Yamaha 90A 2 Stroke (2010) - Intermittent No Spark - Can anyone help?!

[MarkScott18]

Hi, I have read quite a few threads which have helped me a little with this problem, so I thought it might be wise to post the actual issue here in case someone can help.

I have a VERY intermittent 'no spark' issue. One minute it sparks, the next it doesn't.
Engine has been perfect for 10 years, then out on the water after 3 hours of chugging around it suddenly cut out and wouldn't restart.
It caused me and my kids to get stranded and towed in (thankfully) by a kind trawler! It was just turning dark when the failure happened, suffice to say it's not an experience I wish to repeat, so boat is grounded until resolved.

I have taken readings of the various relevant components (pulser coil, CDI, etc). But I am not too sure how to make sense of them as they don't correspond to the service manual I was using (trying my best to understand it!). The engine is mint, 2010 with under a hundred hours of use. All connections are spotless, no corrosion, and covered in a nice smear of vaseline as they have been for the past ten years of my ownership. It's had virtually no use with me until this year (no time, or no money, or both!)

I took readings of both the voltages (when cranking) and resistances of the various parts. I used a standard decent quality meter (Fluke), I don't have whatever the diagnostic tool is that's referred to in the manual.

I will past my readings below, desperately hoping someone might be able to comment on whether anything can be learned from the data. I'd love to hear any comments, at this point I am stumped and don't want to just start guessing/buying things (especially after seeing prices of them!)

CDI output - when cranking
#1 - 1.1 to 1.3Vac
#2 - 0 to 0.4Vac
#3 - 1.1 to 1.3Vac

Charge Coil
R-Br - 61Vac (12/13 Ohms)
R-L - 74Vac (200 Ohms)

Pulser Coil
0.7 to 1.1Vac (309 Ohms)

Lighting Coil
12.85Vac (1.2 Ohms (dropping))

Crank Sensor
2.65Vac (197 Ohms)


Does anything stand out? Is there something I should go for IF I were to choose something to buy to swap out and see?!
thanks

[panasonic]

Here is the link for a adapter for your meter to read peak volts from those components.

https://www.amazon.ca/Voltage-Readin...%2C1755&sr=8-2

[panasonic]

Go here and look up your engine for the readings you should be getting with DVA adapter.

https://www.cdielectronics.com

[MarkScott18]

Thanks very much for replying. After posting, I spent the next few hours learning something new, and pretty damn relevant! I can't just take readings with standard meter, either AC or DC! I need a DVA which I hadn't heard of before! I have ordered one and will get peak voltages as soon as it arrives.

Perhaps more importantly, I managed to find the readings in the service manual. Couldn't see before but a digital search for a Ω symbol did the trick. This link shows all the correct resistances for these components (in case anyone in future finds this thread asking for correct values) - https://www.manualslib.com/manual/10...page=29#manual

Obviously my problem is how intermittent this problem is, so any readings (voltage or resistance) may vary depending on whether it's sparking or not. So I have bought some spark plug lights so i will see them flash if plugs are sparking. Hopefully between those and the DVA adapter, I can keep fiddling/testing and find something useful. Having seen the price of these components (300 plus for just a pulser coil) I can't afford to buy anything without being as sure as possible that it's faulty, even then not sure I can afford any parts for a while.

But making a bit of progress now I have the values linked above to compare my readings with. Thanks again, will update if I get anywhere, and I'd welcome any further input from anyone on here.
Cheers

[MarkScott18]

Go here and look up your engine for the readings you should be getting with DVA adapter.

https://www.cdielectronics.com

Sorry, I don't understand. I went there and searched for my engine, found it. But it only offers parts, I don't see anywhere to get values

[99yam40]

Sorry, I don't understand. I went there and searched for my engine, found it. But it only offers parts, I don't see anywhere to get values

try this part of his web site

Technical Support | CDI Electronics

[boscoe99]

What is the complete engine ID? Begins with the number 6.

[boscoe99]

Hi, I have read quite a few threads which have helped me a little with this problem, so I thought it might be wise to post the actual issue here in case someone can help.

I have a VERY intermittent 'no spark' issue. One minute it sparks, the next it doesn't.
Engine has been perfect for 10 years, then out on the water after 3 hours of chugging around it suddenly cut out and wouldn't restart.
It caused me and my kids to get stranded and towed in (thankfully) by a kind trawler! It was just turning dark when the failure happened, suffice to say it's not an experience I wish to repeat, so boat is grounded until resolved.

I have taken readings of the various relevant components (pulser coil, CDI, etc). But I am not too sure how to make sense of them as they don't correspond to the service manual I was using (trying my best to understand it!). The engine is mint, 2010 with under a hundred hours of use. All connections are spotless, no corrosion, and covered in a nice smear of vaseline as they have been for the past ten years of my ownership. It's had virtually no use with me until this year (no time, or no money, or both!)

I took readings of both the voltages (when cranking) and resistances of the various parts. I used a standard decent quality meter (Fluke), I don't have whatever the diagnostic tool is that's referred to in the manual.

I will past my readings below, desperately hoping someone might be able to comment on whether anything can be learned from the data. I'd love to hear any comments, at this point I am stumped and don't want to just start guessing/buying things (especially after seeing prices of them!)

CDI output - when cranking
#1 - 1.1 to 1.3Vac
#2 - 0 to 0.4Vac
#3 - 1.1 to 1.3Vac

Charge Coil
R-Br - 61Vac (12/13 Ohms)
R-L - 74Vac (200 Ohms)

Pulser Coil
0.7 to 1.1Vac (309 Ohms)

Lighting Coil
12.85Vac (1.2 Ohms (dropping))

Crank Sensor
2.65Vac (197 Ohms)


Does anything stand out? Is there something I should go for IF I were to choose something to buy to swap out and see?!
thanks

Yamaha service manual voltages are peak voltages. You have measured and list RMS voltages. To covert from RMS to peak you multiply the RPM by 1.414.

Were your measurements taken with the components loaded or unloaded?

Your wire colours are not making sense.

The output voltages from the CDI to the ignition coils is not making sense. Very very low. Not surprised that there is no spark. It may be that the output is so quick that an RMS meter might not be able to adequately capture the voltage.

Forget the lighting coil. Has nothing to do with ignition.

[boscoe99]

Yamaha service manual voltages are peak voltages. You have measured and list RMS voltages. To covert from RMS to peak you multiply the RPM by 1.414.

Were your measurements taken with the components loaded or unloaded?

Your wire colours are not making sense.

The output voltages from the CDI to the ignition coils is not making sense. Very very low. Not surprised that there is no spark. It may be that the output is so quick that an RMS meter might not be able to adequately capture the voltage.

Forget the lighting coil. Has nothing to do with ignition.

[boscoe99]

[panasonic]

try this part of his web site

Technical Support | CDI Electronics

I never looked at the web site closely but it looks like you have to buy the troubleshooting manual now. Whereas in the past you could look up the values on the website for free. I am not sure about that though as it has been years since I used it last.

[99yam40]

I never looked at the web site closely but it looks like you have to buy the troubleshooting manual now. Whereas in the past you could look up the values on the website for free. I am not sure about that though as it has been years since I used it last.

yes that is true, but they do allow you to view some pages free,
I have no idea how many free pages you are allowed to see , as I too have not looked there in years

[MarkScott18]

I'm so sorry. Didn't see any email alerts of new posts, and I've missed some really generous help here. Here goes...

What is the complete engine ID? Begins with the number 6.

6H1 - my engine serial number badge is:

Screenshot 2023-08-31 at 16.08.05.png

[MarkScott18]

Yamaha service manual voltages are peak voltages. You have measured and list RMS voltages. To covert from RMS to peak you multiply the RPM by 1.414.

Were your measurements taken with the components loaded or unloaded?

Your wire colours are not making sense.

The output voltages from the CDI to the ignition coils is not making sense. Very very low. Not surprised that there is no spark. It may be that the output is so quick that an RMS meter might not be able to adequately capture the voltage.

Forget the lighting coil. Has nothing to do with ignition.

Thanks Boscoe.

I have a DVA adapter now (originally I didn't, and readings were terrible for reasons you explain!).
Wire colours - I am going directly from the book, HOWEVER... L = Blue in the book (see key for wire colour codes), BUT on some of the troubleshooting pages it uses the term Blue and B for blue, rather than L. I have tested exactly as per book. R-L means red to blue (charge coil 1) and R-Br = red to brown (charge coil 2).

Components "loaded or unloaded". Not sure what that means, sorry. But one thing I did also learn as well as the need for a DVA, is that the Yam service manual uses the words "open" and "connect" for most readings. I assumed (assumption being 'the mother of all F Ups', as an old friend used to say!) this related to key position. I now realise this relates to whether the connectors are plugged in or not! In my case, ALL readings are taken from wires when DISconnected. I didn't have meter probes small enough to slip inside the bullet connectors, but I do now, so will take more readings with them connected tomorrow.

Here's an update since receiving DVA adapter, and i will try to explain carefully and clearly, as I need to because the spark re-appeared during testing! ...


Engine stop switch has been ruled out by disconnecting it. Battery and supply cables are all good. Based on tests it looked to me like a faulty Pulser Coil or Charge Coil. So I took resistance readings. I am not sure if resistance values are the BEST way to test a component, since Yamaha advises checking peak voltages. My understanding (limited) is that resistance will check a coil is not damaged, more than voltage would. I stand to be corrected here, but anyway...

Pulser Coil tests 'good' (in range) - I get 316 ohms and book says it should be 241-362.

Charge Coil contains 2 coils. One reads 205 ohms (book says 191-288) so that looks good. But the other one was reading 12-13 ohms when I checked a few days ago. I checked again yesterday and got a surprise when it read 6000-8000 ohms?!

A bit later I noticed the engine began sparking again (have test lights fitted for that reason), so I quickly took resistance readings again to see how they compare when it’s sparking, i.e. when the fault is NOT present. I got a reading of 73 ohms on that same coil, WHEN sparking. Book says 64-96. So I have correct resistance when sparking, wildy wrong/varied readings when not sparking, so in my limited knowledge, I would guess the charge coil needs replacing, and today I was told you can't replace that, have to replace whole stator at huge cost

Grateful for any thoughts on the above, which is the situation as of today. Having just realised that "connect" means cables left connected during testing, I will perform DVA readings again tomorrow and hope for something closer to the values given in the book.

THANK YOU

[MarkScott18]

PS - Thanks for that picture of readings above. Almost same as the manual I am using, except for "loaded/unloaded" which i think is equivalent to my books "open/connect".
Here is a direct link to the page of the service manual showing all the specifications/values my engine should be reading: https://www.manualslib.com/manual/10...page=29#manual
(Mine is the 90, far right side of all tables)