Yamaha 150TXRB no spark on 1-3-5 cylinders and we're on vacation!

[joelisajer]

Thanks for all the help everyone. The stator came today and fixed the problem.

99Yam- I was using a fluke meter with peak hold. And I was using DC not AC as previously stated. Funny thing is that the charge Coils did test good resistance and got 177/55 volts for the high and low speed. I did not get a chance to try the loaded test. In retrospect that probably would have revealed the erroneous positive results. Though banking on the symptoms I was led to believe that the charge Coils could not cause this problem.....

After seeing everything working, I went back in and reinstalled the original pulser, CDI, and cps. All is well. I'm going to try to megger the old stator and see if there is a bad connection within.

Bottom line is that a bad charge coil did somehow cause me to lose spark on 1-3-5. I'll let you experts debate on how that's possible. Boscoe was the only one that gave a plausible explanation. Thanks for that!


Many thanks to all for the input.

Joe

[99yam40]

good to hear it is going again.
But do get a DVA adapter for next time you want to take peak voltage readings. It will give you something to compare to the spec in manual .
what you get with that meter alone is not something that can be compared to specs

[boscoe99]

A magnet under the flywheel wizzes by the charge coil. It creates voltage in the charge coil when it does. However, the polarity of the voltage changes as the magnet approaches the coil versus when the magnet is leaving the coil.

As the magnet approaches the coil, induced voltage is fed to one capacitor. This capacitor is used to fire cylinders on one side of the motor.

As the magnet leaves the coil, induced voltage is fed to a different capacitor. This capacitor is used to fire cylinders on the other side of the motor.

So, if the circuit that is supplying voltage to the two capacitors fails in a manner that only one of the two capacitors gets its voltage then guess what? Only the cylinders on one side of the motor will get the voltage needed to fire the respective plugs.

Some Yams work this way and some don't. Some Yams use pulser coils only to fire cylinders. Some Yams use pulser coils and a crank position sensor to fire cylinders.

Pity the poor mechanic who has to know and understand about a million different combinations of Yamaha models. Shame on Yamaha for not providing the theory of operation in each service manual for the specific model that is being covered by that service manual. Mechanics waste their times and customers money. Makes for a less satisfied customer.

For some reason, when the motor was done Yamaha was done. They apparently don't give much thought or consideration when it comes to the data needed to support continued use of the motor.

[Z-man228]

Can someone expl what the DVA adapter is and where to get one if needed?

[99yam40]

see if reading this will answer your questions and do a search on the adapter they name
Print Out This Guide, The Use of Electronic Test Equipment for Outboard Motors.

[boscoe99]

Can someone expl what the DVA adapter is and where to get one if needed?

Think of the voltage in your home. It is based on alternating current. The voltage is constantly varying between zero voltage and some higher positive voltage and then between zero and some negative voltage. It does this 60 times a second.

When measured with a typical AC voltmeter you might see 120 volts indicated. However, in reality the actual maximum voltage is much higher. About 177 volts as I recall. Think of 120 volts as being the average voltage, although in reality it is not.

A DVA (peak voltage adapter), when installed on a voltmeter, will allow you to see whatever the peak voltage happens to be. In the case of your house, you plug it into the 120 volt receptacle and you will see 177 volts.

Some devices need to be tested at normal AC voltage and some need to be tested at peak voltage.

[Z-man228]

Thansk Boscoe

I have not encountered a need for that yet but knowledge for the future.

[rodbolt17]

most meters read WVDC or RMS both are the same just different words.
typically its 70% of the peak voltage.
the reason CDI or ADI, same just different words, ign systems need PEAK voltage is due to how fast the capacitors discharge into the ign coil.

old battery point type and later transitor controle ignition systems(TCI), have 12V on the coil primary all the time and rely on the contacts opening or the transistor turning off to stop primary current and cause the coil primary magnetic field to collapse.

CDI ign systems rely on the rapid discharge of the DC current stored in the capacitor to build and collapse the field.

that capacitor stores the rectified current the charge coil provides.

the pulser simply turns ON an SCR,it is called a gate signal.

once turned ON the SCR stays on until current flow drops below the SCR's threshold.
then the SCR turns OFF and waits until the next gate signal.

on the 150TXRB the low speed charge coil supplies operating voltage for BOTH banks.
one bank uses one leg of the two wire coil the other bank uses the other leg.

short one leg and lose one bank.
open 1 leg and lose BOTH banks.
the high speed charge coil does about the same thing but is used at speeds above about 2500 RPM.
later EFI motors and the 3.1L v6 DO NOT use a high and low speed coil system.
they use 2 charge coils dedicated to port and stbd banks.

that's why Boscoe had told the original poster to test for shorts to ground.

ANY time you are dealing with a two wire coil its imperative to test each leg for a short to ground.

while testing output voltages had the original poster tested brown to red he would have seen operating voltage.
then he quit.
almost tested it.

from there he should have gone brown to ground and red to ground.
the above test would have shown voltage on one leg and not the other if a leg was grounded.

or simply tested resistance brown to ground and red to ground.
this test would have shown open circuit on one leg (good)and closed circuit on the other(bad).
it all goes back to a fundament fact that to generate an AC current all you have to do is pass a magnetic field passed a wire.
you can move the coil past a stationary field or move the field past the stationary coil.