Ignition Coil Test Results

[bjcsc]

Trying to help a friend diagnose a no spark on a 1997 Johnson 115 EUA. We have not built a DVA and are testing what we can without it first. The engine ran great for several outings and then would not restart when shut off. Went through all the basics on the water, wiring/connectors, main breaker, shut-off. When testing the ignition coils, we get the spec'd resistance on the secondaries, but not on the primaries. We're getting about .4 - .5 Ω and the spec is .1 ? .05 Ω. We're also getting continuity from the primary to ground. Bad coils?

 

[racerone]

One coil could fail I suppose but not all 4 of them.

 

[bjcsc]

Yeah, that's what we thought, too...just can't figure out why we're not seeing what the manual says we should be on them...

 

[gm280]

You can't take reading to ground if the coils are still connected up. You have to isolate the primary side from ground and then read the resistance. Because if they are in the circuit, the low resistance will always read to ground. That is how they are wired into the ignition circuit. So remove the coil and read the resistance on both primary and secondary before you condemn them... And then if you want to see if the coil is compromised, test the coils windings to the coil metal assembly. If you read resistance then, the coil is bad. JMHO!

 

[jakedaawg]

Get an open air gap spark tester. If you find you have no spark on all cylinders Find the five pin amphenol connector. Jump all the wires across except the blk/yel. If you now have spark your problem is in the key switch/kill circuit or in the wiring.

 

[whalenj]

You can't take reading to ground if the coils are still connected up. You have to isolate the primary side from ground and then read the resistance. Because if they are in the circuit, the low resistance will always read to ground. That is how they are wired into the ignition circuit. So remove the coil and read the resistance on both primary and secondary before you condemn them... And then if you want to see if the coil is compromised, test the coils windings to the coil metal assembly. If you read resistance then, the coil is bad. JMHO!

Thank You!

 

[Fed]

Safety lanyard in place?

 

[Chris1956]

The spec for the primary ign coil resistance is .05 - .15 ohm. Some ohmmeters are not accurate enough to measure that, versus a dead short. Secondary winding is 225 - 325 ohms.

I once had a cheap Radio Shack multimeter that could not tell the difference between 400 ohms and a dead short That meter went to the dumpster, after I figured it out.

 

[Fed]

Probably shorting out the meter leads would give you 0.3 - 0.4 Ohms.

 

[bjcsc]

Thanks all. Checked the coils as instructed and they are in spec. Roger that on the cheap meters Chris1956, I have no time for them - I use a Fluke 117. I borrowed a DVA from a friend who owns a marine service business and everything checked out OK except the powerpack. We're replacing that tomorrow, provided someone has it in stock, and will post results here...

 

[gm280]

Thanks all. Checked the coils as instructed and they are in spec. Roger that on the cheap meters Chris1956, I have no time for them - I use a Fluke 117. I borrowed a DVA from a friend who owns a marine service business and everything checked out OK except the powerpack. We're replacing that tomorrow, provided someone has it in stock, and will post results here...

Great to hear you have it figured out. And I second the cheap meter junk as well. Cheap meters are not setup to be very low resistance measurement meters but more general info type meters. However the Fluke you used is a great meter for such... If you ever want a great analog meter, look for a Simpson 360 series. Probably one of the best analog meters even built. If you are dealing with coil and transformer winding resistances, you have to be able to get extremely low and accurate resistance measurements...

 

[bjcsc]

Well I wish I could say we figured it out, but we haven't. We replaced the powerpack with a new Johnson part (from the dealer) and nothing changed. We ran through all the tests again and again it pointed to the powerpack. Every component tests to spec per both the factory manual and the CDI guide, including the sensor. We are at the shop now, but have no idea where to go from here...

 

[jakedaawg]

Did you do the test where you jump all the wires except for the bulk/yel at the 5 pin am phenol connector? First step, very important.

 

[bjcsc]

Not sure where that connector is, but we ran all the tests that eliminated the kill switch. Also checked blk/yellow for ground - yes when ignition off, no when on or starting. We also hooked up a remote starter, did all the key switch tests, stator, rectifier, all of it...all the wires going into the powerpack tested in spec as described in the tests, both DVA and resistance...but still no voltage on the primary leads...very puzzling. Could the timing sensor be bad but still show the correct voltages as spec'd in the tests?

 

[bjcsc]

After reading through several threads posting similar problems, and with nothing really left for us to check/do, we are replacing the optical sensor today. Will post results...

 

[bjcsc]

Good news! Replacing the timing sensor fixed the no spark problem - super strong lightning across 7/16 gap on the tester. For the archives, the old sensor tested in spec per the factory manual and the CDI troubleshooting (Or/Red 10.5-12V DC and Blk/Or 8-10V DC). If I was doing this over again, and all the voltage, resistance and DVA results singled out the powerpack and sensor like they did for us, and even if the sensor tested in spec, I would replace the sensor ($90). If that didn't fix it, I would then replace the powerpack ($322). Thanks everyone for your help...

 

[AlTn]

thanks for taking the time to post all your results as this will surely assist others in the future

 

[bjcsc]

Definitely. I never leave threads hanging...there are enough of those already... BTW, the engine started immediately and ran like a sewing machine