OMC Engine Not Starting - No Spark from Coil

I have an 1986 Four Winns with an OMC 5.0 Chevy. Has the petronix electronic ignitor in the distributor. The other day I was adjusting the carb to get the idle set properly. The boat was starting and running great except a small idle issue.

I turned the boat off, made an adjustment to the throttle linkage at the carb, then the boat would not start. Pulled the coil wire off, and found it had no spark from the coil.

• I tried grounding directly from the coil without the wire, still nothing.
• Checked the voltage at the [+] side of the coil. Ranged from 4-7 volts voltage is the same at both coil terminals.
• I tried using 2 other coils I had (one from the shelf, one borrowed from another boat) all 3 showed the same symptoms.

I then found that when I removed the 2 grey wires from the [-] side of the coil, the voltage at the [+] side jumped up to 11 volts. Next, I disconnected the grey tach wire to check if that was grounding somewhere, still no change. This now means the voltage drops down when connecting the grey wire from the ESA.

I tried bypassing and disconnecting the ESA several different ways, and still could not get spark.

It doesn't seem like this voltage drop should be there. Any Ideas on what might be the cause of my issue? Bad ESA? Bad Ignitor?

Thanks!

Re: OMC Engine Not Starting - No Spark from Coil

gvsu141 said:

[*]Checked the voltage at the [+] side of the coil. Ranged from 4-7 volts voltage

Click to expand...

to properly check voltage to your coil, put the red meter lead on the coil +
put the black meter lead on the Battery negative, not the other post of the coil

If you have a fully charged battery and you get less than 8V there with key on , and less than 11.5 while cranking..start checking for bad wiring

never never never, check voltage across the coil + to - , that is meaningless

Re: OMC Engine Not Starting - No Spark from Coil

Howard Sterndrive said:

to properly check voltage to your coil, put the red meter lead on the coil +
put the black meter lead on the Battery negative, not the other post of the coil

If you have a fully charged battery and you get less than 8V there with key on , and less than 11.5 while cranking..start checking for bad wiring

never never never, check voltage across the coil + to - , that is meaningless

Click to expand...

Just to clarify: I checked the voltage at the [+] coil post by grounding my meter to the battery to get the low reading. I then checked the [-] coil post using the battery as a ground, and the volts matched.

Did you see later in the post where the volts jumped up to 11 after disconnecting the ESA from the [-] coil post?

Re: OMC Engine Not Starting - No Spark from Coil

Do you have a set of points you can throw in real quick?

Re: OMC Engine Not Starting - No Spark from Coil

gvsu141 said:

Just to clarify: I checked the voltage at the [+] coil post by grounding my meter to the battery to get the low reading.

Click to expand...

ok, then the diagnosis was done right at that moment.
if you only have 4 to 7 volts, with red meter lead on coil + and black meter lead on batt neg., that's why you have no spark. The coil is probably fine, but you can take the purple/red wire off the coil and check it to see if the voltage is any different when it is not connected to the coil. it probably will not change.
Fix the wiring to get 9.5 to 11 volts there with the key on. could be a loose or corroded connection or a burnt out resistance wire (purple/red) or even a faulty ignition switch in the dash.
You can disconnect the purple/red wire at both ends and check its resistance - should be 1.5 to 3 ohms.

Re: OMC Engine Not Starting - No Spark from Coil

did you check to see if the rotor is spinning?

Re: OMC Engine Not Starting - No Spark from Coil

Howard Sterndrive said:

ok, then the diagnosis was done right at that moment.
if you only have 4 to 7 volts, with red meter lead on coil + and black meter lead on batt neg., that's why you have no spark. The coil is probably fine, but you can take the purple/red wire off the coil and check it to see if the voltage is any different when it is not connected to the coil. it probably will not change.
Fix the wiring to get 9.5 to 11 volts there with the key on. could be a loose or corroded connection or a burnt out resistance wire (purple/red) or even a faulty ignition switch in the dash.
You can disconnect the purple/red wire at both ends and check its resistance - should be 1.5 to 3 ohms.

Click to expand...

When I discnnect the purple wire from the coil, that wire has 11 volts. When connected to the coil it only has 4-7. When the ESA is disconneced from the coil, the purple wire again goes up to 11 volts, but still no spark.

Re: OMC Engine Not Starting - No Spark from Coil

Levinz11 said:

Do you have a set of points you can throw in real quick?

Click to expand...

No, the ignitor was installed before I had the boat.

subcrx said:

did you check to see if the rotor is spinning?

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I did not check that, but now that I think about it when I held the coil wire with my bare hands checking for spark, I did feel a very weak "poke" but not as strong as it should be.

Re: OMC Engine Not Starting - No Spark from Coil

gvsu141 said:

When I discnnect the purple wire from the coil, that wire has 11 volts. When connected to the coil it only has 4-7. When the ESA is disconneced from the coil, the purple wire again goes up to 11 volts, but still no spark.

Click to expand...

it sounds like that wire supplying the coil has really poor conductivity. and the bad connection could be anywhere back to the key switch.
you get proper voltage (11V), but as soon as you ask it to carry ANY serious amount of current - to run the coil and/or the ESA module, it craps out.

That is what you would typically see in a wire like that when only 2or 3 of the tiny little strands are conducting instead of the 50 or 60 copper strands.
It only takes 1 copper strand in tact to show the 11V on a modern digital multimeter.

but it seems unlikely that that issue would suddenly pop up after a throttle adjustment.

Also, when you CRANK the engine, all of that circuit is bypassed anyways (full 12V comes from the starter post crank terminal to the coil +).... so I'm a bit surprised the symptom isn't that it "will fire as long as the starter is cranking, but quit once the key is released"
or is that the case?

Re: OMC Engine Not Starting - No Spark from Coil

Howard Sterndrive said:

but it seems unlikely that that issue would suddenly pop up after a throttle adjustment.

Also, when you CRANK the engine, all of that circuit is bypassed anyways (full 12V comes from the starter post crank terminal to the coil +).... so I'm a bit surprised the symptom isn't that it "will fire as long as the starter is cranking, but quit once the key is released"
or is that the case?

Click to expand...

I tried adjusting the throttle back for the heck of it, and no change.

I also tried providing 12v to the coil [+] directly from the battery via jumper wire, with no sucess in getting spark. I can't remember if I checked the volt reading with it jumpered or not.

Re: OMC Engine Not Starting - No Spark from Coil

Howard Sterndrive said:

so I'm a bit surprised the symptom isn't that it "will fire as long as the starter is cranking, but quit once the key is released"
or is that the case?

Click to expand...

It doesn't fire at all, even when cranking the engine.

Re: OMC Engine Not Starting - No Spark from Coil

Possibly a kill switch? Just wondering out loud

Re: OMC Engine Not Starting - No Spark from Coil

The problem must be in the distributor. You said you took it "apart". Something in there is not right. Take a closer look.

I get 8.5 volts at my coil + while running. That is within spec. 7-9 is what the book calls for. 12v while cranking.