12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

Valve question.

Old Mar 24, 2012 | 12:42 AM
  #21  
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Hopefully I will find it .

What should I look for if the lift pump is doing that? Yeah I could probably take a video and post her tomorrow!


1995 Ram 3500 4x4 5.9 12 Valve Automatic
4" Straight Pipe to 9" Stack
 
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Old Mar 24, 2012 | 02:36 PM
  #22  
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ya know myster i had a total brain laps i shoulda thought about the lift pump, vex hes right it could possibly be the lift pump
 
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Old Mar 24, 2012 | 04:57 PM
  #23  
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As in the lift pump is bad? What are the symptoms?


1995 Ram 3500 4x4 5.9 12 Valve Automatic
4" Straight Pipe to 9" Stack
 
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Old Mar 24, 2012 | 05:23 PM
  #24  
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No the pulsation of the lift pump causes the fuel lines to tick or knock if they are loose, sometimes they tick even when the lines are tight. If the spring in the pump fails it can tap or knock but generally causes low pressure as well.
Don't worry cummins un glued. I have times when ill over diagnose something I've fixed hundreds of times and chase my butt around the truck for hours at a time
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Last edited by mysterync; Mar 24, 2012 at 05:27 PM.
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Old Mar 24, 2012 | 09:50 PM
  #25  
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Oh I gotcha! I will check the lines and if the lift pump spring is ticking should i be able to hear it coming from the lift pump?

Thanks again for all the help guys!
 
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Old Mar 25, 2012 | 12:38 PM
  #26  
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Update!
So this morning I was looking at the lift pump and seeing if I could feel it pulsing with the knock that I am hearing and i couldn't feel anything like that.

So I was looking around the injection pump and I noticed the bolt holding the #1 fuel line to the injection pump looked a little wet. I tried tightening it but it was as tight as I could get it. But I loosened it and a little fuel started misting out and the knock went away! So the problem it somewhere on the #1 fuel line. Either the injector or something in the injection pump there?? Or I'm hoping it is just the timing is really retarded. I loosened all of the other fuel lines on the injection pump and nothing happened. Only the knock goes away on #1. And I did it multiple times instead of just once like in my above post.

Any thoughts are appreciated!!


1995 Ram 3500 4x4 5.9 12 Valve Automatic
4" Straight Pipe to 9" Stack
 
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Old Mar 25, 2012 | 12:50 PM
  #27  
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Whats your timing sitting at?
 
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Old Mar 25, 2012 | 12:58 PM
  #28  
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I would use the pin to see if its at factory timing. Then as said before switch injector 1 and say 4 and see if the knock moves. If it stays at 1 I would check delivery valve and compression on cylinder one. If it moves have your injectors replaced or serviced. If it stays and you rule out mechanical issues I would send the pump to the injection shop. While its possible to diagnose pump issues on the truck your really just running blind. You might have an educated guess but in the end a bench is required.

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Old Mar 25, 2012 | 02:58 PM
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^^ x2
 
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