how to fix hard/no start/missfire/intermittent loss of ignition system

Discussion in 'Tech Info' started by misspooh, Dec 27, 2012.

  1. misspooh

    misspooh Member

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    There are an extreem amount of people on this forum that are suffering from this problem.

    This took me three weeks and a lot of money to figure out.

    Models:
    1999-2000 cadillac escalade
    1995-2000 chevy/gm S/T models
    1996-2000 chevy/gm C/K, M/L, G, P models
    1996-2000 olds bravada
    all with 4.3l, 5.0l, 5.7l, 7.4l engines
    -VINs W, X, M, R, J - RPOs L35, LF6, L30, L31, L29

    If you suffer from:
    No, hard, or slow start, backfire or "kickback" during crank start "grinding or unusual noise during crank, DTC P0338 or, no DTC, or intermittent DTC not related to the issue. (Replace Crank shaft Position sensor)

    Condition:
    Backfire during crank/start
    "kickback" during crank/start
    "No/Rough start"
    slow/hard crank start
    cracked or broken block at starter boss
    broken flywheel/missing teeth/unusual wear
    starter broken not able to crank engine

    Cause:
    Crank shaft position sensor has been struck by the crank position gear/key on the crank shaft that is only intended to disrupt the magnetic feild to provide crank position. This will cause the ECM to command 50+ degrees of timing during crank causing cylinder pressure to build way beyond normal operating cylinder perssure causing sever damage to the starting components i.e. starter, flywheel and attaching hardware.

    Over the years the forward main bearings begin to settle/wear which is a normal condition and or the timming cover has become warrped or settled. This causes the crank shaft position sensor to rest on the cranksharft timing position gear/key effecting the output voltages of the sensor causing the timing to increse or decrease by as much as 50 degrees. Sometimes the condition occures once the vehicle reaches it's normal operating temperature.

    Effect:
    Either your vehicle will try to start, backfire and not start which would lead you to belive there is a timing issue and or start at a low rpm and studder until it steadys out at the correct rpm-this is also common or randomly start fine and other times not start all while not setting DTC code or setting random DTC codes!!!! Very difficult to find with scanner!

    Inspection:
    Using a 10mm socket remove retaining bolt located on crank shaft postion sensor braket found on the bottom of the timming cover just behind the harmonic ballancer.

    unclip the harness and remove the harness to allow access to the sensor.

    Remove the sensor with a slight tug and inspect.

    you should see no sratches/scrapes or abrasions!!!

    Replacement:
    replacement is absolutely required if any of the above conditions are found!!!

    New sensor includes shims used to correct this problem use both shims included.

    Lastley, in the new box that the new crank shaft position sensor comes in a tech sheet will include even more detailed instructions on how to properly shim sensor.

    Hope this helps, good luck!
     
    Last edited: Dec 27, 2012
  2. xanatost

    xanatost Full Access Member

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    I will have to check this out. Mine does this from time to time. Good call :)
     
  3. SunlitComet

    SunlitComet OBS Jedi-Do Good

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    Exactly who are the extreme amount of people suffering from this. From my time here I have seen it happen once that this tsb effected someone.

    ---------- Post added at 06:48 PM ---------- Previous post was at 06:19 PM ----------

    Further more you are qouting the tsb which mentions nothing about crank bearings wearing out and the sensor hitting another component. If you are going to quote a tsb quote the entire article verbatim. Dont change it or add things as you see fit to the tsb itself.
     
  4. misspooh

    misspooh Member

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    Thanks for the spelling correction first off.

    When I was having these issues for three weeks I searched and found alot of people describing alot of these symptoms and not finding any resolve.

    The info I posted will help people that can't figure out why there having what seems like ignition issues.

    Thanks.

    The above info was derived from TSB 00-06-04-014 dated april, 2000

    The portion that described the bearing/timing cover alignment/wear came from Jim Tallen a GM master mechanic at Don Mallen Chevy in CT. This was in a tech write-up he recieved from a GM tech rep when he was stumped by my issue.

    Just trying to help other people if this doesn't help you or you don't agree I appoligize.
     
    Last edited: Dec 27, 2012
  5. SunlitComet

    SunlitComet OBS Jedi-Do Good

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    I am sorry i cant buy that. do you have this technical writeup? the tsb for the crank sensor mentions nothing of the fact the timiming cover is warped or damage nor does it mention anything about worn out bearings either. in was strictly a faulty sensor. even went on in the 3.8l oldsmobile engine as well as the 4.3l, 5.0l, 5.7l and 7.4l truck/suv/chassis cabs. and even then, faulty sensor, nothing more. the only symptons that referred to the main bearings i have ever read about was related to cold engine start knocking noises. especially on engines with oil coolers. never in relation to the crank sensor. I am sorry but if the crank moves for or aft to adversly effect your crank sensor. your engine would be already suffering hard from bearing issues so bad it would be making all kinds of racket if even run at all.
     
  6. knoslf

    knoslf Full Access Member

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    Hmmm, I always wondered why my 99 Yukon has that 'kick back' from time to time as it turns over while cranking the motor, will have to look into that since ill be changing my stupid starter today hopefully lol.
     
  7. SunlitComet

    SunlitComet OBS Jedi-Do Good

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    When it is actively failing the rpm as read from a scanner will be very different compared to tachometer on dash.
     
  8. Petey!

    Petey! TYF Newbie

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    My truck will sometimes randomly not start. usually after it's been sitting a long time (cold). It will crank, might fire once or twice and then die, and then unless its cold again, if I crank it, it will sometimes fire randomly and never come close to starting (sometimes fires on some cylinders for a second or 2 after I've finished cranking). Most times it fires straight up, and sometimes it fires up so quickly the starter grinds a little.

    Guess I'll pull mine off an see how it looks. I was just assuming my fuel pump was dying
     
    Last edited: Feb 20, 2013
  9. SunlitComet

    SunlitComet OBS Jedi-Do Good

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    you can borrow a fuel pressure test kit from autozone for a refundable deposit of $150.
     
  10. 99Yukon4x4

    99Yukon4x4 Member

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    If the Crank Position sensor is bad, will you still have spark or not?
     

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