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lets talk about fuel pump timing

Discussion in '1982-Present GM Diesel' started by colbystephens, Mar 12, 2007.

  1. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    ok, so in a couple weeks i'm going to pull my engine out and deal with some seals and such. ever since i got my engine running, i've wondered if my fuel pump timing is slightly retarded, because i consistently have smokey start ups w/ good plugs, 2 VERY strong batteries and a good starter. anyway, is the timing considered to be advanced when the mark on the pump is clockwise of the timing mark, or counterclockwise of it? any advantage to advancing the pump a bit? school me on effects of different changes in pump timing.
     
  2. kennyw

    kennyw N9PHW Premium Member

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    Take it in and spend the $30-40 to get it set right. The equipment for setting the timing is expensive but getting it adjusted shouldn't be. The only way you will ever know its right is to have it set then mark it.
     
  3. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    i take it to a gm dealership? this is the adjustment done after the cover is on and the truck is driveable, right?
     
  4. kennyw

    kennyw N9PHW Premium Member

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    Look for a smaller diesel repair shop rather than the dealer. Timing is set with everything up and running.
     
  5. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    so, clockwise or counterclockwise is advanced? what are effects of having it set differently than dead on?
     
  6. kennyw

    kennyw N9PHW Premium Member

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    The lines on your motor are only dead on if the injector pump is original to the motor and nothing has ever been rebuilt. Once you pull it apart and start rebuilding/swapping parts it all changes slightly. I don't know which way is which, but just lining up the timing marks is not always right. Its just the right place to start before checking the timing.
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you feel like experimenting the way you know the timing is getting more advanced is that the motor is louder as far as the diesel clatter goes. mine is probably a hair too advanced and sounds like an older 6BT when it's cold. It's even relatively more clattery than the average 6.2 I hear.

    When standing in front of the truck you rotate the pump to your right to advance (clockwise) Don't go more than the width on the scribe line past the line on the cover. A little is a lot...

    Rene
     
  8. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    hmmmmm... maybe i'm not clear. i'm talking about the actual gear drive. :) i've got the pump rotated to what's been working well, but i think it's maybe a tick retarded on the actual gear line up.
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The "gear line up" as you call it isn't adjustable. To advance timing you rotate the pump...that's it.

    Rene
     
  10. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    good tip! thanks. i won't screw with that then. :)
     
  11. ssped

    ssped 1/2 ton status GMOTM Winner

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    So for performance should you advance it or retard it? can you raise fuel pressure or anything?
     
  12. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    You advance the timing. But as Rene said a little goes a long way. You don't turn up the pressure on that style of pump you turn up the amount of fuel delivered (fuel volume). But you can only go so far on that too. On a pump test stand that amount is measured in cc's per XXX number of pump strokes.

    George
     
  13. ssped

    ssped 1/2 ton status GMOTM Winner

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    I take it that I should be getting a bit of black smoke under full throttle and I am not. it runs really smooth and is not noisy at all. Where is the volume adjustment(I am sure I can look it up) and will it run better with a little richer mixture? I know on a gas motor you want to run them a little lean for performance but I also know Diesels are totally different. I am not looking for a big difference but I have a feeling she is running a little lean.
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    "Lean" and "Rich" are terms that don't really apply to a diesel. What you want to turn up is the fuel rate, and a search here should turn up that info. A few guys here have turned up the fuel rate as much as 1/4 turn with good results. Moving the timing a bit will also help...just remember it's not like a distributor where 1/2" isn't any big deal. 1 or 2 mm is a lot, and you'll notice the clatter get much louder as you advance the pump timing. Too much is a bad thing...

    Rene
     
  15. ssped

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    Thanks. I am going to go play a little.
     

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