Yamaha F225TXR issue

[Flyfishsail]

I’ve been reading a ton of the posts in this site and it’s quite impressive the amount of knowledge shared.

I'm looking for any idea in an issue I have with a newly acquired motor. It’s a F225TXR with 95 hrs total that has sat for a long time with the normal ethanol issues. I’ve replaced the fuel lines going to the engine, added a 2 micron filter in addition to the 10 micron Yamaha spin on. Replaced the VST screen (didn’t clean the needle valve, oops) replaced the F filter above the VST, and the onboard fuel filter. I have also had the injectors tested and cleaned and replaced the spark plugs.

My issue now is the engine runs excellent until about 2000 RPMs. If I go much above that, it’s bogs down and reducing the throttle makes it run well again and gain a few RPMs. I’m now looking into if fuel pressure relief valve is malfunctioning. The engine starts well, high pressure pump kicks on with the key for 5 seconds, and while running the bulb doesn’t get soft. Also pumping the bulb doesn’t have any effect when it bogs.

Any idea on where I should look next would be appreciated!!

Thanks!

[fairdeal]

I I'm now looking into if fuel pressure relief valve is malfunctioning.... Also pumping the bulb doesn't have any effect when it bogs.

If your problem is fuel starvation due to the VST running empty -
the primer bulb should be a helpful diagnostic.


You should be able to easily use the bulb to fill the VST completely -
so that the float/needle valve closes,
and the bulb 'gets hard'.

Now if you do that -
if you confirm, from the behavior of the bulb,
that the VST is being kept full -
and the engine still bogs,
then the problem is NOT the VST running empty.

But if you are unable to fill the VST -
unable to 'get the bulb hard' -
then you need to figure out why;

it won't be the fuel pressure relief valve,
because even if that valve were malfunctioning,
the bulb would still be able to fill the VST.

[Flyfishsail]

That’s a great explanation. Thank you. I am able to pump the bulb with out the engine running and it goes hard. When running at 2000 rpms the bulb won’t go hard. Maybe I should change the engine fuel water separator again?

[99yam40]

Since you said " Also pumping the bulb doesn’t have any effect when it bogs" and if the rail pressure drops, you must be sucking air instead of fuel with the lift pump and the bulb.
you need to monitor rail pressure and VST pressure
lift pump should run all the time at 2000 RPM.
all connections on the suction side of the pump would be suspect, but since the bulb does not help then I would guess it would have to be between the bulb and tank
as said need to monitor pressures to see what is going on

[Flyfishsail]

Great! I’ll put on the fuel pressure tester and run it. Thanks so much for the guidance 99yam40 and fairdeal!

[Keithbaja]

Fuel pressure and then volume are 2 completely different issues !!

[Crazydays]

Did you figure out the problem flyfishsail.
I have similar problems and have researched the net without a solid answer.

[boscoe99]

Did you figure out the problem flyfishsail.
I have similar problems and have researched the net without a solid answer.

Trouble shooting by reading the internet can be a big waste of time. Sends folks down the rabbit hole. They wind up with lots of perfectly good used spare parts.

Start a new post. Describe your model. Describe what you are seeing, hearing, smelling, touching, tasting, etc.