at this point in time.

    Does the guy that did the work have good insurance>you might need to know the name of his broker/agent>
     
  9. underpsi

    underpsi Road Train Member

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    I just double checked the critical events, it was very low oil psi for 9 seconds with and the lowest at 27psi and average of 33psi
     
  10. Mr. Haney

    Mr. Haney Road Train Member

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    Looking at this picture, Id say the bolt holding the injector down was loose. If you look at the area where the square end of the injector clamp sits on the head, you can see where is was slammed up and down. I don't think this wear patterned happened after the injector hold down bolt broke. As soon as the bolt broke the injector was popped up out of the head far enough to make the driver stop. I think it ran for a considerable amount of time with a loose bolt. The driver ignored the fact the engine wasn't running properly until the pounding of the injector in the bore started breaking things. I've actually seen them rain fuel out of the stacks with a loose bolt before, all the while pouring white smoke out the exhaust and knocking bad without breaking anything in the valve train or the injector.

    If the driver was my employee, he wouldn't be after seeing this carnage. He drove it for more time than was needed to find a safe place to stop with the bolt loose in my opinion. These engines pump roughly 2.25 gallons of fuel per minute from the tank to the engine with a stock fuel system. You find an extra 4-5 gallons of fuel in the oil, that would have me seriously think he drove the truck 2 minutes or longer with the loose hold down bolt.

    You need to try to inspect where the injector seats in the head for damage or fretting from the beating it took. If there is any damage you may never get the injector to seal the combustion gases from coming up into the fuel rail in the head.

    Looking at how little oil is in the valve cover area and how clean everything is, the oil is very diluted in the pan with fuel

    The oil pressure warnings would have me checking bearings
     
    underpsi Thanks this.
  11. underpsi

    underpsi Road Train Member

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    Toronto, Ont
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    You think if I pull a rod cap or two and main cap or two and check the bearing and they look good that they will be fine to use? There's little to no mileage on them so they shouldn't have very much regular wear and if there is any scoring from the fuel they will be coming out.

    I'm gonna replace the one injector cup and seals, we have a set of 57's that I'm gonna put in and just run a 550 1lw file as opposed to the 5ek file so that it will still be about 550hp. Drop the pan and check a couple mains and rods, hopefully just put a new gasket back on the pan and put it all back together.

    Hoping that after replacing the one cup the new injector will seat fine in the head and the seals will hold. Obviously using new injector seals and bolts with all the other injectors and running a complete overhead.

    What would happen if the injector didn't seal properly. If combustion was goin into the fuel rail of the head would it even idle properly then.
     
    Last edited: Feb 29, 2012
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