B90TLRX, anything but the CDI?

[bkurth922]

First let me say I wanted to avoid having to ask this here. I’ve spent a good bit of time troubleshooting, as well as reading and rereading previous posts as not to waste anyone’s time.Closest I can find is http://www.yamahaoutboardparts.com/f...97-yamaha-80hp But as much as I love solving puzzles, I'm stumped so here goes, I’ll start with the symptoms.

Yamaha 2 stroke 1999 B90TLRX 3 cylinder on a Hewes Bonefisher.

The engine starts up normally, maybe a little slower than in the past. Idles out of the launch ramp (about 100 yards) a little rough but not out of the realm of normal for a two-stroke. Here comes the fun part. Make it out of the no wake and go to throttle up and ….. blah. Won’t get on plane and only makes it up to 2200 rpms with the throttle all the way forward. Will spin up all the way to the top if I rev in neutral, and will also increase rpm if I turn her all the way over and the prop starts cavitating. So I do what any normal person would do and go fish the shoreline nearby for 15 minutes. Go to leave and all the sudden we are back up and running perfectly normal for the rest of the day. However… it seems the wait period for normalcy has been getting longer. (Sidenote it seems to happen when it is cold outside, had a day in the upper 70s a couple weeks ago and no problem).

Flash to today, same problem, so I thought I would try to isolate which cylinder wasn’t working. Pull the airbox and get up to the blazing 2200 rpms and, all the carbs are spraying fuel into the carb throats, and when I place a rag over the throats the middle carb (#2) causes no effect. Of course while idling back to the ramp in the wind and cold she suddenly decided to get up and run… arghh.

Now I’m not gonna leave you there to try and explain my issues, here is everything I have troubleshot.

Compression- all between 100-115

Used the service manual -

Testing spark gap jump (9mm), sometimes all three work, sometimes (temperature?) #2 has no spark.

Have switched the leads from the CDI to coils, always the #2 lead from CDI without spark.

CDI Unit output - @1500RPMS - #1 ~150 #2 0 #3 ~150

Charge coil? Haven’t got to that one yet but shouldn’t be an issue since #1 and #3 are firing perfectly.

Pulser coil output in spec – 280 ohms ~9volts DVA open circuit

Crank position sensor – 199ohms, >5.5 volts DVA on startup

Timing and linkages checked and adjusted to spec.

Tried running with pink (overheat/oil alarm) disconnected. No difference.

Have not tested the Thermo switch.

Replaced or fixed

New spark plugs NGK B8HS-10

New spark plug boots

Replaced #2 ignition coil

All grounds and connections pulled, cleaned, and retightened.

Carbs taken apart, cleaned (in carb dip can + sprayable carb cleaner + pressurized air), and rebuilt with rebuild kit ( orings, gaskets, needle, seat, etc.). I Also don’t think this is the issue since I watched fuel getting through each carb throat while running today.

New fuel pump

New thermostat

Cleaned fuel filter inside cowling. Also running 10 micron Yamaha filter + non ethanol fuel.



Basically I’m looking for any other ideas about why the #2 spark plug isn’t firing and getting juice from the CDI before I bite the bullet on the 600$ part that is the least likely part to fail from everything that I have read

[99yam40]

need to be testing crank position output and all other inputs to CDI when problem is there to rule them out.
if all inputs are good into the CDI when output is bad the it could be inside the CDI

I am thinking that motor has only 2 pulser coils so the CDI makes up #2 output using CPS

[walleye1]

CPS fires #2

[bkurth922]

All the values above were when the no spark problem was occurring. So CPS output is in spec. Will retry again today to confirm. As well as running with the spark tester while wiggling every wire and connection to see if I’m losing it there.

[robert graham]

The limp mode could be actuated by oiling system or overheat.....sounds like limp mode??

[bkurth922]

And it won't stop raining so no testing yet today, hoping to get a break in the rain soon. If not today then tomorrow morning for sure.

To the limp mode idea, its a good idea and i ran down that rabbit hole - No alarms (alarm definitely works for low oil), and it is my understanding that limp mode causes a retardation of the timing, resulting in lowered RPMS. It does not get rid of spark in one cylinder across all rpm ranges.

[panasonic]

From reading what you said that this happens when the engine/weather is cold and then once the engine warms, running on 2 cylinders.... it then starts firing #2 and off you go with no problems.

That's sounds like a bad connection that once it warms up starts to work again. Seeing that #2 is the culprit and it gets it signal from the CPS I would be looking at the connections between it and the CDI.

Perhaps it is the CDI acting up when its cold, but not likely, you could test this by warming up the CDI with a hair dryer while the engine is cold and see if it then runs on all cylinders while the engine is warming up.

[bkurth922]

Panasonic - that is a great idea. On the list for tomorrow. The bad connection also makes sense now that I'm thinking about it - the last time I was out for a full day and it got to the running fine point, it would have split second losses of power when I hit a big chop then go right back to normal. Interesting, very interesting.

Also, just got a break in the rain and ran outside. Only got a chance to test the CPS but after all my reading and yall's help seems the likely culprit. Retested and got 3.3v while cranking open with the kill switch pulled and 10-12v @ 1500. Spec says at least 5.5v at cranking and 25v @1500rpms. I guess a connection check and possibly replacement CPS is in order.

Just because I have to know, other than being a 20 year old engine, what might cause this part to fail. Just want to make sure that nothing upstream (i.e. stator) is actually causing the issue.

[bkurth922]

Appreciate all input. Pulled the CPS, base was super corroded and figure it got to the internals/wire/and or connectors causing the faulty connections. Replaced and problem solved. Have a good one.

[99yam40]

thanks for dropping back in to let all know what fixed it.
I wish everyone would do that

[holmen78]

Appreciate all input. Pulled the CPS, base was super corroded and figure it got to the internals/wire/and or connectors causing the faulty connections. Replaced and problem solved. Have a good one.

Thanks for replying with the solution. I have done this myself(90TLRA) and I don’t understand why it is a dash in SM for cyl2 when testing peak output from CDI. I got about 130 DVA from all outputs when cranking (connected). I remember from this forum someone said that CPS gives signal to cyl2. That’s confirmed.

[holmen78]

Why would it have a dash? It's should still have an output for #2....cdi is just getting input from cps.

If you have opened up the attached picture in post #11 there is a dash for cyl2 in CDI output specs. And it hurts my head when I don’t know why .

Im not surprised though, I have found several things in SM that are wrong.