OX66 250 not firing injectors

[Kingfish999]

ok then lets look at what he said maybe this will be easier to read than a paragraph:

my advice???
learn how the system works and QUIT splatter gunning.
at key on the injectors receive 12V via the main relay. the ECU controls the ground path. that path is only there for about 2.5ms per revolution at idle.myself I would test rail pressure and look at the injector filters.
if you lose a pulser signal you also lose spark and fuel on two cylinders. the six pulser coils control spark and fuel for six cylinders.

how am i suppose to learn how the system works when i dont have info on how it works? service manual gives 0 info. but i know enough about automotive EFI to know the basics of the system

i am aware the injectors are con*****ed by the ECM grounding them. that's how i force the injectors to fire. using a paperclip to back probe the connector between the ECM and injector and force the injector to fire by grounding it out. i can force a couple injectors to give a couple squirts and the engine will run for a short time till it uses up that fuel. yes it is getting 12v at the rail

i have tested fuel pressure. countless times. found a bad fuel pump due to fuel pressure slowly dropping at WOT and then later a bad fuel pressure regulator because the pressure would stay super high almost 100psi. this was months before this issue. fuel pressure is perfect ever since.

i am getting spark at all 6 plugs and consistently. but i am getting no fuel injector pulses at all.

I am gonna try this one more time.
you already know the ECU fails to see at least one pulser coil signal.
code 13.
the ECU uses all six pulsers to trigger spark AND fuel.
#1 pulser gives the ECU the trigger signal to spark #1 and trigger injector #2.
#2 injector sparks #2 and triggers injector #3 and so on and so on.
loss of fuel pressure can trigger a code 13, so can a wire issue or loss of the pusler ground.
see how easy this is?
no splatter gunning just basic knowledge and a method.
myself I would carefully test pulser outputs, make sure the outputs make the ECU then test the voltage across the injector.
the injectors use 12v the ECU supplies the ground in the millisecond range. most digital meters wont see it.
use an analog meter..
by measuring the injector resistance and a bit o math using Ohm's law you can get an idea of what to expect the injector voltage drop will be.
the s and sx 3.1 motors are a tad different then a Vx.
the VX does NOT use CCS.

i understand the engine uses the pulse coil to control spark and fuel. but when i am getting all 6 plugs firing and no injectors firing

dont see how low fuel pressure can cause a code 13. how do you figure that? the ground of the pulser coils is good. so do the other 3 known good ones i tires

im not throwing parts at it. i am diagnosing it. but when the service manual gives me a test and it passes all the tests, swapping known good parts becomes the next step.

i have used an LED test light to view the pulser signals for each of the 6 wires. they were consistent. i have used a peak voltage adapter on a digital meter to verify the voltage is to spec. it is. today i used a analog voltage gauge to verify the signal it is still good and consistent.

[99yam40]

well if pulling the plugs helps the motor turn over faster and the injectors fire then but not when you put the plugs back in, it could be that the voltage to the injectors is being pulled down to far when turning motor under a load(compression)

Did you measure pulser voltages when you pulled the plugs to see if that changed the pulser outputs?
usually the specs given are minimum. maybe turning faster could be higher voltage out of them.
But then if the ecu was not seeing them it would not be sparking the plugs also
just something to try

[rodbolt17]

a unique issue with the 3.1l oil switch assy.
the clover leaf looking piece of rubber that centers the assy in the filter has a tendancy to curl upwards.
this prevents the float from its down position and can allow the oil tank to run dry with no alarm.
that is why Yamaha recommended to check the water trap and transfer once a month. no one ever does but it is in writing.

this issue should have been solved in about 1 hour.

however if fail to use the proper tools and have no understanding of what you should see you end up with a lot of splatter gunning.
and still a dead motor.

[boscoe99]

however if fail to use the proper tools and have no understanding of what you should see you end up with a lot of splatter gunning.
and still a dead motor.

Guy on another site has a four stroke Yam that is going into RPM reduction mode, sounding the alarm and turning on the over temperature icon. He said he changed the oil pressure switch and it did not solve the problem.

I asked if the low oil pressure icon illuminated would he change the temperature sensor. He was not pleased.

[DennisG01]

a unique issue with the 3.1l oil switch assy.
the clover leaf looking piece of rubber that centers the assy in the filter has a tendancy to curl upwards.
this prevents the float from its down position and can allow the oil tank to run dry with no alarm.
that is why Yamaha recommended to check the water trap and transfer once a month. no one ever does but it is in writing.

I've been following this thread to learn more about my engine. I looked through my service manual (the area that talks about the oil system and also the maintenance section), but there is no mention of checking the water trap - is there another publication that has more "maintenance" suggestions/items? FYI, I do look at the water trap (assuming that it's that vinyl tube hanging off the bottom of the engine oil tank? Probably a good idea, though, that I disassemble the tank and clean it out. I know that drive lube can get gunky inside the remote drive lube bottle on Mercruiser engines... not sure about 2-stroke oil, though.

This "clover leaf" thing... I don't see anything in the parts breakdown, but would I be correct in assuming that if I take apart #1 and #2 (Oil level sensor and Oil level strainer) that I would find it? (click image or drag to a new folder to make it bigger)

[Kingfish999]

spent abit of time on it today. was taking vidoes of every test and results i have. got dark before i canfinish making clips

but by chance when we unplug the thermosensor on the top of the block the engine starts up perfectly. we plugged it back in and it would keep starting up fine after because fuel was now in the intake. so we unplugged the injectors and cranked it to clear all the fuel from the intake and tried and tried again it would not start. but soon as we unplugged it again it would fire right up. so it acts like sensor is the cause but the ohm test shows it as very close to spec from room temp to boiling and the sensor did not show any continuity between the body and the connectors.

while i would like to replace the sensor and call it good but i have a fealing it is not the actual issue.

i guess im blind. i dont see what your wanting me to test. as far as im concerned i have done your tests

[DennisG01]

King, by the way, sorry about the slight hijack there. It was a question I was wondering about and posted it just in case you may have had the same one.

[boscoe99]

I've been following this thread to learn more about my engine. I looked through my service manual (the area that talks about the oil system and also the maintenance section), but there is no mention of checking the water trap - is there another publication that has more "maintenance" suggestions/items? FYI, I do look at the water trap (assuming that it's that vinyl tube hanging off the bottom of the engine oil tank? Probably a good idea, though, that I disassemble the tank and clean it out. I know that drive lube can get gunky inside the remote drive lube bottle on Mercruiser engines... not sure about 2-stroke oil, though.

This "clover leaf" thing... I don't see anything in the parts breakdown, but would I be correct in assuming that if I take apart #1 and #2 (Oil level sensor and Oil level strainer) that I would find it? (click image or drag to a new folder to make it bigger)

Yamaha data is very poor with respect to informing customers as to maintenance related matters.What rodnut is referring to is technical information that gets issued to dealers only. The customer gets an owner's manual only. The customer can buy a service manual if he wants but they are really lacking in quality information.

Notice that rodnut makes reference to 3.1 liter motors only. Others may not have the same issue.

This is from a Marine Technical Guide. Issued to dealers only.



This is from an owner's manual.

[boscoe99]

And please notice that Yamaha calls the assembly that includes three switches as a "sensor". The switches are sensing the oil level in the tank.

[DennisG01]

Thank you, Mr. B! Where there different displacement 250HP OX66's over the years? Mine is a 2000 model.

[boscoe99]

Thank you, Mr. B! Where there different displacement 250HP OX66's over the years? Mine is a 2000 model.

I suspect that all 250 HP OX66 models were 3.1 liter displacement. Don't know for sure.

[DennisG01]

I suspect that all 250 HP OX66 models were 3.1 liter displacement. Don't know for sure.

OK - thanks. I had thought that was the case, as well. I'll do some more research, though.

[Chitownred0512]

Kingfish999 was your problem ever solve? If so how