vst question

So I'm slowly narrowing down my problem. I think I ran out of gas or was very close to it and that might have been the original cause. I replaced the high pressure fuel pump and can hear it fire up on the first click of the ignition for 3 seconds. For some reason the gas is not getting to the vst.

When I pump the primer bulb the gas is flowing to the low pressure pump but I'm guessing it's not getting into the vst. When I depress the air valve on top and also open up the drain screw on the vst and pump the bulb I see no gas coming out. I will have to take apart the vst again to check this but it seems like no gas is getting into the vst.

I read about opening up the fuel rail valve, if there is pressure in my fuel rail would that keep the gas from getting into the vst? I thought that float valve inside the vst only shuts the valve when the gas is inside the vst, could that be the problem or is there something I'm missing?

The fuel primer bulb is okay.
The water separator inside the engine does not have water in it (the red ring is on the bottom)
Originally when I checked continuity on the fuel relay it tested okay.
The low pressure fuel pump should be okay, at any rate from what I'm reading it's mechanical and if I'm pumping the bulb the gas should be filling the vst.

Evidently I deleted the first paragraph:

The motor is a 2005 Yamaha f90 4stroke with about 500 hours on it.

Try pumping the fuel bulb until you feel pressure. Remove the fuel line to the fuel rail and have someone stand back there holding the fuel line over a mason jar or something. Then key the ignition only to the run position (not the start position) - when the HP fuel pump kicks on for those three seconds you should get a 3 second squirt out of that fuel line. That will tell you if you're getting fuel to the rail. If you're getting fuel to the rail, try putting the fuel line back on the rail again, re-pump the fuel bulb to resistance and then key the the ignition to the run position (not start) again to get that 3-second pressure build. Key it several times while someone holds a small screwdriver down in the schrader valve on the top of the fuel rail to open it (looks just like the air fill valve on a tire) and see if with a few keyings of the ignition and squeezes of the fuel bulb you get fuel to come out of that schrader valve under pressure when someone is holding it open. That will tell you if your getting fuel up through the rail to the top and will also purge all air/bubbles that may be in their.

Many thanks deepsea 21, I will try that tomorrow. If by chance there is no fuel getting to the vst as I suspect, what could cause the blockage upstream or downstream from the vst?

If you find you're getting fuel to the rail and up the rail to the schrader valve with hand pumping and keying the ignition to run the HP fuel pump my next guess would be the diaphram in the mechanical low pressure fuel pump has failed. Usually when that starts to go you'll find the engine starts "making oil" as fuel starts gradually flowing past teh diaphram into the crankcase. If the engine is "making oil" that's the #1 cause. It's on the back of the engine with 3 screws in a triangle. You can take it apart and check that diaphram and if it's bad you can replace just the diaphram - no need to replace the entire assembly. IF you go to SIMYAMAHA's website and look at the Fuel 1 diagram for your engine it's part #19.

Deepsea, I've heard of that before and I'll check my oil tonight as well. Wouldn't pumping the fuel primer bulb bypass the low pressure pump (if the low pressure pump had a problem)? The only reason I ask that is on my older honda 4stroke I had the springs in the low pressure pump fail, the only way that motor would run was to pump the bulb.

I was thinking that since you normally pump the bulb to prime the engine, the route was from the bulb to the fuel filter inside the cowling, then to the low pressure pump then to the high pressure pump and then to the fuel rail. Someone mentioned that there is a needle on that float that may be jammed and I will have to clean it out, I'm not sure how to do that because I haven't seen the needle yet when the vst was open.

I believe hand-pumping the fuel bulb should push fuel all the way through to the VST. On my F115 the float and needle valve is up inside the top cover of the VST that you took off. You may have missed it because when you take the cover off your natural instinct is to look down in the bowl where the HP fuel pump & filter is. My VST is an absolute PITA to get to on the F115 - first time took me about 3 hours to get to, second time about 1 1/2 - 2 hours once I found the right combination of extensions, sockets and ratchets to reach an absolute nightmare lower bolt on the intake. I was almost tempted to leave that bolt out when I put it all back together but, of course, I didn't.

Check out the parts diagram online for your model - It's under Fuel Injection Pump 1 - you'll see the little pyramid kind of shaped float shown up in the top cover of the VST and the needle valve it controls. It's possible the needle valve got stuck up and the orifice that it opens and closes got gummed up shut... especially if you are running fuel with ethanol in it and not using a marine fuel stabilizer ALL THE TIME.

I personally got so sick of fixing ethanol fuel problems that I now run only 100% gas even at the premium cost and I still add green marine Sta-Bil ALL THE TIME. My time off is limited so these days I prefer to spend it on the water instead of under the cowling every year. For the few extra bucks running 100% gas costs - it's a no brainer for me. If the hand pumping and keying can't deliver fuel to the rail and it's not making it into the VST tank that's another place to look. If it comes to that take that float assembly apart, pull the needle valve, and break out the jet-spray carb cleaner while cleaning the littel rubber tip on the top of that needle valve and the receiver where it sits up into in the float-up closed position.

And obviously, if/when you take that float and needle valve apart, do it over a large pan, white towel or something - you don't want some of those little parts to go flying off into nowhere you also own a VERY sensitive metal detector! Let me know how it goes.

Thanks deepsea. It looks like I'm narrowing it down, so I took off the intake silencer again and it looked like I had kinked a fuel hose. Once I moved it the VST is now getting gas.

The new aftermarket fuel pump however is not moving the gas to the fuel rail. I can hear the pump fire up (I couldn't hear the old pump fire at all before), but the engine would not start. When I took off the fuel line from the VST going to the fuel rail and turned the key, no gas was moving to the fuel rail. I tried the first click several times and never saw a drop of gas going towards the fuel rail.

Besides being a dud pump is there anything else I'm missing before I send it back and buy the oem yamaha one?

That VST tank takes a lot of fuel to fill. Pump- pump- pump with fuel bulb or when you have the VST tank off and open, fill it maybe 2/3rds full of fuel before you put it back on. That float and needle valve are at the top of the VST because the HP fuel pump is actually cooled by remaining pretty much submerged in fuel inside. A few pumps of the bulb won't fill the tank high enough in my opinion.

Thanks for all the tips deepsea. It turned out to be my high pressure fuel pump. That aftermarket fuel pump looked great and was well made but obviously something was wrong inside it, I almost wonder now that I'm thinking if they had wired it in reverse or something. I could hear the pump running but it never got gas to the fuel rail. I sent it back and bought the oem yamaha one from iboats, it was about 170. Pump came today and I installed it after work, when I clicked the key in the first position gas poured out of the hose leading to the fuel rail so I was excited. Sure enough once I buttoned that hose down the motor fired right up. Success!! I'm not sure what killed my old pump, it runs on 12v but it might normally run on less on the harness. It might have sucked up something when I was close to running out of gas but I have no idea what could have gotten by the racor and fuel filter and then the vst filter too.

Many thanks for all your help!! I'm off to chase tuna again this week!

Glad to hear you're running again and $170 sure beats a trip to Yamaha Service. I'll keep in mind that the aftermarket pump you bought presented problems. I remember when I had coils going in my car (V-8 with the coil-on-plug setup). I bought a cheap aftermarket set china for like $40 and the car ran for all of about 2-days before those coiks started to fail. Sent them all back and spent $170 on a set of AC Delco coils (also made in China but obviously to better specs as as I haven't had a problem in 3-4 years now from those). Sometimes we get what we pay for. - Tight lines.