Fuel starvation yamaha f225

[99yam40]

I would think monitoring fuel pressures would lead you to where the problem was.
if the lift pumps or any other pump did not have any fuel to pump you would see that.
If the check valve does not solve the problem, look at the pressures and see if the pumps run as they should

[marchmadness]

Ok I just installed a new vst check valve ran the boat sat for an hour and it died. This time I never got above above 1300 rpms,. I opened up the vst tank and only an ounce of fuel came out. The air vent on the air box had fuel in it . So I have an empty vst tank that did not refill.

[marchmadness]

Also the engine mounted filter has fuel in it we squeeze the ball and it won't get hard

[marchmadness]

Today I changed the vst relief valve assembly. Started right up and I noticed I had an increase in idle rpm. Went out ran shut it down. After an hour started right up started idling out never made it above 1300 rpms died. I opened up the vst tank drain and only about an ounce of gas came out. checked the air box vent there was a small amount of fuel. I waited around another hour ,motor cover off. I pumped the fuel ball while turning the motor over . took around four times to start. ran it back to the dock.

[pstephens46]

Follow the advice on checking the pressures as suggested.

[marchmadness]

what I don't understand is why does this only happen after I shut it down.When I restart, the lift pump should pick up the fuel and fill the vst tank

[fairdeal]

I have measured the volume of the VST on my F225TXRD, it holds ~ 9 ounces.

(although IIRC I used the provided Schrader valve so that it could fully drain)

IMO if there was actually only "about an ounce" of fuel in your VST
there is no need to measure fuel rail pressure -

you won't have fuel rail pressure if the pump doesn't have fuel to pressurize.

The fact that "pumping the bulb" gets you going, confirms that there is a problem keeping the VST full.

Either fuel is not getting in there while the engine is running or its excessively evaporating when you are stopped.

[marchmadness]

I am going to walk away for a day or two. The next time I'm going to go over every inch of the vst tank . Like rodbolt said about a leak still seems likely. I was wondering how that fuel cooler works ? should I start a new thread?

[99yam40]

as you said the lift pump should fill the VST.
does the lift pump come on as it should?
does it show pressure?

the cooler should keep the fuel from over heating while the motor is running,
when motor is not running water is not flowing

[boscoe99]

I have measured the volume of the VST on my F225TXRD, it holds ~ 9 ounces.

(although IIRC I used the provided Schrader valve so that it could fully drain)

It makes a big difference as to the quantity of gasoline that drains from the VST if the Schrader valve is opened or not.

I suspect the OP did not remove the air lock by opening the valve. But...

Now what I want to know is why you did not measure the amount of gasoline drained from your VST to a precise value. That is unlike you. I would have expected you to report that it held exactly 4,320 minims. Also, to the nearest nanosecond how long it took to drain the gasoline to the last drop.

[boscoe99]

what I don't understand is why does this only happen after I shut it down.When I restart, the lift pump should pick up the fuel and fill the vst tank

Hopefully you can find the precise situation where your problem occurs so that it can be duplicated. Over and over again.

When you know that the problem can be duplicated then try to test a few things when it happens.

Install a fuel pressure gauge to the Schrader valve. Turn the key on. Do you see rated fuel pressure?

Start the motor. Does the fuel pressure reduce somewhat but then hold steady?

Let the motor idle for a minute of so. Does the fuel pressure hold steady?

Does the lift pump run for 10 seconds out of every 30 seconds (10 seconds on/20 seconds off) while the motor runs at an idle RPM?

As the throttle is advanced watch the pressure gauge. Does the pressure increase as the throttle is opened? Does the engine stumble or refuse to come up on power?

[pstephens46]

Real close to a solution here.....

[marchmadness]

ok here we go the final solution. I removed the vst pump today and I believe the gasket was leaking ( between the housing and pump) took everything apart and cleaned it. I checked the lift pump and it was running a perfect 30 sec cycle. I ran the boat and let it sit for twenty minutes. I would have liked to get a better test but the weather got nasty. So I'm not 100% that's its fixed but I feel confident. My idle came back down to 7k. So it seems it was a combination of the relief valve and the vst gasket.

[99yam40]

My idle came back down to 7k.

700 maybe instead of 7K

[marchmadness]

sorry that would be a little high lol