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Anyone know how many volts should be going to my Ignition Coil?

Pbdy Jr

Pbdy Jr

Member
I have a regulator wire traveling to the choke, and the other wire travelling to the starter slave solenoid. With the Ignition turned on, i get twelve volts through these wires. If i crank the motor, it drops to 9 volts. However, these readings are with the power unhooked from the coil. When i hook these wires back up to the coil, they read just over 5 volts. these wires heat up pretty quickly and I have no spark coming from the coil.. I am going to replace the coil, but I want to make sure this voltage is behaving as it is supposed to.

IMAG0591.jpg
 
Take regulator wire off coil. The wire going to choke should be purple, which comes from key , with 12 volts to choke.
If you are saying reg is hook to coil, it is acting as a big resistance.
But you never said if points or electronic ignition.... If points is your coil have on it external or internal reistance ....
plus what make is motor

Steve
 
It is a mercruiser 3.7 points system (for now) i have a purple going to choke and purple/yellow to solenoid. I get no spark from coil and have ordered a replacement coil. I am just hoping the wiring isnt gonna fry the new one. external resistor required however mercruiser says they use a resistor wire (purple/yellow i assume)
 
Pbdy Jr said:
It is a mercruiser 3.7 points system (for now) i have a purple going to choke and purple/yellow to solenoid. I get no spark from coil and have ordered a replacement coil. I am just hoping the wiring isnt gonna fry the new one. external resistor required however mercruiser says they use a resistor wire (purple/yellow i assume)
Click to expand...

Do this 1st clean points with sand paper.
Then take clean white paper , and pull paper though points 2 or 3 times.
I. Bet you will get spark back.
If still no spark unhook tach and try again.
I have seen tachometer take down spark.

Steve
 
Marine tech 57;422973]Do this 1st clean points with sand paper.
Then take clean white paper , and pull paper though points 2 or 3 times.
I. Bet you will get spark back.
If still no spark unhook tach and try again.
I have seen tachometer take down spark.

Steve[/QUOTE]

Cleaned the points again... Nothing. Detached wiring from the tach, nothing. How do go about the process of elimination
 
when you are cranking motor do you have battery voltage at plus side of coil.... If not take a jumper wire to bat plus side and coil plus side , see if spark comes back.
This motor you have you don't get coil go down to much. In 39 years never had one go down.
Things i found points not making good contact, bad condensor, wire going into dist cap shorting out, shift switch shorting out, kill switch bad.
The purple wire coming from starter, it's job is when cranking engine it gives you full battery voltage to coil for starting.Once motor starts resistance wire takes over from key. When did this problem start, and how

Steve
 
I just look back at your write-up. You state when cranking you go down to 9 volts, not wright. If you are taking the reading from plus side of coil, it must be battery voltage. If you are seeing 9 volts from dash, check cond of your battery under load, or put on charger. You should only have gray and black wires on neg side of coil

Steve
 
My battery is new and fully charged. I get just over a 12v reading. The wiring going into the coil + reads just under 12. As soon as i hook it up to the + of the coil, it drops down. This is partly why Im thinking maybe coil issue. I really appreciate ur suggestions. Here are some pictures of what I am working with

IMAG0588.jpgIMAG0599.jpgIMAG0606.jpg
 
Try this unplug wire harness.Then get yourself a starter button .Hook to yellow /red wire and the other to 12 volts.Then take a jumper wire put to 12 vote and postive side of coil.
Now crank engine and see if you have spark.
Just because you charge battery ,doesn't mean battery is good .You need to load test Battery could be your problem if you have a short in a cell.Make sure your shift switch isn'nt taking your volts to ground.
 
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