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Thread: 6.5 blowing Blue.

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  1. #1
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    Default 6.5 blowing Blue.

    Hi all, having a bit of a problem with my 6.5, so did a compression test in the injector ports, came up with 6 cyl. at 250 and 3 at 200. So what might be my problem. Note tester would not hold and lock the reading, so picked the highest wile spinning.

  2. #2
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    What were the other 6 readings? What is the "bit of a problem"?
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  3. #3
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    Default Blue .

    Quote Originally Posted by JohnC View Post
    What were the other 6 readings? What is the "bit of a problem"?
    Right bank front to back 250, 200, 250, 250. Left 250, 200, 200, 250. So, what should my reedings be?
    Started pulling hoses, to remove the 6.5, it is in a boat so working out side.

  4. #4
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    O- yes what is the problem, pumping Blue smoke, searching for answers.
    ,

  5. #5
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    Blue smoke on a running/warm engine is most likely failed injection pump, and/or injectors. Compression low enough to cause smoke won't start (which is the primary symptom of low compression).

    I would start with questioning the compression test method. It should be done on a hot engine, through the glow plug holes (all plugs removed before quickly starting the test), and exactly 6 puffs at each cylinder. Cold engine testing is only good for trend tracking or identifying a catastrophic failure, but not actual compression values. Using a tester that doesn't hold the value is not useful, as a valid final value must be cumulative of the 6 puffs. However, if your test was minimally accurate, the compression is very low, and likely won't even allow a start w/o some serious help (ether, and/or a lot of heat). Any compression value below 300 PSI may become problematic. 250 PSI is marginally functional, while 200 PSI is in the basement. That many cylinders that low on an engine that starts and runs raises many flags, and the first reason I would question the test method.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  6. #6
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    For starters, most if not all compression testers will give wrong readings on our motor, for 200$ get a tester that will be accurate. Unique diesel has one that will work and give very accurate readings. FYI, a 18:1 motor with high mileage yelds around 350psi with the recommended 6 rotations, with as low of compression as you think you have I doubt it would start well .

  7. #7
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    Default Blue .

    Quote Originally Posted by sctrailrider View Post
    For starters, most if not all compression testers will give wrong readings on our motor, for 200$ get a tester that will be accurate. Unique diesel has one that will work and give very accurate readings. FYI, a 18:1 motor with high mileage yelds around 350psi with the recommended 6 rotations, with as low of compression as you think you have I doubt it would start well .
    Thank you, your suggestions tell me the test was not correct, so I will retest. Not the best to try and test with a warm Engine, in a boat that has been winterized and it gets into the freezing range at night, so will do the best I can. Engine is low HR and would start good, so problem is in the test. Next week temp is going up a bit so will try once more. The initial problem started after dummy me, overrevved the poor defenseless Engine, ( was testing props), to answer other question why not put it inside, no room, on the trailer 38ft. long. Thanks.

  8. #8
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    Quote Originally Posted by FKummert View Post
    overrevved the poor defenseless Engine...
    No governor?
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  9. #9
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    Governor? Part of the pump? Have mechanical pump. Ran up to 5000 before I cut it.

  10. #10
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    A short run up to 5K wouldn't likely hurt anything, but it is a sure indicator the pump was failed before the incident. Probably the reason for the blue smoke, and a run past the (pump-internal) governor.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  11. #11
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    Anyway, to check the pump other than on a test bank?

  12. #12
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    Simple, and it's in a boat, so it should be very simple. (this test works for most things Stanadyne) Remove the pump from the engine. Throw it into deep water. If it floats, it's good.

    Seriously, you've already tested the pump. No governor control and blue smoke. It's broken. The only need for a test bench is after an overhaul.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  13. #13
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    I agree 100%
    Governors on these should cut in before 5000 RPM.....

    My suggestion is to get the pump off the engine and get it to a shop that does stanadyne pumps.

    Scribe a mark across the pump and timing cover flanges so you can get the pump back close...

    Have the pump checked out and see wassssup.

    Getting it rebuilt can be a good choice.....The shop should be a certified stanadyne shop...
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  14. #14
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    Thank you, Robyn, we have a shop in Missoula that can. Now just need a weather window. All have a great Turky Day.

  15. #15
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    Your welcome.
    You too...
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  16. #16
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    To Robyn and all smarter than I. tested compression once more and I am getting the same low reading. Now it might help to tell all, this is a P400 18 to 1 compression engine, from Peninsular.
    Part of the fleet.
    85 Sub. 6.2 trans out.
    82 3/4 CC 6.5 N/A
    83 GMC 1 Ton 6.2 Est Mil. 1 MIL +
    96 Dodge 3500 5.9 4X4 Sorry, went to the dark side.
    19 Escalade Buick

  17. #17
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    The 18:1 engines can be a little smokey when cold....Should clear out as it warms up...

    Did the blue smoke issue start happening after the engine had been run for some time ??? or is this a fresh install ????

    Retarded timing will make tons of blue smoke.....

    How much time is on the engine ????
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  18. #18
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    Sorry for the long pause, thank you for the reply. The Engine has about 50 HR on it, there was no blue smote, prevue's runs, I was testing props and went from a 20 pitch to a 18 so that is why it over revved, I was watching for black smoke to roll off the back and not the tach. Thank you and Merry Christmas.
    Part of the fleet.
    85 Sub. 6.2 trans out.
    82 3/4 CC 6.5 N/A
    83 GMC 1 Ton 6.2 Est Mil. 1 MIL +
    96 Dodge 3500 5.9 4X4 Sorry, went to the dark side.
    19 Escalade Buick

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