Left key on, now won't start
09-20-2013, 01:19 PM
#21
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Thank you all for your replies. The coil is within spec when I checked it's resistance. Is it possible to have a bad coil that checks okay with an ohm meter? I will check the timing and compression, but I don't think it's mechanical since it ran fine before my boneheaded move of leaving the key on. My fsm states not to leave the key on for more than ten minutes but doesn't say why. Thank you for the education. Most of my experience is with carbureted engines.
09-20-2013, 08:42 PM
#22
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Generally, no, a coil will not test okay with an ohm meter and be bad. The voltage across it, and the resistance in the coil is what generates the high voltages to create sparks at the plugs so if the coil is good, the only other thing that can be wrong is the igniter module not giving proper voltages.
The igniter acts like a switch, connecting the coil (-) terminal to ground in order to charge the coil, then breaks the connection to fire the spark plug. If the igniter is 'on', charging the coil, it is carrying current to ground- multiply the resistance of the coil by 12v to arrive at the Amperes it is delivering. Without the airflow driving gives it, and the off periods where it's not grounding the coil, it will overheat and degrade.
This degradation means that instead of connecting the coil (-) to ground, "ground" will slowly become 1v, 2v, 4v, 8v ... above ground, and that means less current in the coil and a weaker spark.
The igniter acts like a switch, connecting the coil (-) terminal to ground in order to charge the coil, then breaks the connection to fire the spark plug. If the igniter is 'on', charging the coil, it is carrying current to ground- multiply the resistance of the coil by 12v to arrive at the Amperes it is delivering. Without the airflow driving gives it, and the off periods where it's not grounding the coil, it will overheat and degrade.
This degradation means that instead of connecting the coil (-) to ground, "ground" will slowly become 1v, 2v, 4v, 8v ... above ground, and that means less current in the coil and a weaker spark.
09-21-2013, 11:59 AM
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09-21-2013, 05:04 PM
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Generally, no, a coil will not test okay with an ohm meter and be bad. The voltage across it, and the resistance in the coil is what generates the high voltages to create sparks at the plugs so if the coil is good, the only other thing that can be wrong is the igniter module not giving proper voltages.
The igniter acts like a switch, connecting the coil (-) terminal to ground in order to charge the coil, then breaks the connection to fire the spark plug. If the igniter is 'on', charging the coil, it is carrying current to ground- multiply the resistance of the coil by 12v to arrive at the Amperes it is delivering. Without the airflow driving gives it, and the off periods where it's not grounding the coil, it will overheat and degrade.
This degradation means that instead of connecting the coil (-) to ground, "ground" will slowly become 1v, 2v, 4v, 8v ... above ground, and that means less current in the coil and a weaker spark.
The igniter acts like a switch, connecting the coil (-) terminal to ground in order to charge the coil, then breaks the connection to fire the spark plug. If the igniter is 'on', charging the coil, it is carrying current to ground- multiply the resistance of the coil by 12v to arrive at the Amperes it is delivering. Without the airflow driving gives it, and the off periods where it's not grounding the coil, it will overheat and degrade.
This degradation means that instead of connecting the coil (-) to ground, "ground" will slowly become 1v, 2v, 4v, 8v ... above ground, and that means less current in the coil and a weaker spark.
Just fantastic posting. Makes me cry a little...
Okay, you're scaring me. 
10-01-2013, 01:17 PM
#37
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Unfortunately not yet. I installed the new ignitor, but it still won't start. I tried another coil (used), but the results are the same. The distributor air flow meter check out okay with an ohm meter. Dang
10-01-2013, 05:19 PM
#39
I'm still leaning toward a "flooded" condition.
Hook-up a jump box to the battery and or another source to aid your trucks battery in excessive cranking time, and try to clear out the engine VIA "cranking and throttle application several times."
It may take several attempts.
Hook-up a jump box to the battery and or another source to aid your trucks battery in excessive cranking time, and try to clear out the engine VIA "cranking and throttle application several times."
It may take several attempts.
10-02-2013, 12:43 AM
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Yellow spark, different coil, different igniter, cranks at 'normal' speed.
Spark should be bluish, and if the coil tests okay, and a substitute performs the same, that leaves the igniter not delivering proper voltage (or rather ground) to the coil... and if that doesn't work...?
I'm seriously at a loss here.
Spark should be bluish, and if the coil tests okay, and a substitute performs the same, that leaves the igniter not delivering proper voltage (or rather ground) to the coil... and if that doesn't work...?
I'm seriously at a loss here.
