200 HPDI power loss at high RPM

[Britfish]

OK, agreed, 2 cylinders are dropped at idle, Yamaha does not recommend over revving in neutral BUT I don't think it should cut out even at a very low RPM.
Any thoughts

[Sequoiha]

HPDI will not accelerate in neutral, at least if all the electronics are working correctly it should not. there is 1 filter that comes to mind, the steel canister medium pressure filter just above the VST, Has this been replaced. for some reason it is missed more than it should,, maybe the price.. it is quite expensive for a fuel filter..

[Britfish]

yes, that filter was replaced, $85 if I seem to remember right.
Yes, they sea tested it and said they got it up to 45RPM. Its going back in there. I didnt realize that there are a few levels of Yamaha registered places, they registered but it looks like they are the lowere tier. Wonder if that makes a differance ???
Could the throttle shift be causing me not to get up to the 50-55RPM range ? I'm thinking its linked to my problems considering the cut out when in neutral (at very low RPMs )
FRUSTRATED !!!!!
Thanks for all comments and help

[99yam40]

from what I have read, Above a certain RPM in neutral the ECU will drop 2 more cylinders besides the 2 that are off at idle to keep the motor from reving.

It is possible that a switch is not telling ECU the motor is in gear, but I do not think it would get any RPMs on just 2 cylinders under load.
And it is easy to see with the computer hooked up

If there is a problem with fuel restriction the rail pressure would indicate that also while hooked up to computer

[Britfish]

Played around with things tonight and learned a lot.
Took an old plug and took turns starting and running briefly while old plug was connected to each plug lead. Its easy to see from here which cylinders are dropped at idle, obviously needed briefly at fire up but to rev in nuetral, only need 4 out 6 to spark.
My issue was a coil connection to another cylinder.
Able to to get up to 51 RPM now, that'll get me to winter, then we start all over again.
Last 3 weeks learned a lot about these HPDI's, great freakin motors but tempramental as hell when it comes to fuel and filters.
My advice - get yourself a really good yamaha guy who wont cut corners on hours spent to maintenance, and if your mechanically wired, all this is pretty basic stuff.
Thanks for the help, looking forward to some winter reading and hopefully helping other folks out.
Thanks yamaoutboard forum, great resource !!!

[rodbolt17]

as you did not give a model number this is generic but applicable.
the Hpdi in 200 HP was made based on both the 2.6L block and the 3.3L block.
the controls are basically the same.
in N it drops two cylinders 2 and 3.
the 2.6L up to 1400 RPM and the 3.3 to about 1700 RPM this is a given.
in in above 1400 or 1700 it drops two MORE cylinders for a total of 4 cylinders shut down.
now we don't fire 2,3,5 and 6 cylinders.
whats amazing is I have actually seen idiots able to rev above 4500 RPM in N .
the shift POSITION switch controls this action. if it fails in the closed position the ECU never sees that the shifter has been moved to an in gear position and it wont go.
if it fails in the open position the ECU sees a start signal and an in gear signal and will default and you wont get much above 2300-2800 RPM.

the first scene the ECU thinks all is normal and will run the partial cylinder operation.

the second scene the ECU got confused cause its not supposed to happen in normal operation and defaulted.

when cranking the ECU sparks all 6 cylinders based on a crank signal input on the brown wire from the start relay.

now, most later dual driver setups also run a shift cut switch, this misfires cylinders to unload the propshaft to allow the shift clutch to disengage the gear.

[mjohnson]

Hope I am in time to save you some $.. Anyways I had the same thing that happened to me with my HPDI and it ended up costing me $2,200.. Ya I was pissed about the whole thing and I could have got away with just extracting 2 basket filters for about $4 total. Google "Hidden Filters " for HPDI engines on the High Pressure pump and you will find out the whole story. The way to tell if its the pump is you have to hook the engine to the computer to check the pressure.. It needs to be 750 psi.. Mine was 50lbs...I sent my High pressure pump into flagship marine and and injectors rebuilt and it was $$ About 80% of the time it is just the basket filter and you can do it yourself and go fishing! If you have bad fuel or debris in tank that caused the plug up then get it fixed cause it will happen again. I changed all my filters b4 I found out about the Hp pump and they were all clean.. I didnt get that they could b clean and the hp pump clogged but I have a 1000hrs on it and they have never been cleaned b4.. F_ck yamaha for not saying anything about these filters they ended up costing me over 2k... I know if it ever happens again I will just change the filters myself and will b done within the 1st beer.

[rodbolt17]

and then the liability for a high pressure fuel leak is yours.
that's why I don't mess with the pumps, I send them to flagship.
I don't have the equipment to test the pump functions after repair.
Yamaha doesn't offer it and flagship made their own.

as I see maybe 1 pump a year lately I simply send them out.

luckily in my area most the HPDI motors are gone.