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No voltage to coil while cranking

T

T4Turtle

New member
Picked up a 1985 Sea Sprite with a OMC 3.8 engine that has a Petronix converted electronic ignition. I have 8.5 volts to coil with key on and a weaker battery. During cranking the voltage at coil drops to zero volts. Also a purple wire and a red wire with a white tracer are hanging below the shifter. The purple wire has 10.5 volts key on and 12.5 key off. No voltage either way on red wire and not a good ground.

any help appreciated.
 
Also have 9.5 volts while cranking on purple wire off starter solenoid when disconnected from coil. If I connect the purple wire to coil then no voltage while cranking.
 
Also the open purple wire under shifter has continuity to the purple wire at starter solenoid and purple wire at coil. Not sure where this should connect to, thinking ignition switch. Ordered service manual off eBay.
 
There was an open terminal on ignition switch that said I GEN so I tried connecting the purple wire under shifter to it but now getting no voltage at all
 
in most cases the coil power during cranking comes from the solenoid at the starter. It should have 2 short studs. one has the yellow-red stripes inboard and the purple-black outboard
 
Last edited:
The typical starter motor amp draw is enough to lower the voltage to the coil, often preventing the coil from producing a good high voltage output (i.e., spark).
The cure for this was to incorporate what's called a "Start-by-pass" circuit.
The "Start-by-pass" circuit can originate from the starter motor solenoid's "R" or "I" terminal, and will circumvent any ignition system ballast resistor during cranking.

Some starter motor solenoids do not offer the R or I terminal, and will use a relay that is triggered by the S circuit (i.e., the yellow/red stripe wire circuit).



 
Bt Doctur said:
in most cases the coil power during cranking comes from the solenoid at the starter. It should have 2 short studs. one has the yellow-red stripes inboard and the purple-black outboard
Click to expand...

I have both wires and it is an inboard with the purple wire going to the coil.
 
Bt Doctur said:
in most cases the coil power during cranking comes from the solenoid at the starter. It should have 2 short studs. one has the yellow-red stripes inboard and the purple-black outboard
Click to expand...

If the purple wire is not connected to coil I have enough voltage, it is when I connect it to the coil I do not. Maybe a bad coil drawing too much?
 
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