Headaches w/2000 250 OX66, Please Help!!!

[21Contender250]

I have a 2000 Yamaha 250 OX66 which has a rebuilt powerhead. The last few weeks I have been in the process of getting the motor rigged. Along the road, there have been a lot of bumps. Long story short, I had an oil pump problem which turned out to be a bad CDI Unit which we replaced last week. This past Saturday, dropped the boat in the water and it started right up. I noticed that it was running a bit rough, but, just figured it was from the double oil. Put the motor into gear and then I really could notice a problem. The motor is running as if it is in guardian mode and only hitting on 2 or 3 cylinders. I upped the RPM's a bit and the motor had nothing to give. It made the boat shake in the worse way possible. I immediately took the boat out of the water and back up to the garage. There were no alarms what so ever. My understanding is that the motor could be stuck in guardian mode. However, after I took the boat out of the water and went to run it on the hose, the motor only cranks over while not firing. I am at a loss for words right now. I became frustrated and called it quits at that point. Do you guys have any thoughts? Can't get the motor started to try and check sensors to see if that could be the problem. Please let me know what I need to check. Thanks in advance.

 

[99yam40]

Re: Headaches w/2000 250 OX66, Please Help!!!

You need a peak reading voltmeter or a DVA adapter and DMM and a manual to check the inputs and outputs of the electronics to help locate where the problem is.This can be done while just turning over.
If all the inputs to the CDI are in spec and no output then it could be kill switch, key switch,wiring, or the CDI.

Are you sure it is not a fuel problem?

 

[rodbolt]

Re: Headaches w/2000 250 OX66, Please Help!!!

there are NO issues with the CDI that can cause an oil failure.
alarm issues,yes.
the CDI does NOT control the engine oil pump just the transfer pump.
however IF the alarm system works,and its simple to test, you have about 20 minutes of oil in the engine tank when the alarm triggers.
IF the alarm works and the keyswitch kill circuit is grounded it sounds when you crank the engine.
dont need to start the motor to test any sensor on that engine.
all can be tested while static.
you can also use the diagnostic test lamp.
are you doing this or a trained tech?

 

[21Contender250]

Re: Headaches w/2000 250 OX66, Please Help!!!

The low pressure pumps are new. The VST tank has been serviced and the fuel pressure is holding steady at 36 lbs. or so. I will check out some more things tomorrow afternoon following work. As far as the kill switch goes, it has not been disengaged. Question, would changing out the CDI Units have any affect? Thanks for the help so far!!!

 

[rodbolt]

Re: Headaches w/2000 250 OX66, Please Help!!!

what type of spark tester are you using to determine a no spark on all 6 cyl condition?

 

[21Contender250]

Re: Headaches w/2000 250 OX66, Please Help!!!

I first checked that the fuel pump was functioning when the ignition key turned on. Second, I checked each spark plug whiling finding 4 out of 6 plugs with very loose end caps. I went ahead and tightened down the four loose ends. Third, I turned over the motor and she fired right up. I then went out and dropped the boat in the water at the ramp as I could not find the muffs to fire her up again on the hose. So, I dropped the boat in the water while keeping her on the trailer and it would not fire. Turned it over and over, but, still no fire. Went ahead and took the cover off and confirmed again that the fuel pump was coming on when the ignition key was on. After a bunch of cranks, bang, she fired right up. It sounded rough again and about to stall so I adjusted the idle a bit higher. After it ran for a while at a higher idle and got warmed up, I put the cover back on. As soon as I put the cover on, she stalled. Took cover back off and she fired. Put cover back on while running and she stalled again. So, next time she was running with cover off, I fooled around with some wires. Here is where I found a 4 wire wiring harness at the top of CDI Unit and brown was only partially attached. Plugged back in and she was back to normal. Well, not normal, but, starting right up and running. Let her continue to run and then tried to rev it up there at the ramp. Still, not hitting on all cylinders. Tried putting it in gear and pushing the throttle forward and it had nothing to give and sounded like crap while producing the rough vibration throughout. As soon as you come off the throttle, the motor just about dies and sounds at its worse like it has a horrible virus. Anyway, the motor starts up as I have figured out the starting problem. But, we are back to the running very poorly and not hitting on all cylinders. Could it be the CDI Unit, bad motor wiring harness, etc.... I think we are close, but, still need some help. Thanks again.

 

[21Contender250]

Re: Headaches w/2000 250 OX66, Please Help!!!

Fuel is new, fresh and stabilized in addition to the double oil. Original powerhead had an injector problem causing it to lean out. That has all been fixed including the main internal components replaced. I plan on checking the O2 sensor, changing out the plugs and checking the throttle position sensor. My understanding is that the throttle/gear position sensor could be bad while not allowing the final 2 cylinders to kick in.

 

[rodbolt]

Re: Headaches w/2000 250 OX66, Please Help!!!

dude
where are you getting your information.
its obviously FLAWED.
do a forum search on home made spark checker.
your gonna need it.
do a search on a DVA meter or a DVM with a DVA adapter. RMS voltage is NOT peak voltage regaurdless of what you may read on the net.
do you have a clue on the proper procedure to check or adjust the TPS,which has NOTHING to do with the CCS system your engine uses.
make sure you understand how and why that TPS needs to be correctly set.
there is NO IDLE speed adjustments on that engine.
it works as designed or its broke. dont tweak screws.
to set the TPS you MUST have the service manual and a digital voltmeter and the harness adapter or be careful and back probe the CONNECTOR, NOT THE WIRE INSULATION with paper clips or pieces of solder.
when cranking and below about 500 RPM the ign sparks all 6 cylinders,between about 600 RPM and about 800 RPM it drops one,between about 850 and 2000 it drops two cylinders.
the only thing the shift cut switch does is make the engine misfire when the switch is closed or a wire is pinched and shorted. this aids in moving from any in gear position to nuetral.
what service manual are you using? if anything but the correct yamaha one your gonna stay confused.
you cannot test O2 sensor output on the muffs.
right now the best 70 dollars you can spend will be on the diagnostic test lamp.
just because the fuel pump whines for 3 seconds at key on power DOES NOT MEAN the high pressure fuel rail is at the correct pressure just means the pump armeture is rotating.
I dont mind helping,I probably know more about this system than the instructors at Kennesaw GA, they hate it when I do the electrical course and I have done it 3 times so far. that and I have been working on them since the mid 90?s when that system was introduced.
but you MUST have the correct manual and some test equipment and at least a theoretical understanding of speed density EFI systems.
if your not careful you can and most likly will smoke another piston.
if whoever is helping you does not have fuel and electrical certs on the wall find another helper,if your doing do some forum searchs on 3.1L OX66 and google speed density EFI theory.
have you actually TESTED the oil and overheat alarm systems?
this should have been done at the first oil transfer.
you may also wish to forum search some precision blend sites as well.

 

[21Contender250]

Re: Headaches w/2000 250 OX66, Please Help!!!

Thanks for getting back to me. I am dropping the boat off tomorrow. I need a set of mechanical eyes to take a look. I have been trying to do it myself, but, I must not be cutting. I will keep you guys posted as to what we find.

 

[rodbolt]

Re: Headaches w/2000 250 OX66, Please Help!!!

good luck.
but keep in touch, we can tell you how to test it but sometimes the test equipment exceeds the cost for a one time deal.
but testing the alarm system is quick,simple and on a 3.1L motor MANDATORY.
there is a quirk with the oil level alarm in the engine tank that MUST be periodically tested.

 

[99yam40]

you should not be posting this on a years old thread
start a new one with all the motor and other info

by the way there is no return to port mode.
there is a reduction of RPM for overheat or low on oil that allows you to get out of an emergency situation ( like getting run over by a big boat or barge) so you can turn off the motor to address the problem