Rodbolt 17 please help!!

[dorado42]

40 psi was under a load...never dropped

[mitch]

2005 F225TXRD Yamaha Outboard FUEL INJECTION PUMP 1 Diagram and Parts

have you tested number 25 and 40 as they also have a bearing on vst pressure as it releases vapour pressure from vst in to air silencer

[99yam40]

40 psi was under a load...never dropped

But was if while problem was showing ?
That is what you are looking for

When motor is running fine you know the pressures are OK

[dorado42]

OK finally spoke to someone who had the same exact problem as I have described...he had to go to THREE different mechanics to find his problem (I am fortunate to have friends on BOATS.NET forum)...he claims the problem was fixed by replacing the check valve on TOP of the VST tank.....

[rodbolt17]

all well and good, except for the FACT that the F200/F225 have NO check valves on the VST.
there is a valve between the VST inlet and the lift pump inlet.
there is a check valve at the airbox inlet.

the valve between the VST inlet and the lift pump intake is to maintain about 10 psi at the VST inlet and allow any excess pressure to bypass the VST.

the valve on the airbox is simply a VST vent.
it keeps most vapors inside the VST until enough vapor pressure forced vapors into the airbox.

[dorado42]

So my question would be do you think either one of these can be the cause for my problem....it definitely seems I am loosing pressure/supply of fuel in VST (I think) due to boat takes off and then falls off, the balls are soft and have to be pumped several times afterwards. They are both $100 each, so I would like to try one motor first and see if it works. Which one would be YOUR best advice? Yamaha calls them relief valve assembly, not check valves, sorry for the terminology error(LOL)!!

[rodbolt17]

myself?
I would carefully TEST the valve between the VST inlet and the lift pump intake.

but I think I actually suggested that a few pages back.

[99yam40]

...it definitely seems I am loosing pressure/supply of fuel in VST (I think)

So, apparently you have not monitored the pressures while the problem shows it's head if you just think it is

[dorado42]

ok Rodbolt17....in order to TEST valve I am guessing I will pull the valve off the boat. Hook a pressure gauge to the inlet side of the valve and apply air pressure SLOWLY to see if the valve holds 8-10 psi correct. I thought about using an old bicycle pump to apply air pressure slowly and steady enough to not exceed the 8-10 psi. Does this sound correct!! If it test OK...can I perform the same test on the valve on the top by airbox (VST vent)?? Does the valve on top also has a 10 psi rating. Thanks again for your help/advice!!!

[liliepad1]

Only thing im not getting is , on the portable tank problem is gone . would come down to a supply issue unless , said tank was above motor and siphoning fuel to motor . Motor is simply running out of fuel. Almost sounds like the lift pump is just air locking on warm restarts. Is the filter on the motor before or after the lift pump ? Pulling air there is possible i know the early filter cups got soft with fuel and were kinda hard to change , filters without replacing the cup its self which is replaced by a newer harder version .

[dorado42]

the portable tank did seem to fix the problem, that is why the entire fuel system has been replaced on one side (including low pressure pump). This problem is sooooo crazy; I am soooooo thankful for Rodbolt17 he has been AWESOME and sooooo helpful. I am hoping if I can determine a way to test the fuel filter assemblies on the motor I can determine if they are causing the problem. I will keep everyone posted....I have found many threads with similar problems but none of them share what the final fix was. Only had one guy share his FIX and he said it was one of the fuel filter assemblies but could not remember which one. He said he took it to THREE different mechanics, Rodbolt17 figured it out on the internet....

[liliepad1]

Could always bypass filter as a test with a fuel barb . What's the model number on your motor was wondering which style filter u had on the motor Nut type or one where the bowl screws directly into the filter base .

[dorado42]

I have Yamaha F225 TXRA....i have one motor was an old bowl and filter and the other one has a new filter, cup and base....also tested them for vacum leaks as well as checked all gaskets. I do not think i can by pass the valve because they operate on a pressure basis not just flow diection.

[rodbolt17]

ok, I will try one more time to explain WHY that relief/check valve is located between the lift pump intake and the VST inlet.

the lift pump is capeable of over 50 PSI as it has NO internal pressure regulator.

so as the lift pump cycles ON,only if the engine is running, there are TWO paths to suck something.

one is from the filter cup outlet.
the other is through the relief valve.

the lift pump should pull fuel from the FILTER then pump it to the VST inlet.
once the VST needle closes, IF the pump is still running, at about 10 PSI that valve breaks and allows fuel to bypass the VST and sent back to the lift pump intake.

if that valve LEAKS.

then pumps are quite lazy.

it would rather suck air past the valve from the VST than suck fuel from the filter and feed the VST.

yes Virginia its that simple.

typical symptom of that valve leaking.
1, after a ten min or so idle it shuts down and has to be reprimed via the primer bulb.
2, after starting and running a few minutes and the throttle is pushed hard the motor will either bog or try to take off then bog down.

at an idle you can watch the level of the filter cup go up and down as the pump cycles.

somefolks can actually hear the pump cycle.

below 1200 RPM the lift pump is ON 10 seconds and OFF 20 seconds all de dang day long.

so ya see Virginia, as that valve leaks a bit at low speeds it will allow air into the lift pump intake.
as this air gets mixed with gas and run through the pump it exits the pump as FOAM.

as gasoline COOLS the pump and FOAM does NOT cool the pump you have issues.

the VST doesn't like foam the lift pump doesn't like pumping foam and the longer it runs the worse the foaming gets until it simply quits.

a quick test you ask??
simply have a trusted helmsman, preferably NOT on your life insurance, run the boat in its normal stalling way.
verify you can REPEAT the issue.

then with the hood off and aforementioned helmsman, clamp off the line between the valve and the lift pump intake with a pair of needle nosed pliers and retest.

that valve body is made of aluminium, guess what Efuels EAT ????

however as an organic solvent or a nerve deadener, Ethanol is pretty dang good.

in fact my coke and Ethanol mix is a bit low right now.

[fuzzymaster]

Coke and ethanol! Are you serious Clark?