7.3 Engine RPM's?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Alaskaman, Jul 13, 2018.

  1. Alaskaman

    Alaskaman Registered User

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    Finally I have all the fuel leaks and Brakes fixed on my 1993 F250 7.3 IDI Turbo with a 5 speed.

    Took it out for the first test drive since I bought it and now I have a question about the RPM's.

    It will only go up to 3000 rpm's unless I'm going down hill wide open and it will creep up to 3100-3200 rpm's.

    Seems like I should have at least 3500 rpm's. If that is true, how can I adjust it up?
     
  2. Macrobb

    Macrobb Full Access Member

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    What does it go to in neutral, floored?
     
  3. Clb

    Clb Another old truck Supporting Member

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    Do not sustain "floored" for to long...
    Just in case you ya do not want to let out the rods.
     
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  4. Alaskaman

    Alaskaman Registered User

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    At 3000 rpm's, I can hold it there all day. My old 88 7.3 did that at 60 mph with the 3 speed automatic.

    I'll check floored in Neutral tomorrow and get back with you.
     
  5. Macrobb

    Macrobb Full Access Member

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    Uh... no. It's not a gasser. The IP has a governor in it which is below the "indefinate safe limit" of the engine. Typically around 3400-3600 RPM. My Ford owners manual states to keep the engine RPMs below 3750 RPM(higher than the governed limit).

    Flooring it will give it full fuel until it gets to about 3,000 RPM, at which point the IP will start throttling back fueling until it hits a steady-state(RPMs stay constant, fuel delivered is just enough to maintain that under current load) around 3400-3600.
     
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  6. Clb

    Clb Another old truck Supporting Member

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    Yessir
    In a perfect world, yer right.

    Now is an eng. That refuses to tach up in a perfect world?
    Do we know the op will know what a runaway sounds like?

    Don't forget Justin makes a 4k governor spring....

    Op check throttle linkage?
    Check ip linkage?
    Check timing?
    Check go pedal for full swing?
     
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  7. Macrobb

    Macrobb Full Access Member

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    My 110 came with a higher governor than that... It'd rev to 4500 at least.
    4K+ is where a rocker bolt wiggled loose:
     
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  8. Alaskaman

    Alaskaman Registered User

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    After my maiden trip today, I have found out the most likely problem, but don't know how to fix it.

    My tachometer is giving faulty readings. In neutral it will give up to 3600 RPM. However, when I'm driving it down the highway it may show 500 RPMs or 3000 RPM.

    Bad gauge or electronic sensor?

    I do know what a run away diesel sound like. I experienced it first-hand on my John Deere backhoe. Not a pretty experience.
     
  9. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    The first thing to try is the magnetic pickup that is on the upper part of the injector pump gear cover. Check to see if the magnet has debris on it. Check to see if the wires are bare and touching. You could buy another pickup if everything else checks out. Maybe someone else will have another test that you could do before you start buying new parts.
     
  10. MtnHaul

    MtnHaul Supporting Member Supporting Member

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    My tach recently went wonky on me. Just tried cleaning the pickup and connector, the wires look OK but little improvement, though there was some.
     

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