Fuel starvation yamaha f225 i need help

[marchmadness]

I AM AT THE END OF MY ROPE. MY ISSUE IS WITH FUEL STARVATION ON MY 03 F225. THE MOTOR RUNS ANDS STARTS PERFECT. I RUN THE MOTOR FOR A WHILE AND I SHUT IT DOWN TO FISH. STARTS UP FINE ( NO HOT START) I THROTTLE UP AND IT DIES. THIS ALL STARTED LAST YEAR AROUND THIS TIME. SO I ENDED UP REPLACING THE PRESSURE RELIEF VALVE. AND NOW THIS YEAR SAME ISSUE . I SQUEEZE THE PRIMER BALL TO REFILL THE VST STARTS UP AND OFF I GO . SO DECIDED TO REPLACE THE LIFT PUMP. TODAY WAS MY SECOND TIME OUT AND IT DIED AGAIN. I DONT KNOW WHERE TO LOOK.

[pstephens46]

Intermittent power issue to pump?

[fairdeal]

deja vu....

yes, intermittant pump operation is at least a theoretical cause

a flow restriction - on either side -

or air leak on the suction side are possibilities


- patch in some clear tubing on the suction side of the pump and look for air bubbles (as 99yam always advises)

- use a fuel pump tester gauge to measure vacuum on the suction side - there should be none measureable -

- test pressure on the outlet side - should build to ~14 psi once the VST is full

[99yam40]

OP turn of the caps lock please.

is the pressure suppose to be that high (14) out of the lift pump?
I though the pressure relief was around 10

[marchmadness]

sorry for the caps

[fairdeal]

sorry for the caps

you're understandably stressed.

it'll be OK - you'll get this figured out.

[fairdeal]

is the pressure suppose to be that high (14) out of the lift pump?
I though the pressure relief was around 10

AFAIK Yamaha has not published a spec -
the only testing protocol I've seen simply confirms it functions as a "check valve" -
without referencing pressures.

IIRC Rodbolt is the source of the 10 psi value.

My testing also shows it begins to opens around there -

the upper limit for it - or any pressure con*****er - is affected by the volume it is attempting to control.

FWIW on my F225 it was approaching 15 psi :

https://vid.me/BZlf

[99yam40]

I thought I remembered you test showing it started opening about 10, just did not remember the pressure going up that high on a working system

[marchmadness]

I am back on duty for the next couple days and I'll get back to it Wednesday I just had a couple of questions to check for air bubbles what I put the clear plastic tube in the fuel line before it tees to the pressure release valve or directly to the low fuel pump . If I do have air leak why does it only show up after the shutdown ? Another question is where does the fuel go if the pressure release valve does open ? This is a close system the fuel should just flow back into the VST correct ? Or is the fuel somehow backing into the gas tank ? There is also an air vent and check valve that goes from the VST tank to the airbox to vent their fuel vapors could that be clogged.

[fairdeal]

you want the clear tubing at the infeed of the lift pump

there are actually re-circulating loops

before the VST -
when the VST needle valve closes, but the lift pump runs -
fuel flows back to the lift pump inlet through that "check valve"

essentially the lift pump "chases its tail" - pumps "in a circle"

the pressure regulator on the fuel rail also forms a loop -
fuel pumped into the fuel rail by high pressure pump but not injected
escapes via the presure regulator, flows through the fuel cooler,
and then back into the VST -
there's a brass fitting about 1/2 way down on the front

[99yam40]

If that motor has a fuel cooler, make sure it is getting proper water flow thru it.
could be boiling the liquid fuel out.

but that would still mean that the pick up pump is not pumping as it should refilling the VST

[fairdeal]

the theory behind why your fuel "starvation" shows up when it does -

below 1200 rpms the lift pump only runs "part time" -
10 seconds on, then off for 20 seconds.
Above 1200 rpms it runs continuously

if your system is not working optimally - because of a restriction or air leak -

then it may be barely keeping fuel in the VST while running under 1200 rpms

and just barely keeping enough going in when on constantly over 1200 rpms

so when you shut off - it may be with a nearly empty VST.

And a hot engine could then "boil off" (vent) the remaining fuel

[fairdeal]

a good spot to check for any air leak

[99yam40]

the theory behind why your fuel "starvation" shows up when it does -

above( below) 1200 rpms the lift pump only runs "part time" -
10 seconds on, then off for 20 seconds.
Above 1200 rpms it runs continuously

if your system is not working optimally - because of a restriction or air leak -

then it may be barely keeping fuel in the VST while running under 1200 rpms

and just barely keeping enough going in when on constantly over 1200 rpms

so when you shut off - it may be with a nearly empty VST.

And a hot engine could then "boil off" (vent) the remaining fuel

Fixed it for you

[fairdeal]

Fixed it for you

thanks!
good catch - I went back and fixed it