Yamaha EFI Question

[TomS]

Ok, I've been slowly learning about how my 0x66 works by reading through the archives here, service manual, etc. Thanks Rodbolt!<br /><br />Let me see if I understand how some of the EFI components work.. For example, I was trying to figure out how a bad/failed O2 density sensor could lead to an over-oiling condition.<br /><br />1 - Assume 02 sensor fails, and voltage goes high, say .9V<br /><br />2 - CDI thinks the engine is running "fuel rich"<br /><br />3 - CDI changes the fuel injector map to decrease the amount of fuel being injected<br /><br />4 - Because oil injection is controlled by a mechanical link to the throttle body, the amount of oil injected into the system cannot be adjusted by the CDI, correct? So if there is the same amount of oil being injected for a given throttle position, there will now be relatively less fuel in the mix. So the engine becomes "oil rich"<br /><br />5 - The excess oil leads to carbon build-up, excess smoking, and blue smoke. At high RPMs, the engine gets starved for fuel (because the CDI believes there is too much fuel from the faulty O2 sensor reading) and stutters or limits WOT RPM.<br /><br />Does the above make sense?<br /><br />At some point I assume that the CDI determines that the signal coming from the 02 sensor is so out of whack that it goes into a "fail safe" mode, which I believe defaults to a "fuel rich" condition. This means that there is relatively more fuel for the same amount of oil.<br /><br />What is the result of a "fuel rich" condition on the engine? I assume the engine can't burn all the fuel, so you might see some excess fuel coming from the exhaust, or maybe some black smoke?<br /><br />Thanks,<br /><br />-- Tom

 

[rodbolt]

Re: Yamaha EFI Question

mostly correct, except for the failsafe. the CDI does not recognize a signal that is in range but incorrect.<br /> thus it leans out the air/fuel mix until a piston pops.<br /> an over rich condition wil be an indication of a failed ign component,blown low pressure pump diaphram,bad rail pressure regulator,failed VST needle or a leaking injector.<br /> the oil mixture is mixed in the VST so it really does not vary much.<br /> you will most likly pop a piston long before it goes oil rich.<br /> thats why all the service stuff says do not run above 4000 RPM if you suspect a faulty O2 sensor.<br /> the O2 sensor adds a corrective voltage to the ECU to fine tune the fuel delivery in conjunction with TPS and the CPS and a few other sensors.

 

[bernieb]

Re: Yamaha EFI Question

tsheehy,there is also a great answer for you on (thehulltruth.com) scroll down to bottom hit yamaha then on to yamaha 250 smoking ,"grin" has a lengthy reply on your concern.

 

[TomS]

Re: Yamaha EFI Question

Thanks Bernie, I am in fact, stripertom <br /><br />-- Tom

 

[rodbolt]

Re: Yamaha EFI Question

wow. what a site the hulltruth is running, never saw so much incorrect info on an ox66 yam in my life.<br /> however some of it was correct.<br /> the biggest fallacy in the world is the ECU failsafe. even with the sensor dissconected it has no failsafe but will set a computer code, but only if its dissconected.<br />if its failed or defective the ECU will react to whatever the signal is. if its less than .3V it will be rich if its more than .7v or so it starts leaning the mix.<br /> if its lean and you attempt a run for any length of time above 4000 RPM you will find out the cost of pistons and labor rates in your area.<br />thats why its included in the failure section of the tech guide,school books. however it has a note that it should not be run above 4000 RPM and top speed CANNOT be reached.<br />as the ECU is looking for a constantly varying voltage you would think they would have added a failsafe but they did not. the engineers were relying on the consumer would actually maintain such an expensive motor.

 

[TomS]

Re: Yamaha EFI Question

Thanks very much for the feedback Rodbolt!<br /><br />As you have seen, without having real training and the info direct from Yamaha, we are stuck fending for ourselves and asking a lot of questions. Sometimes the people who answer the questions mean well, but don't know the answers.<br /><br />That is why this place is different <br /><br />In any case, I feel like I have dodged a bullet after testing my O2 sensor last fall to see the output voltage slowly increasing up to around .9V where it would hover. <br /><br />Luckily for me, I stay right around 4k RPM when cruising around. After several un-successfull attempts at clean up, I replaced it with a new one.. as well as handling most of the required maintenance as outlined in the service guides and the informative posts here in the archives.<br /><br />Thanks again, you may have saved me blowing an engine I can't afford to replace.<br /><br />-- Tom

 

[HeadHunt]

Re: Yamaha EFI Question

rodbolt,<br /> Please evaluate this comment from THT regarding an O2 sensor and failsafe:<br /><br />"HeadHunt - you could not be more wrong. If no output from a failed O2 sensor is seen by the ECM, the system will stay in open loop condition, which is the same as when you first start your car, until the O2 sensor is heated up enough to start sending the voltage fluctuation based on O2 content to the ECM. Once the O2 sensor is heated up enough to send a voltage fluctuation to the ECM based on O2 content in the exhaust gases it then goes into closed loop mode. This is where all sensor input is used to calculate the fuel and spark curve to meet the condition. So It's not a fail safe mode but in open loop condition the engine is running at some predetermined fuel and advance curve as setup by the intial program in the ECM. This by the way is a rich conditon as opposed to a lean condition. An O2 sensor when it goes bad sends no recognizable voltage swing output, something other than .1V to .9V swing. A failed sensor will either send no output or a constant .45v to the ECM, this is considered the midpoint which is neither rich or lean, and no oputput will keep the ECM in open loop mode. A constant midpoint voltage of .45 is recognized by the ECM as an incorrect value, so it stays or reverts to open loop mode.<br /><br />So to answer the quesion correctly a bad O2 sensor on the OX66 Yamaha outboard will keep the engine in open loop mode which btw is a rich conditon, and it will not burn a piston. Anyone that says it will does not understand the theory of the O2 sensor. This BTW is why when an 02 sensor goes bad usualy carbon fouled in an OX66 engine, you will see more smoke, and the engine is not burning at optimal air/fuel ratio of 14.64:1, but something higher. Therefore you will loose rpms!<br /><br />don't know where you are getting your facts from, but no one is talking about failsafe but open loop vs closed loop. The ECU in order to change the mapping needs a voltage swing! Not a constant voltage, a constant voltage is considered incorrect! When an O2 sensor goes bad it either reverts to constant or no output at all, the ECU will not recognize a constant as a legit input and revert to open loop. I know this for a fact because I was on the development team that designed the Chrysler technician diagnostic terminal which was formulated based on sensor technology. It's the same for all engines since OBDII is a common system. Yamaha uses the same methodology! <br />BTW - the statement you refer to is a statement based overall on a lean condition, not on the O2 sensor theory! Which was very evident on engines that are carbed. If a carbed engine has fuel delivery problems either from a blocked jet or bad fuel pump, you will get a lean condition! The same goes for an injector failure on the Ox66! <br />I agree with only part of your explanation that going to the higher value is to signal more lean. But the ECU has to see voltage swing in order to stay in closed loop mode! <br />Believe what you want but your information is not entirely correct. So if your facts are correct please help me understand why when an O2 sensor goes bad you see more smoke and less rpms! Reason being it's running rich!"<br /><br />rodbolt, this discussion got going about O2 sensors going bad and would they potentially blow pistons. One guy offered the above explanation. Sound accurate??<br /><br />HH

 

[hiflyer]

Re: Yamaha EFI Question

headhunter could you contact me on triumph. I have a major lemon 04 191 158 days in repair status owned 230 days would like some imfo e mail me at rockman12@earthlink.net thanks

 

[hiflyer]

Re: Yamaha EFI Question

headhunter could you contact me on triumph. I have a major lemon 04 191 158 days in repair status owned 230 days would like some imfo e mail me at rockman12@earthlink.net thanks

 

[rodbolt]

Re: Yamaha EFI Question

head hunt, does not work like that for yamaha's ECU map. works like that on all the automobiles I have seen but not OX66 ECU.<br /> dont care what youre auto manual says.<br />let me type a passage from the fail safe function manual page 6-16 of the electrical system traing course,OX66. <br /> code is -- meaning its going to be a non readable code generated by the ECU, symptoms,no signal from O2 sensor,<br />fuel system effects,fuel injection fixed,rich at low speed and lean above 4000 RPM. do not exceed 4000 RPM,<br />ignition effect. none.<br /> engine,reduced engine idling speed and top speed CANNOT be reached.<br /> the yamaha ECU is not loking for a failed O2 sensor, if its steady at .3 or steady at .9 it reacts to the signal. if its unplugged it will detect it and fix fuel pulse/delivery at low speed rich,high speed lean and DO NOT run above 4000 or your will price pistons.<br /> you can watch the pulse width with a decent DVM set to pulse width. and as the 2.6L engine does not have a knock sensor the leanout is excacerbated by detonation.<br />so no headhunt ya really should send a letter to Yamaha, we verified most of the failsafe table in the tank and on the water.<br /> a bad O2 sensor will set no codes nor alarms and the motor can and will go poof.<br /> its the auto guys that keep me in da bidness <br /><br /> but no the ECU mapping on the 2.6 and 3.1 motors does not care about any swinging to go to open or closed loop. all its looking for is a signal detect. open loop on these engines defaults to a fixed injection, rich at idle and lean above 4000.

 

[rodbolt]

Re: Yamaha EFI Question

head hunt, does not work like that for yamaha's ECU map. works like that on all the automobiles I have seen but not OX66 ECU.<br /> dont care what youre auto manual says.<br />let me type a passage from the fail safe function manual page 6-16 of the electrical system traing course,OX66. <br /> code is -- meaning its going to be a non readable code generated by the ECU, symptoms,no signal from O2 sensor,<br />fuel system effects,fuel injection fixed,rich at low speed and lean above 4000 RPM. do not exceed 4000 RPM,<br />ignition effect. none.<br /> engine,reduced engine idling speed and top speed CANNOT be reached.<br /> the yamaha ECU is not loking for a failed O2 sensor, if its steady at .3 or steady at .9 it reacts to the signal. if its unplugged it will detect it and fix fuel pulse/delivery at low speed rich,high speed lean and DO NOT run above 4000 or your will price pistons.<br /> you can watch the pulse width with a decent DVM set to pulse width. and as the 2.6L engine does not have a knock sensor the leanout is excacerbated by detonation.<br />so no headhunt ya really should send a letter to Yamaha, we verified most of the failsafe table in the tank and on the water.<br /> a bad O2 sensor will set no codes nor alarms and the motor can and will go poof.<br /> its the auto guys that keep me in da bidness <br /><br /> but no the ECU mapping on the 2.6 and 3.1 motors does not care about any swinging to go to open or closed loop. all its looking for is a signal detect. open loop on these engines defaults to a fixed injection, rich at idle and lean above 4000.