No spark on #3 cylinder on 1999 90hp 2 stroke

[relic hunter]

I need help with a no spark issue on my 1999 90hp. I have used my repair manual to trouble shoot a problem with the ignition system on my engine. A little background. The problem has been intermittent, until now. I am getting no fire on the #3 (bottom) cylinder. At first it seemed that the problem would develop when the engine warmed up, however, now it occurs immediately after starting.

I have switched out the coil and put in a new plug so I know thats not the issue. Following my repair manual I have tested the pulser coil resistance and found it within the limits at 326, the crankshaft position sensor and found it within range at 217, and the ignition charge coin and again found it within range at 80 and 248.

I had two failures, the ignition charge coil output failed at cranking speed, 11 volts, 1500 rpm .. 50 volts, and 3500 rpm .. 54 volts. The pulser coil output test failed at all three intervals as well, showing very low voltage, less than 2 volts.

** note ** I performed the tests with the boat hanging in the sling, as well as out on the water under a load. Results were basically the same.

Reading the manual it would seem that both my ignition charge coil and pulser coil are bad.

My question, which I have not been able to find the answer to in the manual, does one system affect the other. In other words, are both coils bad, or is only one bad, which in turn causes the other to fail the test. I guess I find it hard to believe that both coils have gone bad at once. Or is there something I am missing in my reading of my manual?

Thanks in advance for any assistance.

[rodbolt17]

did you test each leg of each coil for shorts to ground?
the CPS only affects cyl 2.
the pulser coil triggers 1&3.

did you run the output voltage tests both loaded and unloaded?

[99yam40]

what are you using to test voltage with?

Special peak reading voltmeter made for these ignition systems is needed
or a DVA adapter with regular meter will work.

How did you test that #3 was not firing?

If there is spark but not firing ,it probably has to do with fuel. maybe fuel pump as #3 crankcase is where pump gets its pulse from

[relic hunter]

After spending more time on various repair forums I read about DVA. My manual did not explain using it, rather it used the term common meter set at the highest AC voltage scale. So, that being said, I guess my reading were all incorrect. I believe my meter came with the adapter, I just have to find it.

I don't believe its fuel related. I initially rebuilt the carbs, because of the way it performed. Started and ran great, fell down under load, never reaching full RPM. After doing so it ran great, and then the same issue once the engine ran for a while. I removed the silencer, and ran it at WOT. I can see fuel spraying out of all three carbs, exactly the same. Removing the bottom plug shows that it is fouled. To eliminate ignition coil/plug issue I moved the bottom coil to the top and top to the bottom and put in a new plug. Still the bottom cylinder doesn't seem to be firing. I say that ... I remove the plug wire and observe no change in the rpm, whereas when I remove the other two I observed a noticeable drop in rpm. My spark tester broke and I haven't been able to purchase a new one to test the presence/strength of any spark.

Any suggestions will be truly appreciated. Im fairly mechanical inclined, however, this is my first attempt at 2 cycle outboards. I am retired with time on my hands so I figured it would see if I could fix it before taking it to a shop.

[99yam40]

If the fuel pump leaks fuel into the #3 crankcase it will run too rich on that cylinder and spark will not ignite it.

remove the bolts holding it to motor but do not remove the fuel lines .
with it off pump the primer bulb and see if fuel comes out of the pulse port.

Or take it apart and inspect the parts for problems.

Any automotive part store should have spark testers.
Timing light hooked to the different plug wires should show if there is spark on them also.

Just because you pulled and cleaned the carbs before does not mean they did not plug up again with something that was hiding in the lines and pump once going.

compression is always something good to check when having problems just to be sure all are sealing

[relic hunter]

I had read about the fuel pump possibly being an issue so I rebuilt it. But I did not test it for leaks, so that will be my first task today.

I will also put a timing light on the #3 cylinder and see if Im getting spark that way.

It appears, from the reading, that the coils would not cause me to only lose one cylinder. Am I correct on that?

I haven't done a compression test yet. That too was on my list. I will be going in to town later this week and will borrow a compression tester from a local automotive store.

Regarding fuel, delivery doesn't seem to be an issue. Observing the carb throats at WOT all seem to be spraying fuel the same.

I will be back with results.

[relic hunter]

Update ..

First let me make sure I am correct about cylinder numbering .. is the top cylinder the #1 cylinder. I want to make sure my coils are plugged in correctly.

I tested the fuel pump .. no leaks observed .. pulse port nice and dry ..

I removed the bottom plug, reattached it to the coil and left it laying in the engine well. I started the engine and observed a bright blue spark(s) at the plug. Lesson learned, I should not have assumed because I unplugged the spark plug and observed no rpm drop that it wasn't firing.

I put the plug back in and removed the silencer cover. I ran the boat on the water and observed that gas was being sprayed into the throat of each carb, in what appears to be equal amounts.

I placed my hand over the top carb .. good vacuum felt .. engine died.

I placed my hand over the middle carb .. good vacuum felt ..engine died.

I placed my hand over the bottom carb .. vacuum felt less than the other two .. no affect on the engine .. it continued to run ..

I returned to the dock and removed the bottom plug .. it was wet with fuel .. not fouled black and oily .. but slightly wet .. I dried it .. attached to the coil and left it in the well and started the motor .. again observed bright blue spark(s) ..

I guess I need to do a compression test next ..

Question .. could I have a reed valve problem .. and how can I test

[relic hunter]

Finally did a compression test .. 0 on the problem cylinder ..

Time to start from scratch

[TownsendsFJR1300]

If you have a leak down tester, it may help diagnose a blown head gasket/leaking/broke rings, but in any case, the head is coming off.

0 compression is obviously not good.

Looking thru the spark plug hole, can you see the top of the piston(specifially, any holes)?

It may be a corroded head but building 0 compression, it should be pretty obvious...

http://www.boats.net/parts/search/Ya...ASE/parts.html

Please post what you find...