VST tank overfilling. fuel coming out of vapour purge line into manifold

[caymanstu]

Thanks for accepting registration. Got a set of 300s that are at 1570 hrs and 10 years old. We changed hp fuel pumps and when we dropped boat back realised we had fuel pumping up through vapor purge hose into manifold. Disconnected vapor purge valve and it stopped. Switched vapor purge valve with one from other motor. Still pumping up through purge hose. Checked float in vst. Seemed ok. Any ideas what else to check for? Thanks ladies and gents.much appreciated

[Seaduck]

Could be bad needle and seat inside vst. Even though float looks OK it could be out of adjustment. I fought it for a year and got sick and tired of dealing with fuel still seeping through. Bit the bullet and bought a complete new vst. Motor has never ran as good as it does know. I hated spending that kind of money but after the results I'm glad I did. Good luck bud

[artdf175]

this has been discussed here before
one of the more common reason is the float valve problem is
it is out of adjustment so when it looks full the float valve has not closed off yet
suggest getting a motor manual and setting the float to the correct height first
Art

[caymanstu]

Thanks guys. We repulled everything. Cleaned and reset. Seems we got it right this time. We went a little easier on the screws holding the vst from the top half. Cleaned needles. Checked float. Running better than when we bought the boat. Thanks

[Afterhours bowfishing LLC]

I know this post is old but my 2013 DF250AP is having the same issue. I've replaced the needle and seat, adjusted the float several times, changed all of the fuel filters and installed a new primer bulb. I still get fuel coming out of the EVAP vent line. I read somewhere else it may be the pressure regulator in the vst tank or the low pressure fuel pump. Hopefully not as those are both pretty expensive.

[Murray]

Usually low pressure pump issues will cause fuel starvation issues. My understanding with the low pressure pump is fuel is supplied to the VST controlled via the float, needle and seat. You have ruled that out by replacing the needle and seat and adjusting the float. I would suggest you check the fuel pressure at the fuel rail. Should be 36psi. when pressuring up the pump and only drop to 28psi within 10 minutes. If the pressure regulator is shot your fuel pressure will be more than 36 psi.

[Afterhours bowfishing LLC]

Thank you for your response.

I have 42psi after the high pressure fuel pump while trying to crank the engine over or just turning the key on. Bleeds off to 34 psi after a few minutes. Also the EVAP switch seems to let fuel past whether it is plugged in or not. Think it is bad also?

[Afterhours bowfishing LLC]

The outboard does seem to start now either. It was running earlier this week but now it just cranks.

[Afterhours bowfishing LLC]

Is there a way to test the fuel pressure regulator? I just saw they were $100. I would rather not buy one if I dont have to.

[redlowrey]

Murray is right in saying that problems with the low pressure pump will cause starvation, the smaller engines have the low pressure pump bolted to the engine and can leak fuel into the crank case raising the level.
But not in your case you have an electric pump, nothing to do with the pressure reg, when ever you replace the needle and seat assembly replace the float, it is a prick of a job and you only want to do it ounce.

Compisat material floats get porous allowing fuel to pernitrate making them heavy, and hollow floats leak making them heavy too, and they lose buoyancy and don't control the pressure on the needle and seat allowing fuel to keep rising in the vst.

[Afterhours bowfishing LLC]

I'm not saying you are wrbuong. I thought the same thing because I've delt with that issue on atv carbs before but even if it had lost some of its buoyancy I would think I should have been able to see some sort of improvement when I adjusted the float. Also the float is hollow and I cant hear any liquid in it. I have the float submerged in gas for tonight and I will check it in the morning.

[Murray]

My service manual(2009 DF90A)states that fuel pressure should be approximately 36.3psi and bleed down to 28.4psi or less after 5 minutes. Suzuki uses the term approximately and then state 36.3psi which to me is a fairly exact number. A couple of questions come to mind and I don’t have enough knowledge to answer them. Are fuel pressure specifications the same for a 90 hp and a 300 hp? Is 41 psi too much if your fuel pressure specifications should be 36.3psi? Perhaps someone knowledgeable will chime in.

[Afterhours bowfishing LLC]

*******UPDATE********

I finally recieved all of my parts (damn covid)and have installed them. I have a new needle, seat, float, vst pressure regulator (still 42 psi), all fuel filters and O-ring/gaskets. $350 later and still have the same issue.
I unplugged the EVAP switch and it still shoots fuel out. I guess it's time to put it in the shop. Bowfishing season is officially over.

[redlowrey]

If you have a new float and needle and seat ass and set up correctly, it should hold its level. The only thing I can think of that would that would let fuel keep rising,, if the float was jamming, low pressure fuel pump pressure was too high, or crankcase pressure actually pressurizing the vst instead of venting, which should not be able to happen. As I said in my first post the pressure reg has got nothing to do with rising fuel in the vst.

Pull the purge line off the vst and make sure you feel it sucking when the throttle is opened and not blowing, and if you see fuel coming out the top of the vst with the hose off check the low pressure on the low pressure pump, if it is ok then you will have to pull it apart again.

[Afterhours bowfishing LLC]

I didn't think the float or the pressure regulator were the issue either but the mechanics are 4 to 6 weeks out around here so I had to try something. I've turned down $4000 worth of trips since my boat has been parked.

it will shoot a solid stream of fuel 3 or 4 inches high just by turning on the key. Once the boat starts it shoots a foot or so in spurts. Does the LP pump have a built in regulator? How could it get crankcase pressure?