Strobe can't find timing marks for #1 cylinder

Discussion in 'General Chevy & GM Tech Questions' started by TomW, Jun 5, 2010.

  1. TomW

    TomW New Member

    I went out to check the timing on my 454 this afternoon, and the strobe light could not find the mark on the harmonic balancer even after I verified the strobe was connected to cylinder number one's spark plug wire.

    The only work done up until this point was to pull & clean the rotor and check the cap for cracks. Both the rotor and distributor cap only go on one way, so I don't think I screwed up anything there. The truck fired right up afterwards.

    Out of curiosity, the strobe's inductive pickup was moved from wire to wire until the timing mark was finally visible after connecting to cylinder seven's wire. This cylinder is six cylinders away in the CW firing order (1 8 4 3 6 5 7 2).

    Everything was fine two years ago when the timing was last checked.

    The harmonic balancer looks okay and does not appear loose in its mounting.

    If I were to trust what is lighting up while connected to plug #7, the timing is off two degrees.

    Would anyone care to offer insight into what has happened?

  2. wis bang

    wis bang Rockstar 100 Posts

    What year truck? The OBD I units need to disconnect the computer b/4 checking the base timing...My '88 S-10 had a wire under the glovebox at the top of the carpet that had to be unplugged to stop the computer from adjusting the timing. Plugging it in w/ the timing light connected cause the mark to disapear...

    I'd bet this is also required for the newer units w/ OBD II computer since the computer still adjusts the timing.
  3. TomW

    TomW New Member

    1984 Chevrolet C-20 Suburban.

    No computer. The air filter housing instructed me to disconnect & plug the vacuum advance, which I did.

  4. wis bang

    wis bang Rockstar 100 Posts

    That will do it...after checking and locking the dist, we used to hook it back up to test the advance...sounds like you already did that.
  5. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Out of curiosity why ya checking the timing?
    Is there a miss or some other issue?
  6. TomW

    TomW New Member

    Yep. The whole thing is odd, though. I'm hoping I'm chasing a problem that's due to bad gas. But even though the Mighty Burb is my primary tow vehicle, it does have lotsa miles on it, and I'm trying to rule out a burned valve.

    Checking the timing was supposed to be the easy check.

  7. TomW

    TomW New Member

    The truck occasionally flutters or backfires through the carb when the secondaries open while towing a travel trailer.

    I'm guilty of buying cheap gas, though (a practice I am about to stop with this vintage vehicle) but I want to rule out a burnt valve.

    Last edited: Jun 5, 2010
  8. trapperdon

    trapperdon Rockstar 100 Posts

    on the balancer, are you using a piece of chalk to ensure you're seeing what you think is right?

    did you try dialling it in anyways on the #1 plug until it was visable?
    you sometimes gotta do the stutter & rev method just to get feel for the min/ max...

    when you checked cap, did you take an emery board and sand down the contacts to clean them?

    try pulling the #1 plug (put back into wire) & hold to ground on block to see if you're getting spark..

    something aint done right on plugging your vacuum advance if it doesnt show at all...

    FUEL additive.... stp, gummout, LUCASOIL .....
  9. TomW

    TomW New Member




    HEI is there.

    I hear you, brother. Like I said, checking the timing was supposed to be the easy part.

    LucasOil? get outta here... STP sounds good though.

  10. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Boy,I should probably just butt out, since I haven't had to use a timing light in 30 years or so.

    However, any chance number 1 and number 7 actually fire at the same time, or more likely fire exactly 360 degrees apart? Waaaay back when some electronic ignitions fired on every cylinder every rotation despite the spark only being needed every 720 degrees.

    If this was so, of course you should still see a firing-and your inductive gun should fire-on plug one. So is it possible that plug one-the spark plug wire- is BAD?? And the plug 7 wire fires the same time as one, so it reads the same as number one would, if one was working right??

    I'm really just guessing here, but if 7 is right, it must fire the same as one?? Maybe??
    Maybe just bad wire bad plug on number one?? This would make it run like crap of course??


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