1st Generation Dodge Cummins 89-93 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with Rotary Injection Pumps

Low Power, Fuel Mileage Drop - Help Please

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  #21  
Old 10-15-2011, 07:37 PM
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Originally Posted by NadirPoint
Diesels don't make vacuum. That's why the older ones have vacuum pumps and the newer ones are all hydraulic/electric.
WHAT All 4 stroke piston engines create vacuum. diesels may not create much vacuum unlike a gas engines that create more vacuum. The only reason for the vacuum pump is to supply enough vacuum for brakes and vent doors in the heat and ac system.
 
  #22  
Old 10-15-2011, 09:37 PM
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OK then, maybe you'd care to explain how an AD working not working "correctly," supplying "low fuel pressure" will cause excessive amounts of black smoke:
Originally Posted by jwirth
Is your air dog working correctly? low fuel pressure (flow) can cause this.
 
  #23  
Old 10-15-2011, 10:05 PM
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Default Low Power, Fuel Mileage Drop - Help Please

With no throttle plates to restrict air flow there's no way to create vacuum in a diesel, no point in having throttle plates when they'd serve no purpose in a diesel. Diesels with out a turbo will create areas of lower pressure than atmosphere for atmospheric pressure to rush into the cylinder but still not technically a vacuum, diesels with a turbo create pressure greater than atmospheric even at idle... Otherwise you are correct in the aspect that with out a pump diesels wouldn't stand a chance at producing enough vacuum for any type of vacuum actuation.


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  #24  
Old 10-15-2011, 11:49 PM
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If you not getting correct amount of fuel to the injector pump it can cause the injector pump to also not have enough fuel pressure to atomize the fuel. Injector will dribble and cause black smoke. And lose of power due to not burning all the fuel.
 
  #25  
Old 10-15-2011, 11:58 PM
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Originally Posted by jwirth
If you not getting correct amount of fuel to the injector pump it can cause the injector pump to also not have enough fuel pressure to atomize the fuel.
The mechanically popped injectors in these trucks go at around 8,500psi, IIRC. Whether or not fuel atomizes is all up to the injector after that. That's why I was liking the broken tip idea, but nothing to do with fuel supply or IP, no matter how you slice it.
 
  #26  
Old 10-16-2011, 12:40 AM
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Default Low Power, Fuel Mileage Drop - Help Please

I think they're a little lower than 8500. I think the 2nd gens are around 8800. Low injector pump fuel supply pressure (especially in the VE) will cause delayed injection or basically retarded injection timing. If pop pressure is 6500 psi that injector isn't going to open until pressure peaks at around 6600. Simply; injector will atomize like clock work. Depending on supply pressure Pump may not deliver enough fuel to rapidly build line pressure and inject fuel as intended, when intended... Which will result in white smoke (unburnt fuel) or in essence severely retarded timing. Pair that with the VE which has a dynamic advance reliant on fuel pressure, no matter how low your fuel pressure you're going to end up with white smoke before black and more than likely popping from the delayed injection.


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  #27  
Old 10-16-2011, 12:44 AM
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Originally Posted by tower_ofpower
...no matter how low your fuel pressure you're going to end up with white smoke before black and more than likely popping from the delayed injection.
Thanks for that. Sometines I just don't verbalize properly.
 
  #28  
Old 10-16-2011, 02:10 AM
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you 2 can have a pissing contest all you want. my lift pump went out and blow BLACK smoke low rpm's. white smoke at HIGH 3000 rpm's. and lost power. And retarded time well cause black smoke, high egt's, and high boost. Don't believe me retard your pump 1/4 or more and see what happens. It will even smoke at idle. retarded that far. And pop pressure is around 3550 psi for injectors.

---AutoMerged DoublePost---

And back to the question asked.

"Poor performance, black smoke or low power. Improper fuel, Air in fuel system, intercooler internally blocked or leaking, Restricted or blocked fuel injectorlines, Incorrect injection pump timing, Restricted or damaged injector nozzle, Clogged or restricted air filter, Air fuel control tube leaking or broken, Low manifold pressure, Injector sequence does not correspond with firing order, Lower or uneven engine compression, Injection pump to engine timing, Fuel injection pump malfunction or not adjustable"
 

Last edited by jwirth; 10-16-2011 at 02:10 AM. Reason: Automerged Doublepost
  #29  
Old 10-16-2011, 02:14 AM
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Originally Posted by jwirth
If you not getting correct amount of fuel to the injector pump it can cause the injector pump to also not have enough fuel pressure to atomize the fuel. Injector will dribble and cause black smoke. And lose of power due to not burning all the fuel.
So it's really a timing issue, then?



Guessing's OK for the weird stuff, but A/F/Smoke is pretty basic. That's alot of guesses you got there!
 
  #30  
Old 10-16-2011, 02:27 AM
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Originally Posted by NadirPoint
So it's really a timing issue, then?

Guessing's OK for the weird stuff, but A/F/Smoke is pretty basic. That's alot of guesses you got there!
That guessing you call it is from the Chrysler service manual smartass.
 


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