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6.2 pump timing

Discussion in 'The Garage' started by jwglover, May 3, 2007.

  1. jwglover

    jwglover Registered Member

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    I have an 87 crewcab with a 6.2, I bought it with 68 k, 90 k now, it had new pump,injectors,fuel filter,and some other stuff, replaced before i bought it, so I fugured everything was good, or someone was chasing a problem.
    I have driven other 6.2 and they seem to have a lot more power than mine does. At first the eng would over heat ( up to 220 degress very easily ) and never started very well,and the eng always seems like a small block with the timing retarded on it.
    A shop said to turn up the pump timing, I did turn up the fuel and did rotate the pump, both helped ( it never over heats now ) and does start and run better.I have the pump turn as far as I can ( the pump hits the intake when turn as far as it can ).They only said to move it an 1/8 to a 1/4 of an inch. I moved it as far as it would go.
    My question : could whoever put the pump in, may have got it a tooth off ?
    and how can I check the timing, ( again the eng has always seemed like a small block with the timing retarded )
    also can I advance the timing one tooth to to make it run better ?
    Teh biggest question is how to check the timing ?
     
  2. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    First this belongs in the diesel forum. Yeah buy a membership.

    Timing is done with a timing light and an adapter from the number one injection line. All the dealers have the adapter and most diesel injection shops do too.
    George
     
  3. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    that's just rediculous. that means every post that regards your vehicle belongs in the 73-91 forum, and if you've got fuel injection, then every post about your engine belongs in the injection section... we'll never have any posts in the garage.

    i suspect you've got the injector too far forward. mine is about 1/8 inch forward and is really good. for about $40 you can have the gm techs finish timing it for you - i haven't done that to mine, but another ck5er who's into the 6.2's swears by it.

    why did you rotate the pump as far as it would go? did you try other locations?

    the 6.2, to my knowledge, will not run if the pump timing is off by a tooth on the gears. you can't advance the teeth to get better power.

    here's a thread regarding fuel pump timing that i started in the diesel forum:
    http://www.coloradok5.com/forums/showthread.php?t=201804&highlight=fuel+pump+timing
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    It's not like timing on a gasser. 1/16" of an inch on the IP makes a huge difference!! There is a scribe mark on the IP and the timing chain cover where it bolts up. Ideally those lines should be lined up dead even.

    Rene
     
  5. jwglover

    jwglover Registered Member

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    when the -'timing marks' were lined up, it hardly would start (crank for ever )
    I moved little by little, thats what the shop said ,1/16'' is a lot,,, well that didnt do anything,, a 1/2 ''made the difference ! Thats why I wondered if the timing wasnt correct in one way or another. it does start very easy (within seconds instead of 30-45 seconds )
    I will read that post on timing a 6.2,, thanks
    and to Smalltruck.... buy a membership ?? well I have been on and off this website for about 5 years,, and this is the first time I have gotten a educated response for any question that I have ever had. thanks to colbystephens,
     
  6. jwglover

    jwglover Registered Member

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    So ,, that post really didnt answer my question either,, : if someone put in the pump, is there anyway that they could of put it in one tooth off ? and how do they check to see if they put the pump in correctly ?
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    You can't put the pump in "one tooth off". There is an alignment dowel and three bolts attaching the pump driver to the timing gears.

    Those marks are guides though, for proper timing it does need to go into a diesel shop where they use a luminosity probe to fine tune timing.

    How old/worn are the injectors and the IP? When mine were in need of a rebuild it was hard starting and smoked like a train for quite a while. Bumping the timing helped...but ultimately getting the IP and injectors rebuilt did the trick. When I re-installed the IP and injectors I baselined the timing by putting the pump mark about 1/16" past the housing mark. It was very loud and clattery...12V Cummins loud. I backed the timing off the 1/16" and it sounded normal again, although still a touch loud compared to other 6.2's I've heard.

    Rene
     
  8. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    **ahem** :whistle:

    your very question was asked. :wink1:
     
  9. smalltruckbigcid

    smalltruckbigcid 1/2 ton status

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    The other thing about having the pump that far advanced is its really hard on the pistons. I think the advance in the pump is messed up. You could take the truck to someone and have them check the advance with a timing setup. I think all that would do is cost you extra money to find out you're way to far advanced.

    Where I live in Minnesota getting a pump recalibrated costs $150. plus seals. If you have any broken internal parts they are extra. You can buy a rebuilt off ebay for about $275 plus shipping.

    To need as much advance as you describe either the compression is low or the advance mechanism in the pump is messed up.

    Hope that helps
    George
     
  10. jwglover

    jwglover Registered Member

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    Thank you both very much.
     
  11. twodollars

    twodollars Registered Member

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    The pump drive flange is keyed with a pin, so that can't really be off, but the actual pump drive gear that the pump flange bolts to can be off a tooth. It is driven by an additional gear next to the cam drive gear. The best answer is to get it checked using a tach n time or time track, and see where you are. You should shoot for about 3.5-4.0 degrees at 1500, and off of the cold start advance. If the timing numbers look good when you check it, just run itn like it is, or you could pull the front cover off and check the timing marks on the drive gear.
     
  12. k204dr

    k204dr 1/2 ton status

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    ideally the timing marks line up, but i had marks lining up on my motor, and then the pump went out. put in a reman pump off another motor that blew up on me, and had to advance it past the line about an 1/8 for it to run decent. you have to redo the line when you get it timed with the new pump on. I have yet to do it on mine, but any diesel shop can set the timing for you, and its highly recommended.
    theres also a really good 6.2 forum here: http://www.dieselplace.com/forum/index.php
    and you need to search there on how to check the timing advance to see if its working. that would make the power low. ;)
     

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