08 250 Yamaha HPDI fouling plugs

[pritch]

Looking for advice regarding fouling of plugs on my 08 250 HPDI. Last week motor ran well for about 5 minutes at WOT but then went into guardian mode plugs that were about 30 hours old were fouled. Mechanic replaces plugs and tried again with same result. He says that two plugs were wet (oily) and says that the caps weren't fitting right so to replace the caps and wires. $56.00 each! I am using Yamalube 2M. Any suggestions?? Does anyone recommend oil change to Merc or Pennzoil Premium plus. Not sure if the Pennzoil is available in Canada.
Thanks for any info.

[JP Love]

Pennzoil only at Bass Pro Shop Vaughan near Toronto and last time in special at $13,95 US gallon. Was synthetic blend.. Verry good oil..

[pritch]

Thanks. That Bass Pro Shop is only 45 min away.

[Superbender]

It is VERY important how you gap these plugs,and do you have the latest oil pump there are numbers stamped on the arm of the oil pump

[F14]

Get a black motor.

[rob@sportsmancenter]

Dont go to yellow death in a bottle(penzoil) got 3 powerheads down because of that crap. What codes are being thrown? Check hp fuel pump and reeds. And make sure plugs are ngk bkr6eku also the oil pump linkrod.

[pritch]

Thanks. No codes. Correct plugs. Not sure about pump. Do you recommend that I stick with yamalube?

[lance]

Some say use Yamalube only, others say not to because how dirty it burns. I’ve chosen not to run it. With Penzoil Premium Plus (semi synthetic), my plugs and prop hub are significantly cleaner than with Yamalube.

I see you have changed some plug wire boots. Make sure each boot measures 4K-6K ohms. They just unscrew from the wires so you can check the resistance end-to-end.

Also, make sure the oil pump rod gap is adjusted properly. The gap is measured with the throttle blades fully closed—not at idle. If you set the rod at idle, the pump will over oil. It would probably be a good idea to check the TPS voltage adustment at the same time as the oil pump rod since the throttle blades will be closed.

Suggest checking over on BBC, Yamaha motors, there is a ton of info there on how to maintain Yamaha HPDIs.

[pritch]

Lance - thanks for your reply. I'll subtly pass these suggestions along to my mech. The wires and boot at $56 each so I'll having him change only the ones where plugs were badly fouled. Thanks again!

[VectorPat]

There are many things that will cause these motors to foul plugs. I doubt its your oil causing it to do it that quickly, but i would stick with yamalube for now. You say the engine went into guardian mode. Fouled plugs will not cause it to do that and if it did go into rpm reduction then there should usually be a code. Did you get a horn? Does your horn work? Is compression ok? Ever had and overheating problems, is so check the exhaust tuner, they have been known to melt or crack. These motor have a couple shift switches as this motor only runs on 4 cyls when in neutral and another switch that will drop the whole stbd bank when shifting out of gear. If there is something wrong with these switches the motor will never run right. Battery voltage will also cause problems, as will fuel pressure. You have 2 lift pumps that have a bad diaphram, an electric pump in the VST and it has a float like a carb, it can flood if thee is an issue with it, and the belt driven high pressure pump that has small filters in it. If there is an issue with any of these pumps it will cause running issues and will foul plugs. There are several filters also. Your mech needs to have his computer hooked to the motor while it is running on the water and not just at the shop on a hose. If there is a loss of fuel press he will need to find out where the loss is as the computer only shows what the high pressure pump is putting out, if it cant get fuel to it then it wont have the right pressure. Your tech also needs to know what he is looking at on the computer as there are things that will cause running problems that will not show codes such as a temp sensor reading too cold which will cause the motor to run too rich or the above mentioned shift interrupt switch that will shut down 3 cyls.

[VectorPat]

I more thing I forgot, make sure the engine is warming up and doesnt have a thermostat stuck open. This will make it run rich also.

[martinc]

Do you mean Suzuki? Thanks Martin

[cali kid]

Hi, Do a LEAK-DOWN.Bet you got slightly scored cylinders.
~ Randy

[johnboy 88 vegas]

We've run into this same problem a few times and switching oil to a synthetic blend will help alot. Keeping a dose of Ring Free or Sea Foam in the fuel will help as well.

[Greg G]

There are many things that will cause these motors to foul plugs. I doubt its your oil causing it to do it that quickly, but i would stick with yamalube for now. You say the engine went into guardian mode. Fouled plugs will not cause it to do that and if it did go into rpm reduction then there should usually be a code. Did you get a horn? Does your horn work? Is compression ok? Ever had and overheating problems, is so check the exhaust tuner, they have been known to melt or crack. These motor have a couple shift switches as this motor only runs on 4 cyls when in neutral and another switch that will drop the whole stbd bank when shifting out of gear. If there is something wrong with these switches the motor will never run right. Battery voltage will also cause problems, as will fuel pressure. You have 2 lift pumps that have a bad diaphram, an electric pump in the VST and it has a float like a carb, it can flood if thee is an issue with it, and the belt driven high pressure pump that has small filters in it. If there is an issue with any of these pumps it will cause running issues and will foul plugs. There are several filters also. Your mech needs to have his computer hooked to the motor while it is running on the water and not just at the shop on a hose. If there is a loss of fuel press he will need to find out where the loss is as the computer only shows what the high pressure pump is putting out, if it cant get fuel to it then it wont have the right pressure. Your tech also needs to know what he is looking at on the computer as there are things that will cause running problems that will not show codes such as a temp sensor reading too cold which will cause the motor to run too rich or the above mentioned shift interrupt switch that will shut down 3 cyls.

Great info here on the HPDI............