Yamaha 250 OX66 Poor Accelaration and fouled plugs

[Capt Picon]

Hi Folks,

2000 Yamaha 250 OX66. Idles poorly and smoky, as soon as I hit the throttle it doesn't take off, a lot of shake...like starving for gas. Max RPM that I can reach is around 3000.

One thing that I noticed lately is that the HP pressure pump is constantly running with the key in the initial On position, normally shuts down after a few secs. Installed new plugs not long ago (06/13/2016) they were totally black and oily after only a few hrs.

Motor was de-carbed with sea foam (06/13/2016), spraying thru the intake...lots of smoke.

This is what I checked so far:

Compression: 115 on all 6.
HP Fuel pressure: 36-38 psi. It does goes down to 20 psi when switch the key off.
VST: super clean.
LP Pumps: no leaks...almost brand new.
Fuel line: no restriction.
Fuel/water filter: new Yamaha OEM.
Injectors: filters look clean.
TPS: checked OK.
O2 sensor: cleaned...it was black and oily like the plugs.
Oil Pump link: checked and double checked.
Plug cap: checked resistance 5kohms all 6.

Connected the winky blinky test light: code 33 and then code 1 (tested at home on the ear muff not in the water).

Sorry for the lengthy post. Any ideas ??

Thanks,

Eladio

[cpostis]

Per Rodbolt, Code 33 and then code 1 once reaches normal operating temp is normal. Check out the link to this thread, maybe it will help.http://www.yamahaoutboardparts.com/f...e-th26972.html

[Capt Picon]

Thanks for the suggestion, waiting on Rodbolt to comment.

[99yam40]

I hope that the plugs were replaced after you completed the decarb.
If it was still in progress then that may have caused problems with the plugs

[99yam40]

Thanks for the suggestion, waiting on Rodbolt to comment.

so you will not read the post he sent you a link to that talks about the code 33?

[Capt Picon]

I hope that the plugs were replaced after you completed the decarb.
If it was still in progress then that may have caused problems with the plugs

Yes I replaced with new ones. New ones now look even worst than the old ones.

[Capt Picon]

so you will not read the post he sent you a link to that talks about the code 33?

Yes I read the link...I got code 33 and then code 1.

[Capt Picon]

I Just double checked the TPS and everything seems to be within specs.

One thing that I noticed is when I turn the throttle valve (#1)to the open position, I can't hear the injectors open or closing !!! If my memory doesn't fail me, I remember injector sound whenever I open the #1 valve which is connected to the TPS.

As I mentioned before, the HP pump is constantly running with key in ON position. Seem to me like the injectors are stuck open !!

Any ideas ?

[boscoe99]

I Just double checked the TPS and everything seems to be within specs.

One thing that I noticed is when I turn the throttle valve (#1)to the open position, I can't hear the injectors open or closing !!! If my memory doesn't fail me, I remember injector sound whenever I open the #1 valve which is connected to the TPS.

As I mentioned before, the HP pump is constantly running with key in ON position. Seem to me like the injectors are stuck open !!

Any ideas ?

When the key is turned to the on position the injectors will have 12 volts to them from the main relay. The CDI will ground the pump to make it run for maybe up to five seconds when the key is turned on. If the starter motor is engaged the pump will also run. Once the motor starts the pump will continue to run. Via the CDI grounding the pump of course.

If the HP pump runs with the key on but the motor is not running you have a problem.

The injectors operate the same. Voltage via the main relay and being grounded by the CDI. The CDI grounding all injectors at the same time with the motor not running does not seem correct.

The throttles being opened or closed has no bearing on the injectors being grounded by the CDI.

[Capt Picon]

When the key is turned to the on position the injectors will have 12 volts to them from the main relay. The CDI will ground the pump to make it run for maybe up to five seconds when the key is turned on. If the starter motor is engaged the pump will also run. Once the motor starts the pump will continue to run. Via the CDI grounding the pump of course.

If the HP pump runs with the key on but the motor is not running you have a problem.

The injectors operate the same. Voltage via the main relay and being grounded by the CDI. The CDI grounding all injectors at the same time with the motor not running does not seem correct.

The throttles being opened or closed has no bearing on the injectors being grounded by the CDI.

Thanks for your reply...that's exactly the current situation...HP pump constantly running with key on and motor not running. Maybe my CDI is bad ? All of this maybe causing the erratic idle, smoke, fouling plugs, and not letting the motor hit RPMs above 2500-3000 ??

I'm checking all the wiring connection as we speak, trying to find a problem. Just tested the pump resistor and got 0.7 ohms...should be around 0.5 ohms right ?

[99yam40]

Did you take into count the voltmeter leads resistance when measuring the ohms?

[Capt Picon]

Did you take into count the voltmeter leads resistance when measuring the ohms?

No originally, but I figured that will add some to the final reading (0.1-0.3 ohm)...so my resistor should be ok, right ?

[jf123]

Check the yellow/white connector at the bottom harness of the CDI unit. Disconnect the barrel connector and check for corrosion. It controls the advance timing circuit. It will also make the fuel pump run constantly with the key on engine off.

[99yam40]

No originally, but I figured that will add some to the final reading (0.1-0.3 ohm)...so my resistor should be ok, right ?

Yep, just touch the leads together to see how much resistance they have and subtract that from the reading and compare that to specs

I do not claim to know what the specs are.

just look in your manual

[Capt Picon]

Check the yellow/white connector at the bottom harness of the CDI unit. Disconnect the barrel connector and check for corrosion. It controls the advance timing circuit. It will also make the fuel pump run constantly with the key on engine off.

Thanks for the reply, I will re-check continuity on that connector...for some reason the previous owner replaced the original connector with a crimp butt connector, if I need to emergency start the motor, it needs to be cut !!! Maybe the original connection rusted out !!