Yamaha 225hp 2str Crank Position Sensor test

FrenchFry · Nov 15, 2009

How can we check if the crank position sensor is working or not ? I have seen different posts about testing the CPS but not saying how, mine shows a correct impedance while engine is not running but it looks like there is almost no continuity while engine is running (very high impedance)

rodbolt · Nov 15, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

DVA meter and the correct service manual for the 225 in question.
we dont use impedance for ANY sensor tests on yamaha outboards. resistance is ok but we always prefer running output voltage tests.
yes there is a difference between impedance and resistance.
and you cannot do either test on an active circuit.

FrenchFry · Nov 15, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

Thanks for the answer, by impedance I meant resistance in fact, the motor is 1990 Yamaha 225hp 2 srt V6, I don't have the service manual and used some tests mentioned in the seloc manual.

I am a bit confused, what do you mean by "you cannot do either test on an active circuit", how to check voltage output on an non active circuit ? For the tests I made, the cpt was disconnected, maybe absurd test but I find it strange that when flywheel is running the sensor shows very high resistance.

What do you suggest to do, at lease to check if it's dead or not ?

rodbolt · Nov 15, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

te CPS is an output device.
its a coil of wire wrapped around an iron core.
pass a metal object(flywheel teeth) past it and it will produce an AC signal.
once running there is a voltage output thats why you cannot measure resistance when its running.
most accurate test is with the circuit loaded with the correct voltmeter.
either a digital voltmeter with a DVA attachment or a peak reading analog such as the stevens CD77.
dont remember the spec offhand but its in the service manual and the tune up spec guide.
thats why I dont use seloc or clymer much.
factory manuals give better information with less skipping about.
why are you testing the CPS and do you know what it does on that engine .

FrenchFry · Nov 15, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

I am testing the CPS because I get 0 RPM on the tach while the engine is running, I checked electrical connections to the tach, it looks OK.

I did not use the motor since +/-4 years when troubles started in fact, but I started it at least once a year, to summarize the engine only started when yellow cable to bypass the computer was disconnected, then starting it like this , stopping it and reconnecting the cable, the engine started on "normal" circuit and I had the RPM information.

This year, it appeared impossible to start it on the normal circuit, started only when yellow cable disconnected. I decided to check everything on the engine, to make it work correctly and to correct all the sxxt mecanos here made on it (they removed thermostat, made me change stator, ignition coils, etc, etc, then said the CDI/computer had to be changed, etc)

I know what the cps does but frankly speaking I don't really get a few things, now the engine starts whether the yellow cable is connected or not, don't know why exactly, don't really see the relation with other things I corrected, but I think the computer is not operating (based on posts on this forum, I checked that correct voltage output was provided to the computer), I suspected thermo-sensor but it works (not in the range of seloc specs, but as you say it's not reliable), so I suspect the cps, and if it is not him then maybe the computer is dead (but would be a bit surprising because I have two CDIs, and same behaviour with the two)

Or maybe I am completely wrong and could be something else, sorry, I don't see logical relations in what I am describing but that's the situation and I am about sure the computer does not operate and/or is bypassed

rodbolt · Nov 16, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

I see your post says your in france.
means you may not have a US market motor but Ill try.
that system uses three pulser coils to trigger 6 ign coil outputs to the CDI.
the computer can modify this.
the ECU simply modifys the ign timing based on various inputs to it the CDI is a stand alone.
however in that year range for the us market we had A and B connectors to achive ECU bypass.
when the ECU is bypassed timing and fuel enrichment is fixed.
best I recall the ECU sent the tach signal on that engine.
post a model number and let me see what I can dig up.
thermostats are a critical part of that engines operation and MUST be there.
post some pics from port,stbd and rear with the hood off.

FrenchFry · Nov 17, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

OK thanks, yes I am in French "c?te d'azur", I was surprised to discover recently that Yamaha mechanics here don't even have a clue of what is the use of cps or thermo-sensor

The engine is 225BETO 2str V6 year 1990, serial nb starting by 6K7, I will provide full serial nb and pictures.

To ne noted : it has a prime start system

I know it's not a US model and BETO are not so liked here but it looks to me quite similar to the equivalent US motor.

I have seen some trends about yellow computer bypass cable stories too, now it looks like something provokes bypass of the computer independently, or the computer is dead, don't know how to check that, but once started the engine is working quite well for me.

FrenchFry · Nov 17, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

I forgot to say : yes I put back new thermostats and everything else that had to be there, changed gaskets at the cylinders, changed prime start with another one I had, same for ECU/CDI, changed water pump, checked idle position, oil pump and other stuff like tps, could not check themo-switches

Knowing that starter, 6 ign coils and stator were changed recently, everything is almost new on this motor

FrenchFry · Nov 18, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

Hi,

First pictures here taken some time ago, we don't see everything so I will take others :

http://www.infonais.fr/Moteur1.jpg

http://www.infonais.fr/Moteur2.jpg

http://www.infonais.fr/Moteur3.jpg

http://www.infonais.fr/Moteur4.jpg

FrenchFry · Nov 23, 2009

rodbolt · Nov 23, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

whew
this is gonna be fun.
judging from the blistered plug caps this motor suffered a terrible overheat in the past.
judging from the chopped up wiring and the hood latches the techs in franch simply dont like the japs.
do you have access to the diagnostic test lamp ?

FrenchFry · Nov 25, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

Looks so bad ?

The "chopped up wiring" it must be me for the tests, Il will arrange that later

What's wrong with the "hood latches" (don't understand) ?

"blistered plug caps" --> spark plugs ???

Sorry, not easy to understand specific terms

Then the terrible overheat might have been before I bought it, french mechanics never saw it, it was working fine, nobody never noticed anything

No for the test lamp, same as for the diagnostic codes and the service manual, where can we find that ?

I just remembered another thing, between the time it was working last year with computer and the time it was working this year but with no computer, I just changed the fuel line from the tank to the motor and the thing we press to push fuel (don't know the name in english)

rodbolt · Nov 25, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

trust me, your engine has been cobbled.
looks baaaad.
I see the same cobbling in Venezuela.
untrained techs working with no service support or manuals attempting to make it go, some more.
look for someone that can sell you a copy of LIT-18559-00-01.
Ill try to help but its gonna be hard.
lets start back with what its supposed to do and what is it not doing.

FrenchFry · Nov 26, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

I trust you, just wondering why what you see with pictures only they don't see it here in real (but don't forget the mess with electrical cables, it's me)

Woow... what I thought after all I have done was probably a simple thing to fix (computer bypass because of wrong sensor or other) looks to turn into something more complicated

I will get the manual if I can (looks like it can be bought on iboats), sorry to ask but it does refer to 1994-2004 years, mine is 1990

Don't want to bother too much if the situation looks desesperate, so I will keep in touch again once I have the manual or do you need something more now ?

rodbolt · Nov 26, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

let me double check that manual number can be one of 2 and I dont have them here at the house.

rodbolt · Nov 27, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

here is an even better spec guide number,covers 84 to 2005 up to 250 HP.
LIT-18559-84-05

FrenchFry · Nov 29, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

Thanks, I ordered it and will follow up (mut maybe not before end of winter here in March)

FrenchFry · Dec 11, 2009

Re: Yamaha 225hp 2str Crank Position Sensor test

Rodbolt, I got the book, now I am not sure which page does refer to my motor. If I look to 225 HP pages for 1990 it does not say a lot about computer codes or thermosensor for example.

Looking at other pages it seems my thermosensor is faulty, it shows at 20?c +/- 3Kohms which is according to the manual the resistance for 100?c

What do you think ? Could be the cause of the troubles ? If not what do you suggest to check first ?

FrenchFry · Jan 24, 2010

Re: Yamaha 225hp 2str Crank Position Sensor test

I bought a new thermo sensor and the resistance is the same as the old one and does not correspond to the values specified in the book, I don't understand, what am I supposed to do now with the manual ?

rodbolt · Jan 24, 2010

Re: Yamaha 225hp 2str Crank Position Sensor test

I warned you that not all international market motors were identical to US market stuff.
to test a thermosensor freeze it,hook up your ohm meter and set it in hot water.
what your looking for is the resistance change.
should be very high when cold and much lower when hot.
my tune up guide doesnt list the resistance specs for a thermosensor on a 1990 225.
but even if it fails it will either cause hard cold starting or a rich running condition depending on the failure.

Yamaha 225hp 2str Crank Position Sensor test

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