failed stator cause 78 140 johnson

[petersbc]

I had my 78 Johnson 140 out on the stand today to test run it after a whole bunch of work. The motor ran a year ago when I bought it but needed the power head gasket changed and some maintenance work done. The motor started sputtered, died and would not start. Subsequent troubleshooting showed no spark. Resistance check in the Stator shows out of speck and I get 0 volts DVA to either ignition pack connector with the packs unplugged. Is this just a fluke or could there be some other issue that caused this?

I have no idea how the motor ran under load as I bought it with a junk boat and never ran it under load. The way it ran on the muffs made me feel it needed carbs cleaned and when I looked at the plugs they were not colored uniformly (suspected carbs as well) For all I know the stator had issues and was limping along when it finally gave up the ghost this morning. At 225 for a replacement I'd like to guard another failure.

 

[boobie]

Sounds like a bad stator.

 

[Bosunsmate]

Check that the wires from the stator havent corroded and a shorting to ground

 

[petersbc]

no shorts verified that. Stator appears to be bad just wasn't sure if there was something that caused it to fail other than age. From what I understand it's just a pair of coils, for the ignition circuits, so ti should be pretty robust not like the electronics in the ignition packs.

 

[Bosunsmate]

Yes its might of done 36 years so is more robust than most things made in 78

 

[emdsapmgr]

When cranking, the stator should put out minimum of 150 volts at both A,B connectors or it is condemned. When checking cranking voltages with a peak-reading voltmeter, also check the timer base output voltages. Should be in the 0.3 to 0.6 volt range. Depends on year. Check out this website: cdielectronics.com

 

[Fed]

Resistance check in the Stator shows out of speck and I get 0 volts DVA to either ignition pack connector with the packs unplugged.

There's something about your results that doesn't seem right to me are you sure you're testing it properly?
2 open circuited coils (infinity)?
2 short circuited coils (0 Ohms)?

 

[V153]

Sounds like a bad stator.

I tend to agree. NO spark is a strong clue. Barring bad connections. Stators do go bad.

$225 sounds a lil steep. I'd shop around.

 

[tblshur]

petersbc , did you try disconnecting the black and yellow wires at power pack?:joyous:

 

[F_R]

Did you do a resistance check on the stator? I don't know, but I suspect there is a problem with your test procedure.

 

[gm280]

Understand how stators actually work, the only way I can see a stator being bad is if it shorts to ground or other windings or opens from corrosion. Other then that what else can a coil of wire do? And before I'd spent $200 dollars on a replacement, I'd unwind the actual wire until I found the problem myself. But I am just that way! I mean it is nothing but varnished bare copper wire.... :facepalm:

 

[V153]

I mean it is nothing but varnished bare copper wire

True. But in this case I'll bet it's encased in epoxy. Like so:

 

[Bosunsmate]

True. But in this case I'll bet it's encased in epoxy. Like so:

one guy on here recently managed to remove the epoxy from powerpacks, ive forgotten how he did it but it was really simple and very impressive.
i think he used some kind of chemical, a Russian guy i think

 

[V153]

one guy on here recently managed to remove the epoxy from powerpacks, ive forgotten how he did it but it was really simple and very impressive.
i think he used some kind of chemical, a Russian guy i think

Leave it up to the Russians ...

But seriously. Interesting. Reckon everything has it's solvent?

I member my Dad always hated chit encased in epoxy. Cuz he was so good with electronics he could've probly fixed it otherwise.

Sadly I did not inherit that gene ...

 

[Bosunsmate]

Leave it up to the Russians ...

But seriously. Interesting. Reckon everything has it's solvent?

I member my Dad always hated chit encased in epoxy. Cuz he was so good with electronics he could've probly fixed it otherwise.

Sadly I did not inherit that gene ...

Yes i wish i had bookmarked that page, it would of saved me twice as much as i have from comments on here already.
Il have a look later on and see if i can track it down but i dont like my chances after a quick search just now

It was quite amazing what he did, the circuit board came away nice and clean and he just replaced a $1 capacitor and away he went,
I think the biggest difficulty was deciding whether to protect it again in epoxy or not

 

[V153]

Purty cool. Like to know what kinda solvent he used.

I spose every chemical reaction has an opposite reaction?

 

[gm280]

He could of used Aircraft Remover being how it does attack epoxies and such. But who really knows. My stator coil is merely wire wound on the metal frame. That is why I stated I would unwind it to find the problem.

 

[petersbc]

I jut got the socket in today to pull the flywheel so I hope to get that done tonight. As far as testing goes I used the procedure in the CDI manual. Resistance is lower than spec at ~320 ohms but not a dead short and it's infinity to ground. That is on both outputs. Voltage readings were taken with the stator completely disconnected including the charge leads just for good measure. I was surprised at no voltage. Made me think my DVA was not working but I tested it on a running 70 and it works fine.

I'll do a visual tonight as the windings do appear to be shorted somewhere and that would could cause the no voltage issue I still want to see the damage if possible. Hopefully the epoxy will be burnt and I wont have to dig further. Found replacement stators for as low as 189 new (CDI) and found a couple on ebay for less that were replaced and found not to be the problem so they are being sold as used. That all boils down to trusting the seller though. .

 

[petersbc]

Pulled the flywheel and it's definitely an original part. Looks a little crispy around the coils that drive the CDI but that may just be wishful thinking. Bought a replacement stator that is supposed to be here tomorrow. Not sure if I'll get the chance to install it and test the motor again this weekend but I'll update when I do just to close the loop.

 

[Fed]

Still not making a lot of sense, did you zero the ohm meter before testing?