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Bad signal from injector


Dan107
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Evening everyone.  I have a 2012 Pinnacle CXU613, MP8.  I was unloading my pneumatic trailer yesterday and noticed the engine began making excessive noise.  I initially thought something internal was about to fail.  The noise quieted down somewhat, and on the way back home, I only noticed it when the truck was at idle.  I put the computer on it today and there was an inactive injector code related to a bad signal.  Through diagnostics, (cylinder balance reset, and compression test)  I found that #1 and #6 cylinders are outside of normal (big red bars on the graph) with #1 being the worse of the two.  I ran an overhead on it, and did another compression test with the same results.  My question is; does this mean I need to do an in-frame?  Is there any other tests that I could run to help me determine if this is needed?  Any help would be greatly appreciated.  

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I have seen the engine brake plunger/pistons unscrew themselves causing this issue. Also with that high of miles I’d really look for broken valve springs and for the intake and  exhaust valves to start wearing up into the valve seats. Especially check this if the engine has been deleted. 

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I forgot to add, the head was rebuilt last year at this time with all the seats, guides and valves replaced.  #2 liner cracked and I had to replace it.  Also, there is no smoke, or oil consumption from the engine.  I did check the springs yesterday, and they all look good.  

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13 hours ago, Dan107 said:

Evening everyone.  I have a 2012 Pinnacle CXU613, MP8.  I was unloading my pneumatic trailer yesterday and noticed the engine began making excessive noise.  I initially thought something internal was about to fail.  The noise quieted down somewhat, and on the way back home, I only noticed it when the truck was at idle.  I put the computer on it today and there was an inactive injector code related to a bad signal.  Through diagnostics, (cylinder balance reset, and compression test)  I found that #1 and #6 cylinders are outside of normal (big red bars on the graph) with #1 being the worse of the two.  I ran an overhead on it, and did another compression test with the same results.  My question is; does this mean I need to do an in-frame?  Is there any other tests that I could run to help me determine if this is needed?  Any help would be greatly appreciated.  

I'm not to educated on mp engines but if they are like any other diesel engine, I would assume that a cylinder balance or contribution test with failed compression will cause the engine to speed up where the compression stroke happens in the dead cylinder , it's an audible speed change when cranking.did you test compression with a known good analog gauge or just electronically? 

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4 hours ago, Dan107 said:

I forgot to add, the head was rebuilt last year at this time with all the seats, guides and valves replaced.  #2 liner cracked and I had to replace it.  Also, there is no smoke, or oil consumption from the engine.  I did check the springs yesterday, and they all look good.  

Mack pros got a point!

To the un trained eye I the engine brake slaves would not be easily noticed! You claimed to of done a valve set did you adjust much on the 1-6 we usually catch this issue when doing a valve set It shows up as a real  tight engine brake set on the offending cyls! 

Also it is possible  you got some pin fretting  or rotten wire on those two injectors causing the codes ! possibly unrelated to the noise!

Just sayin

Edited by fjh
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1 hour ago, fjh said:

Mack pros got a point!

To the un trained eye I the engine brake slaves would not be easily noticed! You claimed to of done a valve set did you adjust much on the 1-6 we usually catch this issue when doing a valve set It shows up as a real  tight engine brake set on the offending cyls! 

Also it is possible  you got some pin fretting  or rotten wire on those two injectors causing the codes ! possibly unrelated to the noise!

Just sayin

Thanks for the help everyone!  To answer this, yes 1 and 6 were tight and there is also cracked wire shielding as well.  I'm going to address these two issues and try again.  

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The rocker arm assembly must be removed check them ALL! There is a special tool made to hold the slave While repairing it however you can get by with some aluminum soft jaws in a vice!

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Okay, so I'm also replacing the two injector cups while I'm here.  I pulled the #1 cup and the injector hole filled with coolant.  I don't recall this happening when I originally replaced the sleeves and injectors.  Do I have something else going on?  Head gasket???  

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New injector cups installed on #1 and #6.  Cleaned and serviced the plungers.  Put it back together and the injector harness cracked and frayed to the point it is beyond repair.  The connectors on some are coming apart!  $1484.82 for a new harness because Mack/Volvo doesn't think it practical for a connection and separate injector harness!  Turbo in December, now this!

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14 hours ago, Dan107 said:

New injector cups installed on #1 and #6.  Cleaned and serviced the plungers.  Put it back together and the injector harness cracked and frayed to the point it is beyond repair.  The connectors on some are coming apart!  $1484.82 for a new harness because Mack/Volvo doesn't think it practical for a connection and separate injector harness!  Turbo in December, now this!

Yup you have to by a new truck if you want a new practical connection!

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