Need Thinking Caps

[Capt Ken]

OK, I know I'm suppose to be the guru of Yamaha Sterndrives but I've got a YEMS that is stumping me. So I thought I would bounce some stuff around here and maybe someone will come up with something I haven't thought of.
YEMS, not firing. Came from another shop that probably couldn't spell Yamaha. They replaced the ignition switch and kill switch and wired some stuff up wrong. Owner said it started and ran for a few seconds and died.
Checked voltage and have 12 volts to igniter (computer) Checked ground to igniter and its good. Unplugged the pickup assembly (dist module) plugged in another module, spun it by hand and coils fired. OK, must be bad module so I replaced the module with the test one, buttoned everything back up. Tried again and still no spark. Took the old module, plugged it back in, spun it by hand and the coils sparked.
Now the only difference I can see with the modules I'm testing with is they are not bolted in and grounded. But if ground is needed, why are they working not grounded. If the igniter is faulty, then why is it working with the module out of the engine? By it firing when I spin the module, that tells me everything is operational. Oh yes, I did remove the cap of the module and made sure it was spinning as the engine turns over.
Y'all throw something at me and make me think outside the box.

 

[Don S]

Re: Need Thinking Caps

I'd sure like to help you Ken, cause you've sure helped a lot of others. But I don't have a clue what YEMS even is. I worked for a Yamaha dealer a couple years ago, but didn't even see a Yamaha IO, let alone a YEMS, only outboards (and he wasn't even a dealer for a full year before he lost it).

 

[blouderback]

Re: Need Thinking Caps

Yamaha Engine Management System.

 

[Don S]

Re: Need Thinking Caps

Yamaha Engine Management System.

Thanks, but I was referring more to how it works and what parts are in the system than what the letters stand for.

 

[Bondo]

Re: Need Thinking Caps

Thanks, but I was referring more to how it works and what parts are in the system than what the letters stand for.

Ayuh,.... Ditto here,... I've never even seen 1....

 

[Capt Ken]

Re: Need Thinking Caps

Actually only three components. Computer that is called the igniter. Coils (which there are two so rare that both would fail). Then third is the module that takes the place of the distributor and tells the igniter when to fire the coils.
So the question would be, why does the CPS fire the igniter while in hand and spinning it, but doesn't fire it when bolted in. All the other whistle and bells just influence timing depending on conditions.
Did scare some folks. When I first spun the CPS by hand, I guess there was fuel in one cylinder that had an open exhaust valve and it lit off with a big bang.

 

[Maclin]

Re: Need Thinking Caps

Not sure what all that looks like, but maybe the case or some other component of the CPS is cracked or warped or minutely damaged, and when bolted in it shorts out or breaks some connection.

I had a car buddy, primo troubleshooter, other dealers of other make cars would wait in line at the dealership where he worked. One car was a BMW, had a sensor that counted crank revolution intervals by "reading" a toothed wheel on the crank and one or 2 teeth were broken, probably happened at the factory. He spent 2 hours diagnosing, then told them what part to replace and that did fix it. That car had been a yo-yo all it's short 6 month life at that time, back to BMW even.

I will see if he is out of jail yet on that cocaine charge, sigh...

 

[Capt Ken]

Re: Need Thinking Caps

The CPS actually looks like a distrubutor but with the top cut off. I would think something with the CPS except I have two of them and both act the same way. I may swap out the igniter later today and see if that makes a difference. Really isn't like there is a lot of parts to the system and thank goodness I have spares to test with.

 

[Capt Ken]

Re: Need Thinking Caps

The son gave me an idea. The other factor is, when I'm spinning the CPS by hand, I'm not cranking on the engine so the igniter is getting a full 12 volts. When I spin the engine, the voltage on the ignition wire to the igniter drops to 9 volts. I will need to check that out. He thinks that maybe the voltage is dropping too much to power the igniter.

 

[lexer440]

Re: Need Thinking Caps

Maybe the CPS shouldn't be grounded, but insulated?

 

[fishrdan]

Re: Need Thinking Caps

When I spin the engine, the voltage on the ignition wire to the igniter drops to 9 volts.

That definitely sounds suspect, I could see 9V shutting down the ignition.

If that's not the problem and you are wondering if grounding the CPS is shutting down the ignition, ground it out with a jumper wire when it's off the engine, then give it a spin by hand.

 

[500dollar744ti]

Re: Need Thinking Caps

The son gave me an idea. The other factor is, when I'm spinning the CPS by hand, I'm not cranking on the engine so the igniter is getting a full 12 volts. When I spin the engine, the voltage on the ignition wire to the igniter drops to 9 volts. I will need to check that out. He thinks that maybe the voltage is dropping too much to power the igniter.

that is extremely probable. what kind of engine are we working with here? i'm assuming it's some kind of GM that's been bastardized by yamaha?

i'd really like to be there to look at is as this kind of diagnostic troubleshooting is my specialty. i don't know enough about the system to diagnose over the internet but if i was there i'm sure i could do it.

i am imagining this YEMS distributor looking like what they use on the newer jeep 4.0 strait-6. they converted that motor to coil on plug ignition and used what looks like a chopped off distributor to get a crank angle signal.

i need to know what engine it's on so i can jump on google, get a nice overview of the system and help out diagnosing it.

knowing yamaha, i think they would design a quality system using nice denso or bosch parts but these parts may be so scarce that it's worth changing so something more common.

if it were my boat, provided it's some kind of GM motor and the parts are too hard to find, i'd rip that stuff out and put mercruiser thunderbolt ignition on it and call it a day. i'm not much of points guy but you could do that too.

 

[Capt Ken]

Re: Need Thinking Caps

There is actually Denso labels on most of the components.
The CPS would have to be grounded in the grand scheme being its bolted down to the block.
I've had to move it back in line since another job is pressing. Customer just had a 1972 Whaler Montauk hull restored and I'm rigging it out with a new F90. I love starting with a clean slate except the first problem is, bow light wiring somehow got fiberglassed over and have no idea where it is. Guy that did the glass and paint just stuck the light on the front with wires hanging out.

 

[500dollar744ti]

Re: Need Thinking Caps

bow light wiring somehow got fiberglassed over and have no idea where it is.

ha, that's pretty funny, guess you are going to have to go chase wires from the switch.

i really like reading all these threads, i've been an auto mechanic for 10 years and now i really want to work on boats. i feel like it would be a nice change.

 

[Capt Ken]

Yamaha Still Amazes Me

Yamaha Still Amazes Me

For my last question on the YEMS that was baffling me, I woke up the other morning with the answer. Went into the shop, grabbed a used ECU off the shelf, swapped it out and the engine ran great. All I can think is somehow when the previous mechanic wired in an aftermarket key switch, he didnt know what to do with the extra wires so he stuck them to positive. Those wires where part of the kill circuit on the kill lanyard. That affected the ECU somehow where with the distributor module ungrounded, it worked but installed and grounded, it didn't.
Also, for many years the ECU was unavailable and no longer stocked. I checked and they are now in stock in Japan. $1400, but available.

 

[kfa4303]

Re: Yamaha Still Amazes Me

Re: Yamaha Still Amazes Me

sweet. Nothing like a little brain transplant to make things right. I've always heard really good things about Yamis. The old 2-strokes are fetching a pretty penny these days. Especially the 40-60 hp models that folks love running on their skiffs in our neck of the woods. I'd love a 2-stroke, tiller Yami 50hp for my boat, but I'll have to stick with the old Johnson 20 hp for now. Besides, I don't think my little boat could handle that much motor anyway, but maybe a 40 hp.....

 

[Bondo]

Re: Yamaha Still Amazes Me

Re: Yamaha Still Amazes Me

For my last question on the YEMS that was baffling me, I woke up the other morning with the answer. Went into the shop, grabbed a used ECU off the shelf, swapped it out and the engine ran great. All I can think is somehow when the previous mechanic wired in an aftermarket key switch, he didnt know what to do with the extra wires so he stuck them to positive. Those wires where part of the kill circuit on the kill lanyard. That affected the ECU somehow where with the distributor module ungrounded, it worked but installed and grounded, it didn't.
Also, for many years the ECU was unavailable and no longer stocked. I checked and they are now in stock in Japan. $1400, but available.

Ayuh,... Hope ya don't mind Ken, I combined yer threads, so the final answer is now with the original problem...

Glad ya figured it out....

 

[Capt Ken]

Re: Yamaha Still Amazes Me

Re: Yamaha Still Amazes Me

Thanks, I should have thought of that