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Spark woes

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Old 11-19-2016, 09:01 PM
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Spark woes

First off thank you to fmc400 and filthy beast for their insight in previous posts.

My situation went from running truck to truck sounding like fuel deprived to not starting. Replaced fuel filter, visually confirmed spray into carburetor upon activation of throttle, confirmed clean fuel coming from fuel tank.
Fuel delivery confirmed red herring
Next I replaced the distributor cap and rotor button, cap had oxidation on terminals and button had collected some carbon or metallic dust. No help, maybe distributor bad???

Testing phase results:
Org and purple from dist (stator?) 600ohm resistance with Key off
Coil positive 6vdc key on
Coil negative/blink test/tach test results "blinking" confirming ICM, wiring, voltage to coil
Primary coil resistance .5-1 ohms
Secondary coil resistance 11k ohm

Any thoughts as to what I'm missing?
 
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Old 11-19-2016, 09:27 PM
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bad coil wire? Have you pulled one of the plug wires at the plug and confirmed actual spark there?
 
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Old 11-19-2016, 09:43 PM
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No, because the carb backfired some gas up on the manifold while I used starter fluid to crank the engine, after replacing the fuel filter. I have alway been reluctant to use that method for fear of electro shock and fire. Any other way to test the spark from the coil to the plug?
Thank you for the advice
 
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Old 11-19-2016, 10:37 PM
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they sell in-line spark testers
you could put your timing light on the wire, if it flashes, it is firing...
 
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Old 11-20-2016, 07:44 AM
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Orange wire to ground with key off should show over 70,000 ohms. Purple to ground should show the same. Black to ground should show 0 ohms.

Something else to check.
 
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Old 11-20-2016, 10:17 AM
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Is that to test resistance on the stator?
Thank you
 
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Old 11-20-2016, 10:49 AM
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Yes it is. The manual also says the vacuum advance should be operated while checking the black to ground, to see if the fault shows up when vac advance is doing its thing. Flex the other wires while testing too, to see if the #'s you get stay the same.
 
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Old 11-20-2016, 12:10 PM
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Mine was running poorly but fired great so I pulled the plugs. The plug on the right is completely solid with carbon
 
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Old 11-20-2016, 04:11 PM
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ScottScott
Updated Testing results of the stator in key on position show that without advancing the vacuum manually neither org or purple react. However black to ground shows zero ohms. Upon Typing this out however leads me to conclude that I should be testing this while manually actuating the advance, anyone concur? Testing the org to purple shows resistance between .5-1 ohms. Next up to test spark plugs.
 
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Old 11-20-2016, 04:40 PM
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Don't worry about the vacuum advance at all. It's only a load related, vacuum to mechanical gizmo-pete which only operates when the engine is running. Has no value on these resistance tests.

Stator ohms - orange to purple = 400 - 1K ohms. Orange and/or purple wires to ground = > 70K ohms, as scottscott said.

Your stator test - orange to purple test showing 0.5 - 1 ohm means the stator is kaput.....see above. How could it go bad from your previous test? That's curious!

Oh, and you're welcome. Hope we can figure out this ilness
 
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Old 11-20-2016, 04:47 PM
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The reason you want to activate the vacuum advance while testing the wires is that the wires move as the vacuum advance does its thing. That flexing of the wires as the vac advance moves the plate can create an intermittent break in the wire.

Also stator tests should be done with the key off.
 
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Old 11-20-2016, 05:01 PM
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Originally Posted by scottscott
The reason you want to activate the vacuum advance while testing the wires is that the wires move as the vacuum advance does its thing. That flexing of the wires as the vac advance moves the plate can create an intermittent break in the wire.

Also stator tests should be done with the key off.

All correct. Brittle wires/connections can be found on the breaker plate whilst moving it by hand...or the vacuum arm.

Re-read your post #9....make SURE the key is OFF....no voltage anywhere when doing resistance tests. Sure fire way to throw readings off and blow yer DVOM!!
 
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Old 11-20-2016, 05:11 PM
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Djstright: Holy shades of Al Jolson!

How was that puppy running at all?
 
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Old 11-20-2016, 09:00 PM
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Ok, so the ohm setting was 1k on my tester, then with the reading between .5-1, would have been 500-1k ohm.

Next to check the plugs.

Thank you
 
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Old 11-21-2016, 03:44 PM
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Update: replaced stator as above mentioned testing provided sketchy results. Cold start, got it running,...poorly, wouldn't idle without quarter throttle.
Also as I left off the key the engine would hit and almost turn over?!
Considering the ballast resistor wire of doom, but 6vdc coming into the coil + as should be when key of eng off. Blinking when ground at coil - tested during start.
Pulling my hair off on this one
Next steps checking spark plugs for carbon buildup.
 

Last edited by BigMightySam5600; 11-21-2016 at 03:47 PM. Reason: Forgot to mention


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