Looking for advice (possible ignition issue)

[Wisakedjack]

Sprint time engine failed to start. After checking on the usual suspect I've found that the spark between coil lead from the distributor cap and the cylinder head was very weak. It was yellowish and I had to almost touch the head with the lead. My engine has EI module and 3 Ohm Petronix Flamethrower coil connected via a ballast resistor. I've done the following tests:

1. Checked voltage between coil contacts with ignition on: ~7V (which I understand is way low).

2. Removed ballast resistor. Now voltage between coil contacts is 10.6V, but the spark is still weak. When I cranked the engine voltage between coil contacts dropped to 5.5V(!!!).

3. Check coil resistance, which measured ~3.5 Ohm.

4. Replaced coil with a spare one (though I have no idea if it was good). Coil resistance is also about 3.5 Ohm, but no good spark.

5. Put original coil in and connected jumper wire between '+' coil terminal and battery cable on the starter solenoid. Wire from the ignition switch was disconnected. Still no good spark.

I would appreciate any advise on what else I could test or what is possibly wrong here. Can the coil be bad even if its resistance looks right? Its possible that both coils gone bad, but I kinda doubt it. Does it look like an issue with EI module?

Thank you in advance for any help and suggestions.

[JOHN COOKSON]

Are you sure the battery is fully charged and still good? What does the engine sound like when you crank it? Like a weak battery? Give us a voltage reading at the battery when you crank the engine.
Take the voltage readings to ground not the other coil terminal. Coil - is not a ground.
You can get the EI out of the picture temporally by disconnecting the wire from coil - inside the distributor and with the key on and the EI closed touch\remove it to ground while holding the lead from the center of the coil near ground (the engine) This will mimic the circuit make\break action of the EI. Keep at it until you get a decent spark from the coil.
Others will be along. More as I think of it.

TRUE GRIT

[Wisakedjack]

John, I think the battery is ok. I measured 12.3V on the terminals (I have a bank of two). They were charged before I put them back on the boat. The engine sounds ok when I crank it. Definitely not like the weak battery. I will try other things that you've suggested when I get back to the boat this weekend. Thanks for your suggestions.

[hanleyclifford]

John, I think the battery is ok. I measured 12.3V on the terminals (I have a bank of two). They were charged before I put them back on the boat. The engine sounds ok when I crank it. Definitely not like the weak battery. I will try other things that you've suggested when I get back to the boat this weekend. Thanks for your suggestions.

12.3 volts is not a charged battery. A charged battery at rest should show around 12.7 While cranking you should be showing around 10 volts.

[Wisakedjack]

I agree that 12.3V is not a fully charged battery, but it should be enough to turn the engine and produce strong spark. No? Or do you think my spark issues can just be caused by battery being somewhat low on charge? Thanks.

[hanleyclifford]

I agree that 12.3V is not a fully charged battery, but it should be enough to turn the engine and produce strong spark. No? Or do you think my spark issues can just be caused by battery being somewhat low on charge? Thanks.

The really important thing is voltage at coil+ during cranking. Below 9 volts the engine will not fire, though a weak spark may be observed. You may have a lot of resistance in the system which precludes starting with a battery at 12.3 volts. Try connecting your voltmeter red to coil positive and black to the engine block. Crank and observe the voltage.

[romantic comedy]

Take off the wire from the negative terminal of the coil

Hook up a 1 foot, or longer, wire with a bare end to the negative terminal of the coil.

Take the wire from the coil to the cap and pull it out from the cap. You will need to hold it 1/8 to 1/4 inch away from the block to check for spark.

turn on the ignition switch.

Take the wire from the negative of the coil and strike it the the engine block. Hold the coil center wire to check for spark.

You should get a good spark doing this.
--------
it sounds like you are not getting enough voltage to the coil. Maybe bad connections or a bad battery.

[ndutton]

I want to reinforce what others have said and add a comment of my own.

1. DO NOT attempt to measure voltage between the two small posts on the coil. Voltage is measured with the ignition on between the small coil + post and a good engine ground. Try and avoid painted surfaces for the ground point.
2. While you may think the batteries are good, your measured voltage suggests otherwise (like 30% SOC) and during cranking it will be dramatically lower. You should measure the coil input voltage again as described above during cranking for a meaningful number.
3. When was the last time your spark plug wires were replaced? If it has been a while they're probably due anyway and there's no downside in having new wires. After all, they deliver whatever spark you're producing so why not have the best delivery system you can?

Note to Admin:
I propose adding SOC - State of Charge - to the glossary.

[hanleyclifford]

I want to reinforce what others have said and add a comment of my own.

1. DO NOT attempt to measure voltage between the two small posts on the coil. Voltage is measured with the ignition on between the small coil + post and a good engine ground. Try and avoid painted surfaces for the ground point.
2. While you may think the batteries are good, your measured voltage suggests otherwise (like 30% SOC) and during cranking it will be dramatically lower. You should measure the coil input voltage again as described above during cranking for a meaningful number.
3. When was the last time your spark plug wires were replaced? If it has been a while they're probably due anyway and there's no downside in having new wires. After all, they deliver whatever spark you're producing so why not have the best delivery system you can?

Note to Admin:
I propose adding SOC - State of Charge - to the glossary.

Second the motion, with the proviso that SOC be defined as measurement taken 20 minutes after all chargers and loads have been disconnected.

[JOHN COOKSON]

Another + 1

While you may think the batteries are good, your measured voltage suggests otherwise (like 30% SOC) and during cranking it will be dramatically lower. You should measure the coil input voltage again as described above during cranking for a meaningful number.
.

If a pond (battery) holds X gallons of water (electricity) and is full it is at it's full capacity.
If the pond unknowingly silts in it and the capacity is reduced will still appear to be full. If a voltage measurement is taken on a failing battery it may appear to be OK even though the total electrical storage capacity is reduced.
Stress testing the battery will reveal this condition.
My advice to the OP is to:
(A) With the key in the ON position measure the voltage at coil + before the resistor. This will check the wiring, switch and so on before the coil.
(B) Then, as noted, check the voltage at coil + while cranking the engine.
Don't do anything further to the ignition system until you can get satisfactory voltages as noted above.

TRUE GRIT

[Wisakedjack]

Thanks to you all for the suggestions. I am going back to the boat this weekend and will report my findings.

[hanleyclifford]

If You Really Want to Know

what is going on with a battery, this is the correct tool to own - available at your local auto boutique:

[Administrator]

Note to Admin:
I propose adding SOC - State of Charge - to the glossary.

Done.

Bill

[romantic comedy]

Hanley, that is a great tool. I have almost that exact one. This week my wife's civic sounded a bit slow when starting. I got out the meter and checked the battery. The voltage was fine but it failed the load test.

Got a new battery right away.

[hanleyclifford]

Hanley, that is a great tool. I have almost that exact one. This week my wife's civic sounded a bit slow when starting. I got out the meter and checked the battery. The voltage was fine but it failed the load test.

Got a new battery right away.

Good item for cruisers to carry in the inventory. Batteries are cheap along the ICW - except when they are delivered to a lonely anchorage.