vst question

[c-level]

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.

 

[99yam40]

seeing that no one but you knows what motor you are talking about
and that it seems from what you have stated, you have taken the VST apart before for some reason.

My guess is the needle and seat is not opening due to something you did to the system.
What that is is hard to say as we do not know what all you were doing in there

 

[c-level]

That's my fault for not proofreading my work, I had somehow deleted the top paragraph.

The motor is a 2005 Yamaha f90 4stroke with about 500 hours on it. Originally I think I was very low or ran out of gas because I was at idle and the engine stalled. I added 5 gallons but I could not hear the high pressure fuel pump priming for those 3 seconds during the initial first click of the key. I have the shop manual and pulled the fuel relay and checked it for continuity and it was good so I assumed it was the high pressure pump.

I ordered a new one and installed it, it wasn't too hard on the f90. Now I can hear the high pressure pump hum during that three seconds when the key is clicked but the motor still does not run (it will sometimes cough and turn over so I have spark), I tried to drain the vst and very little dribbled out. I also pumped the fuel bulb and it was hard but it seems like no gas is getting into the vst. When I've read all the threads there isn't a whole lot about the vst remaining dry.

 

[99yam40]

did you depress the shrader valve on VST to let air in so it could drain?
you might want to open the VST up to make sure there is no fuel in there.
if no fuel the pump will not last long. needs the fuel to cool and lucubrate the pump

guessing it has good spark in not the best way to troubleshoot.
an inductive timing light(or a spark tester) is simple way to see if there is good steady spark to individual plugs, you even use it to see if timing is correct

 

[c-level]

Thanks 99yam40. Yes I depressed the shrader valve on the VST to drain it while I opened the drain valve, there was almost no gas in there. I'm not sure what the problem is flow wise, tonight I'm going to start tracing the hoses from the low pressure pump (I saw gas come out of that hose when it was loose and I was pressing the primer bulb and see if there's some sort of blockage going into or out of the VST.

I agree about the spark, I just know that I have to get gas in the VST before I start checking the spark. From what I've heard the VST has to have about 1/2 or 3/4 of it's tank full is that correct?

 

[99yam40]

should be filled to where the float closes off the needle into the seat, which I believe would be close to the top of tank

 

[c-level]

It looks like I'm narrowing it down and I started tracking the fuel route. 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. Just in case I ordered a oem yamaha pump and it should get here wednesday. Is there anything else I should look for?

 

[c-level]

Well I'm glad that's over. 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 hunt tuna this weekend!