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31 August 2023, 00:11
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#1
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Yamaha 90A 2 Stroke - Anyone knowledgeable on coils?!
Hi all,
I have a terrible intermittent 'no spark' issue. It can literally be sparking one minute and not the next.
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 will paste them below, I am desperately hoping someone knows a lot more than me about these engines, and might be able to comment on whether anything can be learned from this data?
Thanks
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)
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31 August 2023, 07:41
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#2
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Member
Country: UK - Scotland
Town: Easdale
Boat name: Miss Isle
Make: Solent 6.9
Length: 6m +
Engine: 225 optimax
Join Date: Jan 2008
Posts: 1,427
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Can’t interpret your readings without a manual but I’d suspect coil if the readings are not the same.
However start simple. It’s electrical when did you last change the battery?
Are the leads tight?
If it’s intermittent first place is check all connections. After that check battery leads for breaking down. After that you are likely into a failed component eg coil breaking down
Hope that helps some
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I was born not knowing and have had only a little time to change that here and there.
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31 August 2023, 13:12
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#3
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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They are all coils!
All simple stuff has been ruled out. Rock solid battery, soldered connections, clean terminals tight etc etc. Also ruled out kill switch and all the other usual suspects. I think we are down to components.
I have today managed to find resistance readings in the manual, didn't see them before but managed to make my keyboard make an OHMS SUMBOL in a digital search of the service manual, and hey presto, YAY!
Here is a direct link to page 28 (2-8) of the manual which shows all the correct resistances, time to start studying!
I found out last night how much these components cost, hundreds even just for a pi55y little pulser coil, so I have to check and check and check, can't afford to 'guess buy'!
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31 August 2023, 22:13
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#4
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Member
Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 70hp + aux
MMSI: 235087213
Join Date: Jun 2007
Posts: 4,607
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Just a thought, I assume the remote has start in gear protection? There should be a little microswitch in there. Relatively inexpensive and potentially could be the issue.
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01 September 2023, 06:31
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#5
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Member
Country: UK - Scotland
Town: Fort William
Make: Ribcraft 585
Length: 5m +
Engine: Yamaha F115
Join Date: Mar 2012
Posts: 2,913
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Quote:
Originally Posted by spartacus
Just a thought, I assume the remote has start in gear protection? There should be a little microswitch in there. Relatively inexpensive and potentially could be the issue.
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That shouldn’t cause it to cut out whilst running.
I had a similar issue with a Honda and it turned out to be the CDI unit throwing a hissy for no apparent reason.
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There is a place on this planet for all of Gods creatures.........right next to my tatties and gravy.
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01 September 2023, 07:50
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#6
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Member
Country: UK - Scotland
Town: Easdale
Boat name: Miss Isle
Make: Solent 6.9
Length: 6m +
Engine: 225 optimax
Join Date: Jan 2008
Posts: 1,427
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When it cut out could you tell if you lost all cylinders? If it sounded like any cylinder was trying to fire check ignition coils.
If there was nothing check neutral and kill switch
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I was born not knowing and have had only a little time to change that here and there.
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01 September 2023, 12:46
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#7
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Thanks all, some good suggestions there. To answer:
When it cut out I am certain it was all three, no sparks on any cylinder. I am sure ignition coils are fine. I have learned a lot in past few days, hours of watching Dangar Marine type videos and reading threads on here and elsewhere. Was worth the time in long run I think, just hate being out on water and not really understanding my own engine. (even though "2 strokes don't go wrong", hahaha)
PROGRESS...:
CDI unit, Pulser Coil and Charging Coil are the three most likely suspects here.
CDI unit I can't test properly (i now know) until I get my DVA adapter (hopefully today). But I can test resistances of the pulser coil and the (2 coils inside the) Charging Coil.
Pulser book says should be 241-362 ohms. My reading is 309 so looks ok to me.
Charging coil - one coil should be 191-288 ohms and mine reads 200, good. But the other coil in it should be between 64-96 ohms, but mine reads 12 or 13 ohms.
Do we have a prime suspect?!
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01 September 2023, 13:05
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#8
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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With an intermittent fault I dont think the readings are very meaningful unless the fault is occurring at the time. I'm assuming the engine now starts & runs okay? Unless you can recreate the fault it will be difficult to pinpoint with any degree of accuracy.
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01 September 2023, 13:07
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#9
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Thanks, that's a very good point.
It is failing now. No spark.
I bought a set of Laser spark plug lighter upper thingermejiggies off Scamazon. Those are staying connected so I shuold see some lights flashing if I do get a spark back. But no spark currently. Would be nice to see a spark so I could test while it is working but the Gods aren't shining on me on that score at the mo
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01 September 2023, 13:57
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#10
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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Quote:
Originally Posted by markS
Thanks, that's a very good point.
It is failing now. No spark.
I bought a set of Laser spark plug lighter upper thingermejiggies off Scamazon. Those are staying connected so I shuold see some lights flashing if I do get a spark back. But no spark currently. Would be nice to see a spark so I could test while it is working but the Gods aren't shining on me on that score at the mo
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Got a cdi here that lost a cylinder if you want to try it, obviously if it runs on two cylinders you know its the cdi. The fact you have a complete failure is a good thing usually easier to fix than an intermittent fault
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01 September 2023, 14:11
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#11
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Wow, what a generous offer, that's extremely kind of you. I am hoping it isn't the CDI, but having that available would get rid of the need for "hope"!
So your one is faulty but has a known fault (only runs 2 cylinders). So if i swap mine out to that, and I get 2 cylinders running, my CDI is bad. Sounds like a great thing to have on the bench to try amongst the various other tests! Would you like to PM me to sort that so I can send you postage money etc?
PS - No, the problem I have appears to be VERY intermittent! It's just that it's in "bad mode" right now. I could go turn the key this afternoon and it could be sparking again! It's a nightmare! I have bought the spark plug tester lights so I can hopefully noticed if/when it sparks again, maybe it won't, maybe it will!
The trouble with this stuff is, everyone seems to say "well it can't be that because it's intermittent and that would just fail" about EVERY component I mention, CDI, pulser coil, charging coil.... all of em! Some people say "Never known a CDI to go wrong" which is as useful as a chocolate fireguard, even more so if i DO have a bad CDI!! So I have given up guessing and gathering amateur opinions (mine included ![big grin](https://www.rib.net/forum/images/smilies/biggrin.gif) ). It's now down to testing every component.
I can't test the CDI until tomorrow as the DVA didn't arrive today as hoped. But it would be very interesting to have a spare CDI I could test the outputs of, to compare to mine. Just to rule out my own testing equipment/process. If yours reads as per book (on 2), and mine doesn't, I would have more faith in my readings before taking out a mortgage for a new CDI!
Thanks again, very kind of you.
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01 September 2023, 17:42
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#12
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Member
Country: USA
Town: NorCal
Boat name: SHARKY
Make: AB
Length: 4m +
Engine: Honda BF75 & BF5
Join Date: Dec 2009
Posts: 2,053
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You would need a lab scope for more thorough testing. About all you can do is check inputs, and grounds, as there isn't much you can do for testing a "black box" itself. Using a replacement unit is about the only way. The tap and wiggle test is a valid test LOL
Have you taken an ohm's reading for the coils themselves?
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01 September 2023, 18:10
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#13
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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Is it the same? ![Click image for larger version
Name: 20230901_190904.jpg
Views: 76
Size: 42.7 KB
ID: 143507](https://www.rib.net/forum/attachment.php?attachmentid=143507&thumb=1&d=1693591817)
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01 September 2023, 19:57
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#14
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Quote:
Originally Posted by Peter_C
You would need a lab scope for more thorough testing. About all you can do is check inputs, and grounds, as there isn't much you can do for testing a "black box" itself. Using a replacement unit is about the only way. The tap and wiggle test is a valid test LOL
Have you taken an ohm's reading for the coils themselves?
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haha. Not sure i took resistance reading for coils, kind of ignoring them as i either have 3 sparks or none, but i will get readings tomorrow and post back. thanks
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01 September 2023, 19:58
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#15
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Quote:
Originally Posted by beamishken
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Certainly looks the same, incliuding wire colours, but not sure if that is reliable enough. I have never removed one (bit scary for me!) so I guess i need to remove it to check numbers on the back? Or maybe I can research it using diagrams online. My engine is 2010 model:
ha, i posted image but it's not showing for some reason. Its here: https://ibb.co/qsL4QtZ
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01 September 2023, 20:05
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#16
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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Theres nothing to be scared of removing one just pop off the timing rod & unplug the wires i think the 6ho in the plastic moulding is the relevant no if yours matches that then I think your okay
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01 September 2023, 20:06
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#17
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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I see. Thanks, Will have a bash tomorrow.
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01 September 2023, 20:20
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#18
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Member
Country: UK - Scotland
Town: north ayrshire
Boat name: charlie girl
Make: S/R5.4/regal3760
Length: 10m +
Engine: Suzukidf70 2x6lp 315
Join Date: Jul 2009
Posts: 3,927
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Quote:
Originally Posted by markS
I see. Thanks, Will have a bash tomorrow. ![smilie](https://www.rib.net/forum/images/smilies/smile.gif)
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Should be able to see the no with it insitu but it may have a cable cover you'll need to remove to see it that one is mega expensive £500 ish but a 6h2 one which fits the 60/70 is available as a copy for about£80 looks almost identical too
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02 September 2023, 05:39
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#19
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Member
Country: USA
Town: NorCal
Boat name: SHARKY
Make: AB
Length: 4m +
Engine: Honda BF75 & BF5
Join Date: Dec 2009
Posts: 2,053
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Quote:
Originally Posted by markS
haha. Not sure i took resistance reading for coils, kind of ignoring them as i either have 3 sparks or none, but i will get readings tomorrow and post back. thanks
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Part of testing the coils is also testing their wiring. The coils could be considered the output side of the circuit. Test the input side of the circuit, and if all good replace the module. Then cross your fingers when you hit the key.
Complete failure of a component is far better than chasing an intermittent problem.
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03 September 2023, 12:10
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#20
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Member
Country: UK - England
Length: 6m +
Engine: Yam 90A 2 Stroke
Join Date: Aug 2023
Posts: 17
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Quote:
Originally Posted by Peter_C
Part of testing the coils is also testing their wiring. The coils could be considered the output side of the circuit. Test the input side of the circuit, and if all good replace the module. Then cross your fingers when you hit the key.
Complete failure of a component is far better than chasing an intermittent problem.
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Thanks. I assume you mean the pulser/charge coils, not ignition coils, as those have been ruled out. I am not sure how to test the input side of those connectors, any tips?!
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