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7.3 Idi Non Turbo Runaway

  #16  
Old 11-06-2018, 11:52 PM
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Originally Posted by wtroger View Post
does it have a c6 behind it. If so it could be drinking tranny fluid.

How? Just curious.
 
  #17  
Old 11-07-2018, 02:08 AM
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My bad the diesel doesn’t have vacuum per se. The modulator valve gets its vacuum from a mechanical vacuum pump
 
  #18  
Old 11-07-2018, 03:20 AM
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I don't see how it could be a cylinder or head gasket issue, it sounds like whatever is fueling it is making it to all eight cylinders.

Either you used too small of rings/pistons or its your pump.

Db2's are notorious for having a problem where a plastic thrust type washer breaks and jams the governor, this was later updated to a metal one but nose rebuilders still use the old style due to cost.

I'd pull the top off the pump just incase the metering arm is stuck/jammed, make sure the arm in the front has resistance and isn't just flopping back and forth. It's the governor arm and pushes back towards the rear
 
  #19  
Old 11-07-2018, 09:04 AM
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its a 5 speed manual so thats a hard no. Pistons were at the machine shop when it was bored they said the clearances were perfectly in the middle of where they need to be it all seem good and tight when i put it together. iv checked the Governor its seems to be fine in both bumps from what i can tell but that doesn't mean much iv never looked in one be for now, every shop we have talked to says it sound more like a fuel related issue. Pretty sure the boss ordered a new reman injection pump last night so if it is in the pump we are about to find out.
 
  #20  
Old 11-07-2018, 09:38 AM
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Originally Posted by Riddletowing View Post
its a 5 speed manual so thats a hard no. Pistons were at the machine shop when it was bored they said the clearances were perfectly in the middle of where they need to be it all seem good and tight when i put it together. iv checked the Governor its seems to be fine in both bumps from what i can tell but that doesn't mean much iv never looked in one be for now, every shop we have talked to says it sound more like a fuel related issue. Pretty sure the boss ordered a new reman injection pump last night so if it is in the pump we are about to find out.
I doubt both injector pumps would have the same exact problems. White smoke is a symptom of too much fuel. Check your fuel return lines for restriction. The tank selector valve may be the source.
 
  #21  
Old 11-07-2018, 10:08 AM
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Db2's are notorious for having a problem where a plastic thrust type washer breaks and jams the governor, this was later updated to a metal one but nose rebuilders still use the old style due to cost.

I'd pull the top off the pump just incase the metering arm is stuck/jammed, make sure the arm in the front has resistance and isn't just flopping back and forth. It's the governor arm and pushes back towards the rear
The broken plastic piece caused a no-start condition, not a runaway, plus it's doubtful there's any unbroken ones running still and they're no longer available. It only came in the first couple years 6.9's were produced. And if someone installed the cover and the arm was not in the pulled in (run) position the engine will run away. Doubtful you got 2 pumps with the top cover put on wrong but you never can tell.
 
  #22  
Old 11-07-2018, 11:16 AM
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Fuel return line is not blocked made sure of that and it only has 1 tank. it got better when i swapped pumps first pump would idle and soon as i touched the throttle it would take off so i put this other pump on get it fired up let it idle for a bit to get all the air out and idle it up it came back gave it a few small revs and thought i was good raved it to id say 2000 rpms maby a little more and it took off. not sure why it was higher in the rpms that it done it with the second pump thats the only thing im thining its the pump everyone else that has looked at it says its fuel related could injectors be sticking at a higher rpm and not at idle?
 
  #23  
Old 11-07-2018, 02:18 PM
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Did disconnecting the FSS stop the runaway?
 
  #24  
Old 11-07-2018, 04:20 PM
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havnt had it running again to check that. boss is on the way back with a new pump we lost most pressure out of the injection pump lastnight so he just bough one so its one less thing to fail. checking voltage to the wires at the solenoid to make sure their getting full voltage
 
  #25  
Old 11-07-2018, 04:38 PM
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Are the crankshaft, camshaft and injector pump gears timed properly? I assume so because being off 1 tooth usually means the engine will not start. Never seen or heard of an IDI running away. I'm out of ideas here....
 
  #26  
Old 11-07-2018, 09:06 PM
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Originally Posted by Perk85F250 View Post
Are the crankshaft, camshaft and injector pump gears timed properly? I assume so because being off 1 tooth usually means the engine will not start. Never seen or heard of an IDI running away. I'm out of ideas here....
I'd definitely check all that, being as you just rebuilt the motor.
An IDI *will* run 1 tooth off on the IP. It will also run 180 degrees off on the IP-to-cam(and 160 and 200 degrees. I have no clue how, but it does).

Edit:
also, look down the intake. What does it look like? Tons of oil? Nothing much?
 
  #27  
Old 11-08-2018, 08:56 AM
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timing is right iv checked many times to insure its right. inside of intake is clean. putting new injection pump on today
 
  #28  
Old 11-08-2018, 11:36 PM
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This to me, having read the above comments seems to be a CDR valve issue. I know the heads and other various engine internals are all replaced, but to run away a ready source of oil or alternative fuel must be provided. The mist oil system in these engines is the only thing that could provide a sufficient source of oil to fuel the engine to a higher RPM. Now there are a few different symptoms that could outline this for sure.

1) Block off the CDR valve or simply remove it and put a dummy plug over the hole to eliminate the oil source. This has the benefit of either confirming the CDR is dumping misted oil into the intake or eliminating the only real source of oil in a burnable form that the engine can get a hold of.
2) If the above fails and the engine is still able to run away, then this must be an Injection pump issue. This part gets tricky, does it have cruise control? That could easily go ham and start playing with the fuel. Another source could be internal to the pump its self. This would require a rebuild of the pump by an experienced person. Not a DIY kinda thing when it gets this in depth.
3) If the above does not seem like you want to try yet, then you could try the following. Turn the key to on, push the pedal down and release before starting the engine. Let the glow plugs cycle then start the engine. If it idles fine and does not have some silly run away, then the High Idle is not the culprit. If you tap the pedal then start it after, and the engine revs like hell, then the high idle is involved in some way.

Hope you get luck and the CDR is puking oil.
 
  #29  
Old 11-09-2018, 09:01 AM
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the cdr valve is blocked of has been from the start no cablebs are hooked up to the throttle put new injection pump on yesterday putting everything else on far as accesorys so it can set and run hoping the new pump fixed it
 
  #30  
Old 11-09-2018, 10:29 AM
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This to me, having read the above comments seems to be a CDR valve issue.
Please explain, unless oil can suddenly defy gravity and fly uphill on its own, how does it flow through the CDR? The CDR is vented into the TOP of the sheet metal valley pan, then there's about a 2+ inch gap between the pan and the valley itself. The only thing a CDR can possible draw in is crankase fumes which it's designed to do. Nowhere in either a FoMoCo or Navistar shop manual is a CDR mentioned in the excess oil consumption diagnosis sections.

Riddletowing, it will be interesting to know what this finally turns out to be.
 

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