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06-05-2010, 01:23 PM #1
Strobe can't find timing marks for #1 cylinder
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?
06-05-2010, 01:57 PM #2
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.Still Loyal to GM after all these years...:shocked:
2006 Impala LT 3.5L
2005 Silverado WT small cab/longbed 4x4 4.3L V6
1999 Grand Am 3.4L in TX w/ our youngest
1993 GMC Jimmy 4.3L 4 door 4x4 'Ole Rusty' - 'SOLD'
1988 S-10 small cab/longbed HT3.4L Crate Engine
1970 Nova 250 I-6, factory 3 sp floor shifter.
1968 Chevelle 'Nomad' Wagon 250 I-6 w/ 3 on da' tree.
06-05-2010, 02:04 PM #3
1984 Chevrolet C-20 Suburban.
No computer. The air filter housing instructed me to disconnect & plug the vacuum advance, which I did.
06-05-2010, 02:06 PM #4
06-05-2010, 02:06 PM #5
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Out of curiosity why ya checking the timing?
Is there a miss or some other issue?
06-05-2010, 02:12 PM #6
Checking the timing was supposed to be the easy check.
06-05-2010, 02:15 PM #7
Last edited by TomW; 06-05-2010 at 02:23 PM.
06-05-2010, 02:30 PM #8
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...
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when in doubt, doubletap !
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06-05-2010, 02:43 PM #9
06-05-2010, 03:11 PM #10
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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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