1989 Johnson 70 doesn't always start easily after running and idles rough

[racerone]

Look up the fuel pump for a 65 hp " commercial " model 3 cylinder and install that !!

 

[sumocomputers]

OK, so got my Stevens DVA, coil extenders, and the resistance load pigtail. All I can say is it is effen awesome to have the right tools for the job.

Anyhow, I went through all the various ignition system tests: Running Output (failed), Charge Coil (passed), Sensor Coil (passed). It led me through the process to the final step, which was the Power Pack test (failed). All 3 outputs were 190V, and should be 230V, so I am going to get a new power pack with relative confidence that this actually needs replacing.

However, I decided for fun to do the Stator and Rectifier test, which is in a totally different section under the "Charging System".

The Rectifier had some really weird readings, which I am still trying analyze. The manual is pretty vague on what is "high" and "low" reading, but I know it charges the battery when running, so I am not too worried about this right now.

BUT, the Stator test shows 1.7 Ohms, and the manual says it should be 1.3 Ohms +/- 0.1 Ohm, pretty clear it is out of spec.

I really don't look forward to replacing the Stator with the associated cost of $250+ and having to remove the flywheel (I think).

So questions: Am I risking anything by replacing the Power Pack and not the Stator? Is there a way for the Stator to be "kind of" out of spec, but good enough for now?

And most importantly, can a faulty Power Pack like mine contribute to the rough idle issue?

 

[Bosunsmate]

powerpacks going sick cause all sorts of faults so, yes
Stator i wouldnt be too concerned by a little bit over ohmns wise but did you test its cranking output thats what really matters
Also a broken rectifier can on some motors stuff things up so give that some more looking into as well

 

[sumocomputers]

According the service manual, it vaguely states:

"A very high reading in one direction and a low reading in the other direction, indicates the diode is OK. Two high readings or two low readings indicate that diode is damaged."

Based on this, I am pretty sure the rectifier is not within spec, so may have to look at replacing it too. I am assuming a typical good reading would be maybe something under 1 KOhm and the reverse would maybe be something above 1 MOhm, but have no idea.

Here are the rectifier readings:

Between Red & Yellow 125 KOhm (Positive Lead on Red)
BetweenRed & Yellow 63 KOhm (Negative Lead on Red)

BetweenRed & Yellow/Gray 1.8 MOhm (Positive Lead on Red)
BetweenRed & Yellow/Gray 620 KOhm (Negative Lead on Red)

People say don't throw parts at the problem. I have been troubleshooting and testing correctly, and I am still having to throw parts at the problem! But almost every part I have replaced so far has been absolutely original, so I guess I should expect things to fail after 26 years!

 

[Bosunsmate]

i havent done one for a while but i think my low readings were under 1 ohmn

 

[Bosunsmate]

People say don't throw parts at the problem. I have been troubleshooting and testing correctly, and I am still having to throw parts at the problem! But almost every part I have replaced so far has been absolutely original, so I guess I should expect things to fail after 26 years!

yes although if you hook the battery cables up the wrong way it will cut its lifespan down to a few millisecs

 

[sumocomputers]

So after meticulously following the ignition system troubleshooting from the service manual, it told me I had a bad power pack based on low voltage output directly from the power pack of only 190V (supposed to be 230V). I also had found the rectifier was bad.

So I installed a new rectifier and a power pack today, and son of a...I am still getting lower than expected voltage output. I only checked the running output test, which before was putting out 215-220V (should be 250V), now it's even worse at only 195V on all 3.

But the engine still starts and runs and jumps 7/16" on the gap tester.

The replacement power pack is a Sierra branded unit made by Mallory (made in Germany). I suppose it could be a bad power pack out of the box, but I am afraid that might be wishful thinking.

For fun I measured the resistance of the all 3 of the Sierra branded spark plug wires that appear in very good condition, and I get 190/190/170 Ohm. The manual indicates they should be near zero, but maybe these are a newer type? Have no idea if this is a problem to pursue or not, but it still won't change the low output voltage from the power pack issue.

Do you have any wisdom on where I should go next? I don't mind ponying up for a new stator if that seems likely, but feel I need to get more clarity this time before I throw another part at this problem. Note that as part of the charging test, the stator shows 1.7 Ohm instead of 1.3 +/- .01 indicated in the manual.

Thanks,

Chris

 

[sumocomputers]

Just for fun, here is a video running at idle with the new power pack and rectifier.

Also took out the NGKs and put in the exact Champions (gapped at .030) listed in the service manual.

No real change from before...

https://youtu.be/lV1VcuPJaXg

 

[racerone]

Are you saying that with all these new parts and work it is still not running properly ???

 

[sumocomputers]

Are you saying that with all these new parts and work it is still not running properly ???

That's what I'm saying.

I posted a video because I got to thinking that maybe someone will come along and tell me "Hey Chris, that's how they're supposed to idle!"

But seriously, I would like to get the ignition output tests to be within spec, otherwise, how can I eliminate the ignition system as a culprit?

 

[AlTn]

google...ISSUU.com/cdielectronics/docs/troubleshootingguide....pages 40-43...