F250B dies

[Mackesthlm]

I have a Yamaha F250B year 2009.
It always starts really fine and runs
good for as long as I want.

After I have stopped it and had a break for
about 30 minutes and I start it again it will
run nice on idle but when I start moving it
died after a couple of minutes.

First run of the day never a problem but always when starting
a second time.

Any ideas on where to start the search ?

[rodbolt17]

test the low pressure fuel system.
try pumping the primer before starting.

if pumping the primer solves the issue its definantly a low pressure issue.

[captain rednut]

low pressure pump

ill second a low pressure pump

[Mackesthlm]

What do you think is the reason it never happens during the first
run of the day?
Do you think it sucks air somewhere or that it is the pump that is bad?

After it stops I have to pump the primer to start it again. Then it runs fine for several hours. Until I stop for 30 min or so coffebrake again ;-) then it will often die a few minutes after I started it again.

[TownsendsFJR1300]

I think Rodbolt addressed it in post #2 exactly:


"test the low pressure fuel system.
try pumping the primer before starting.

if pumping the primer solves the issue its definantly a low pressure issue".

[rodbolt17]

typically what your describing is a failing check valve between the lift pump outlet and the lift pump inlet.
at speeds below 1200 RPM the lift pump cycles.
10 sec on 20 seconds off.
if the valve leaks the lift pump starts sucking air and the VST wont stay full and rail pressure drops and the engine dies.

just fixed a F225 yesterday same issue.
seems this fine Efuels like to corrode that valve.

that valve is supposed to maintain about 10 PSI at the VST inlet.

[TownsendsFJR1300]

Just another reason to use NON ethonol fuel!

Its cheaper at the pump than at the shop and NO down time/towing, etc....

[boscoe99]

Although Yamaha refers to it as a check valve in the Service Manual they refer to it as pressure relief valve in the parts catalog. Which is really what it is based on its function. When it comes to technical data Yam seems to be a bit confused.

2006 and Later F250BTUR Yamaha Outboard FUEL INJECTION PUMP 2 Diagram and Parts

The lift pump creates fuel pressure. Too much pressure if the outlet flow is blocked off, say if and when the vapor separator tank valve is closed. So, a relief valve is used which will allow fuel to circulate from the outlet of the pump back around to the inlet of the pump, and in so doing keep the pressure down. Down to whatever value the relief valve is rated for.

There does need to be some output pressure to ensure that fuel flows to the VST and that is what a valve in good condition does. If the relief valve were to fail open, then instead of fuel flowing to the VST to keep the motor running all of the fuel would simply take the path of least resistance and flow from the pump outlet to the pump inlet.

Fuel gets hot circulating through the pump. Perhaps the valve is operating differently when it is hot versus when it is cold.

Just as a test you could temporarily pinch the recirculating line mostly closed after you have stopped the motor. Start the motor after it has been sitting for 30 minutes and then see if it works normally and stops stalling. This would home in on whether the valve is failing or not. It is not an in expensive valve

Good luck and let us know the results.

[Mackesthlm]

Thanks for your ideas.
This spring, before tying the boat back in the water, I changed the whole
Fuel filter assembly located on the engine,
The old one had expanded and it was not possible to open the cup and change
the filter. I thought maybe it had been sucking air from
here. I also had an engineer check the Inside of the water separator which showed out to be in perfect condition.

After this everything went much better.
Last season it died everytime I started it the second time, but now only
A few times in several
Months.

I had already ordered the check valve as
as I was adviced.

Had it changed last week and since then I'm
Back to where I started. It now dies everytime
I start it for the second time.

It doesn't matter if I prime using the bulb before
starting the engine. After a few minutes it dies but after
Priming again it runs well for as long as I want.

Very strange. Maybe the problem is in the area around the
Water separator/check valve/ low pressure fuel pump
and they accidentally made it worse.


Any more ideas?

[rodbolt17]

idea?
use the Yamaha dealer locator function.
find a dealer in your area that employs a master tech.
take it there.
option 2 is splatter gun off the net until something actually breaks.
typically if a dealership has a master tech they or the tech, trained themselves AND purchased ALL the correct diagnostic tools.

kinda like my 2012 F150, about the only thing I can do is add washer fluid.