[yammy5]

I have a Yamaha 225 EFI (year 2001) and a year ago I started having intermittent problems with the engine cutting out at WOT which would violently throw everyone forward every time it happened. The likely problem was a fuel restriction and the mechanic thought it was a sharp bend he discovered in our fuel line but even after repositioning the line, the problem persisted.

I searched this forum for an answer and found an engine with similar symptoms was fixed after discovering a clogged screen in bloat chamber & plugged filter going into pressure regulator. Another guy discovered the high pressure fuel pump filter screen at the bottom of the hp pump was plugged.

After the symptoms on my engine persisited (and got worse) I dragged the boat in for repair (yet again) and passed this info on to my mechanic but he found a different problem:

There are three fuel pumps on this engine and the middle pump had a 1 inch tear in the main diaphram preventing the pump from meeting the fuel demands of the engine at WOT which caused the engine to cut out. A simple fix ~ wish I new the answer a year ago. Hope this helps someone with the same problem.

[rodbolt]

your problem was one of using a tech that possibly did not have opposable thumbs, first thing to check on a 3.1, or any EFI/DFI motors is fuel pumps, then a simultaneous rail pressure and fuel system vacum test.
its very very rare it takes over 1 hour to test the systems on EFI/DFI motors.
while testing rail pressure and fuel system vacum you also have the winky blinky/laptop and the O2 sensor test harness installed. if the winky blinky shows no codes means nothing the ECU monitors is wrong and eliminates about 15 other checks right off the bat.
the low pressure pumps can be tested simply by squeezing the fuel primer bulb and feeling it.
next time look for the yamaha electrical and fuel system certifications on the wall at the dealership. not all techs have actual trainig and 5 star is a video course.

[wayneo99]

Rod Bolt I have read a bunch of your posts, they have been helpful. I am looking into the diphram tomorrow. As I am having the WOT problem.
I did notice that when the primer bulb is sweeezed it gets hard but with a little more squeeze it is as if there is not stop to the gas, the bulb continues to collapse in my grasp. Any indication to the diaphram status?

I assume they are the stock diaphrams as well.


2001 ox 66 225
thanks

[yammy5]

Well Rodbolt you are right again. Instead of $200 I should have handed our mechanic a banana. We took the boat for a 30 mile test run today and after 10 miles at 4500RPM the motor cut out and then continued to repeatedly cut out.

Obviously the problem is not fixed. The diaphragm issue was probably the result of the stress of the engine cutting out at 5000RPM so it was only a symptom of a different problem. I was wrong to assume the problem was resolved.

I think there may be a vacuum issue with the fuel and as you suggest there are specific tests that should be performed to test rail pressure and fuel system vacuum. When we were underway I pumped the ball but couldn't feel any fuel and the ball stayed flat for a couple seconds until I helped it back into shape. Perhaps a vacuum issue? What is the cause of vacuum lock in a fuel tank?

This is realllly frustrating. Our mechanic works for a large Yamaha dealer but I've never seen them hook a motor up to a laptop to run a diagnostics test. There are probably additional problems with the engine after the strain of repeatedly cutting out. For example I've noticed our speed is lower than it used to be at the same RPM. We have an extended warrenty thru this dealor so I felt it was a good idea to get the engine fixed thru them (although they haven't covered any of these repairs under warranty). Sounds like I need a new Yamaha certified mechanic.

[rodbolt]

dunno
but the vacum test is simple and can be performed while doing the rail test.
OX66 doesnt support the laptop but it does support the diagnostic test lamp.
anything more than about 4"Hg is to much, yamaha says 6"Hg on that engine but we find in real life its simply to much. could be your water seperator or anti-siphon valve, can also be your fuel draw tube has a filter that is clogged. can be as simple as mud dubber nests in the fuel tank vent line.
but keep running it lean and you will be posting about scuffed pistons.
look at the yamaha dealer locator site and try to find a dealership with a master tech in your area, like I say, 5 star is good but its a video course. my 5 star test took me 20 minutes, my master tech certificate took a bit more time.

[mikesea]

As rodbolt mentioned,a simple fuel tank vent can cause that problem if plugged.I have that problem right now.I tested by loosening my fill cap.Problem went away.Ive seen anti siphon valves corroded because brass and alum fittings wre used .That can cause trouble.These valves are at the tank.just adding my 2 cents. Good luck.

[snowmon]

any chance you just switched to ethanol blend fuel? if so i'll bet your issue is between the primer and tank. i had the same exact symptoms happen, (sx250tury). i have remote with yamaha 90 micron filter and crap was actually getting past that and engine mounted flter to vst filter. also replace low pressure pumps more often and removed anti-siphon valve from tank pick-up. i added a guage to remote filter bracket to help me with filter changes. i seem to have to keep an eye on vst filter & lp pumps way more often with alch in fuel.

[rodbolt]

ethanol fuels and the addendant problems are going to be a fact of life for the foreseeable future.
it creates all sorts of issues with fuel lines,needle valves and lift pump diaphrams.
makes the techs job even harder.
thats why we have fuel system vacum testers that dont require the hull to be in the water and diagnostic test lamps to look for trouble from items monitored by the ECU and test wheels and leakdown testers.
if used carefully and with a plan its rare to take over an hour for a diagnosis.
takes about 15 min on an OX66 motor to hook up the winky blinky,warm up the engine,while its warming up look at fuel rail pressure, do a spark and compression test, if it passes I just eliminated almost all the electrics other than the O2 sensor, takes another 15 minutes to use the fuel system vacum tester. if it passes I have usually isolated the issue to lift pumps or the VST.
to many techs simply seem scared to use diagnostic equipment and to many fail to be able to interpet what its telling them.
I cant tell you over the years how many MAP sensors I have seen replaced due to a mechanically defective IAC(ISC) valve.
tech said"the computer said it was bad" I asked what did the engine vacum actually look like and could you hear the IAC air screaming in the airhorn?
you have to understand how each engine subsystem works with the next if you dont your gonna hunt and peck a lot.
with 80+ an hour labor and the wild cost of some of these parts if the tech isnt well trained the custiomer and the dealership both lose.
you guys have no idea how embarresing it is to charge 1 hour labor and 326 dollars for the oil pressure sensor on a simple sensor failure.
the hour labor was about right as I had to run the bot above 4000 RPM for about 30 minutes before the alarm and RPM reduction set off.
the problem was the ECU showed to much oil pressure.
solution was to replace a defective oil pressure sensor. sensor is 326 sitting on the counter.
not near as bad as the 798 dollar medium pressure pump in the VST

[TheRock]

Yammy5 and I figured out our problem... in the end it was a clogged/stuck anti siphon valve at the top of the tank. Also the feeder tube inside the gas tank has an internal mesh screen filter, it was 90 clogged. We have replace the gas tank with a new custom built tank with no anti siphon valve ball/spring and our problem is 100% gone ! our engine sounds and runs like a different engine... it idles perfectly smooth, 5x the power now, our hole shot is almost instant and the boat comes up to plane in seconds.. as before it took a long time.. our max rpm are higher than we had before.. what a world of difference. Our problem was two fold, clogged in line feeder hose filter in the gas tank and a stuck anti siphon valve. Our engine has been running with a restricted fuel flow.. which in turned caused the fuel pump diaphragm in the engine to rip. Who knows what other strains/damage the engine had from a restricted fuel flow. So far our engine has never run so smooth until now. We removed the anit siphone valve ball and spring and removed the internal feeder hose mesh filter... we have a Racor fuel/water seperator filter as our main fuel filter.. no need for the internal feeder hose mesh screen filter... have it all open free flowing.

An anti siphon valve is only for when a gas tank is above your motor height.. I have no idea why a factory would put an anit siphon valve in a boats gas tank that is below your floor board ! no need for it.. take the valve of your gas tank and put it in a vise and knock the anti siphon valve spring and ball right out !! have it all open free flowing.. local mechanic here in town says that the anti siphon valves are the cause of allot of fuel pump failures.. now I can see why...

Hope this helps some one else with the same problem we had.



Amazing what a good fuel flow does !

[rodbolt]

the anti-siphon valve is legally required if any portion of the fuel system falls below the liquid level in the tank, otherwise .
and we are finding E-10 is bad for customers and frustratingly good for techs.
it also dissolves the polyester resins in the older Boston Whaler factory tanks.
ask me how I know.

[scottcmb]

Originally Posted by rodbolt

the anti-siphon valve is legally required if any portion of the fuel system falls below the liquid level in the tank, otherwise .
and we are finding E-10 is bad for customers and frustratingly good for techs.
it also dissolves the polyester resins in the older Boston Whaler factory tanks.
ask me how I know.

Jeez Rodbolt you just gave me a good picture of what it must look like inside the engine with the result of dissolved resin being combusted
plus also what it would do to EFI/DFI systems

[rodbolt]

the dissolved polyester coats everything in the carbs,venturies(both sides) intake track, valves,sparkplugs and most likly piston rings with a black tarry substnce, feels like resin that wasnt mixed properly and almost sets yet stays tacky.
luckily carb cleaner and combustion chamber cleaner seems to redissolve it.
yep its gonna get nasty here for the rest of the summer, my crystal ball foresees many popped power heads and lots of expensive fuel system repairs.