Yamaha 90 2 Stroke No Spark

FloatingBy

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Hi all, I've seen a few other threads about this which didn't quite match my scenario so I thought I'd post my own in the hope of some diagnostic suggestions.

I have a 2010 Yamaha 90A (AETO). It has no spark. Was running perfectly and just shut down, wouldn't restart. I am no boat engineer but have some tools and service manual (not all of which makes sense to me, being honest!).

I have seen advice about cleaning 'contacts' under flywheel. But from what I have been told, the only 'contacts' under there are not contacts, just magnetic pick ups, and sealed in a resin casing so dirt/oil shouldn't prevent them functioning.

The only import detail is that we found a broken earth, one coming from the communal earth on the wiring cradle. We replaced the wire (corroded) with a good new circle connector so that's fixed. I hoped that would be the cure, but it wasn't, still no spark after doing that.

One very weird detail - We disconnected the crank sensor, put meter probes into the sensor male pins just to see what voltage was doing when cranking engine. It not just sparked but fired into life! As if that isn't weird enough (I wouldn't think it can run without crank sensor connected to CDI), we plugged it back in and it fired up again!

Then today there's no spark again. All plugs are good and clean, and battery is very good.

Any suggestions would be appreciated at this point, as can't afford to take it to the dealer right now, and kids have fish to catch :)

thanks for any ideas
 

FloatingBy

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Would be very grateful for any replies here. Things have 'progressed' a little, no solution yet but I tested all the components (pulser coil, lighting coil etc) both for resistance and voltage when cranking. I will post the results below in case anyone knowledgeable sees anything useful in these results, cos I don't! I hope I am not heading towards needing a CDI as that could mean my boating days are over :(

CDI output - when cranking (assuming I tested correctly, think so but can't be sure as book doesn't make it idiot-proof!)

#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)

If anyone can determine any ideas/suggestions from those values, I am all ears! Thanks
 

99yam40

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need a peak voltage reading meter made to test these CDI systems
or a DVA adapter and regular meter set on DCv

look up CDI electronics trouble shooting guide on line to see if reading that helps you understand some of the stuff in your manual

the key switch turned to off and/or the man overboard lanyard pulled off kill switch ground the output of the CDI to stop spark fro reaching the spark plugs
 

FloatingBy

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Thanks. I only did the CDI readings because I thought I might as well, wasn't sure about it anyway. The main point was the other readings, all those coils.

I had a guy rebuild the carbs for me a few years ago, he's been a Yamaha approved repair agent for 30+ years so he knows his stuff. I assumed it could be faulty engine stop switch or key switch. I have confirmed 100% it's not the engine stop switch. I mentioned that I wondered if a faulty key switch could be to blame but he said no, if the engine cranks (which it does) then that switch shouldn't be causing no spark. I wonder if he's wrong about that? I hope not, he seems to know his stuff.

He said I would need to take it to him for proper diagnosis, but he's a long way from me and booked up for weeks/months :(

I was hoping someone might be able to confirm some of my coil readings were good or bad, and lead me in some direction towards something to try replacing!
 

99yam40

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might try looking here


if not the switches then maybe the wiring has a intermittent grounding of the wire that kills the spark

I have never tried taking AC voltage readings ,so I have no idea how that would compare to specs
 

FloatingBy

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Anyone know if there's an experienced Yamaha engineer who would take a look at my readings and give me some advice (paid of course)?
 

99yam40

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I have a feeling they would tell you to use the proper test equipment to take readings or take the motor to someone that could
 

FloatingBy

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They may well do. To which I would reply "Sadly impossible, so can my readings be assessed and a guess made as to what I could take a stab at replacing first". My Fluke meter measures resistance and voltages accurately, any knowledgeable person will know enough from my readings to make some sort of comment, which is all I am after at this point, in the absence of anything else.
 

99yam40

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re reading yu posts, all I can think of is you have a bad connection somewhere or a short to ground on the kill wire, kill switch or key switch.
there are no 2010 2 strokes here ,so not much we can look at

seems you moved something around that caused the spark to show back up.
I would be checking around there
 
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FloatingBy

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Thanks, I appreciate you trying to help. Those things have all been checked and ruled out. I am sure I have read posts on this board in the past about this engine, from what sounded like very knowledgeable people. But they could have been 10+ years ago now! Ho hum, worth a shot. thanks again
 

QBhoy

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Hi. Some cdi models have a tps too. Has yours ? Alternatively I’m also aware that some also have a shift switch that cuts ignition when coming out of gear. This is under the gear assembly in the lower cowl. I think you can also bypass the cdi and sensors altogether, putting the system into a fixed timing get you home type mode. Have you tried that ? Something about yellow wires on the cdi or disconnecting them or similar
 

FloatingBy

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Struggled to follow any of that! Let's start with.. what's a TPS?! Certainly sounds like some ideas to look into,.
thanks
 

QBhoy

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Struggled to follow any of that! Let's start with.. what's a TPS?! Certainly sounds like some ideas to look into,.
thanks
Throttle position sensor. It’s at the front of the engine. Wee moving sensor that is linked to and measures the opening degree of the butterfly or throttle body intake..that then sends a signal to the cdi to control the timing and ignition to suit the running conditions optimally.
Not sure if yours has one. But I know the larger v6 2 stroke (some of them) with cdi units certainly do.
 

FloatingBy

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Thanks, that's a good shout! I don't think I have seen one mentioned in the service manual but will do another careful check. I also heard there's a neutral sensor in control box that can prevent starting if stick isn't in neutral. I am pretty sure that wouldn't allow the solenoid to kick the starter over, rather than just preventing spark, but will double check.

Things have progressed a little, thanks to 99Yam40's reply above. I spent hours learning and realise a mistake i made, my readings were taken in AC using a standard digital fluke meter. I now understand I need a DVA adapter both for peak readings (rather than RMS) and to convert it back to a DC reading, in order to compare those properly to book values.

But I am also reliably informed by a decent electrical guy I know, that the only 'proper' way is to test the resistance of all the relevant coils. Having now found the correct values, and comparing to mine, it looks to me (albeit an untrained eye) that the CHARGING COIL looks to be the prime suspect.

I am told the two main causes of the spark, are the pulser coil (which triggers WHEN to spark) and the charging coil (which sends correct voltage to CDI, to pass on to ignition coils).

The book says the pulser coil resistance should be between 241-362 ohms. Mine reads 309, so that looks ok I think.

The charging coil though, which consists of two coils, both tested separately, should have:

Coil 1 - 64-96 ohms
Coil 2 - 191-288 ohms.

For Coil 1 I get a reading of 12 or 13 ohms, for Coil 2 I get 200. So looks like Coil 1 could be the problem.

It's scary making decisions like this (especially having seen price of these components and fell off my chair!)
 

QBhoy

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Thanks, that's a good shout! I don't think I have seen one mentioned in the service manual but will do another careful check. I also heard there's a neutral sensor in control box that can prevent starting if stick isn't in neutral. I am pretty sure that wouldn't allow the solenoid to kick the starter over, rather than just preventing spark, but will double check.

Things have progressed a little, thanks to 99Yam40's reply above. I spent hours learning and realise a mistake i made, my readings were taken in AC using a standard digital fluke meter. I now understand I need a DVA adapter both for peak readings (rather than RMS) and to convert it back to a DC reading, in order to compare those properly to book values.

But I am also reliably informed by a decent electrical guy I know, that the only 'proper' way is to test the resistance of all the relevant coils. Having now found the correct values, and comparing to mine, it looks to me (albeit an untrained eye) that the CHARGING COIL looks to be the prime suspect.

I am told the two main causes of the spark, are the pulser coil (which triggers WHEN to spark) and the charging coil (which sends correct voltage to CDI, to pass on to ignition coils).

The book says the pulser coil resistance should be between 241-362 ohms. Mine reads 309, so that looks ok I think.

The charging coil though, which consists of two coils, both tested separately, should have:

Coil 1 - 64-96 ohms
Coil 2 - 191-288 ohms.

For Coil 1 I get a reading of 12 or 13 ohms, for Coil 2 I get 200. So looks like Coil 1 could be the problem.

It's scary making decisions like this (especially having seen price of these components and fell off my chair!)
Could be onto something there. Not sure I mentioned, but some later (certainly larger and maybe yours. Not sure) had a shift switch that cuts ignition to a couple of cylinders (usually) or half the cylinder on an even number of cylinders otherwise…when coming out of gear. It’s situated usually under the gear actuator assembly in the lower cowl. Just a micros switch that’s contacted with the coming out of gear. Worth a look. But sounds like you might be onto a culprit for sure
 

FloatingBy

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Thanks. Never heard of that switch, don't think mine has one but will double check. Any idea what the technical term would be? Would make researching it easier. Mine is a 2010 so if they ever did put those on the Yam 90A 2 stroke, I'd expect mine to have it
 

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QBhoy

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Thanks. Never heard of that switch, don't think mine has one but will double check. Any idea what the technical term would be? Would make researching it easier. Mine is a 2010 so if they ever did put those on the Yam 90A 2 stroke, I'd expect mine to have it
Shift switch it’s called I’m sure. Shift interrupt on other models perhaps.
 

boscoe99

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Neutral Safety Switch - In the control box. To prevent a motor from being started in gear.

Shift Cut Switch - On some motors. Causes a motor to misfire some cylinders to assist in shifting the motor from in gear to neutral.

Shift Position Switch - On some motors. Tells the brains of the motor if the lower unit is in gear or out of gear.
 

boscoe99

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A 90 HP Yamaha two stroke does not have a shift cut switch or a shift position switch.
 

boscoe99

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A 90 HP Yamaha two stroke does not have a TPS. Throttle Position Sensor.
 
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