2006 F225 fuel issue

[Hooked Up]

99yam40, the high pressure stays right around 40psi the entire time. Thats what has me stumped, I know fuel feed/ availability isnt the issue. Just not sure what to check next without the having a diagnostic system. I think I will have to accept defeat and take it to the mechanic.

[boscoe99]

Why not fix the known issue and then see what happens?

[Hooked Up]

boscoe99, When I used the low pressure gauge from a 1gal external it shows between 4 and 6 hg. When I connect to the boats fuel tank, its at 2Hg. When connected to the lp pump output its 10 to 12 psi. The shrader on the hp side says 40psi spiking momentarily to 45psi when I 1st crank the engine. These readings are in line with everything I have seen.

i dont know what know problem you are referring to. I know the vst is filling because with the clear tube installed to check for bubbles, I could feel the pressure in the recirculation line after to vst float stops the flow of fuel into the vst. I also dropped the vst a 2nd time to verify the vents for the vst were not blocked and it was full of fuel. If the vst is full, and the pressure is generating...what next?

[boscoe99]

This is what is next.

"I think I will have to accept defeat and take it to the mechanic."

[fairdeal]

well, we got started off, from your first post, on the tangent of how the VST is kept full,

But as 99 has observed,
if you see are seeing a steady ~40 psi on the fuel rail at the moment that the engine dies -

IMO that excludes the theory that the VST has "run out of gas"

and points to some "electrical" issue

(and if the pressure is still on the rail after the engine stops - excludes the HP pump as the problem)

[panasonic]

What next is are you losing the ignition after thirty seconds or are you losing the fuel delivery....the injectors stop firing?

[99yam40]

since Yamaha does not have different sounds for different things, there is no way to identify what the horn means unless the gauges show something or diagnostic equipment can see something going on.

I wonder if he is loosing electrical power to injectors and/or ignition.
Would that sound the horn?

[rodbolt17]

no, but if you lose an injector ground the ECU will store it.
wont say which injector but it will store an injector code.
the only tone difference in a yamaha horn is some of the late model V6-V8. the horn will give consecutive beeps for water detect.
the Schrader valve for monitoring rail pressure is on the port rail not the VST.

[Hooked Up]

As follow-up, the problem turned out to be the water pressure sensor. It had failed, and was allowing water to seep into the harness through the sensor. This threw codes for oil pressure, TSP and a few others.

[zenoahphobic]

As follow-up, the problem turned out to be the water pressure sensor. It had failed, and was allowing water to seep into the harness through the sensor. This threw codes for oil pressure, TSP and a few others.

Interesting, an example where a device that is supposed to help in reliability, actually caused reliability issues.

[panasonic]

Glad you have it fixed and came back to let folks know what it was...many don't. How did you find it?