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

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  • #16
    What should my pressure be on my low side? Does anyone know if the LP pumps are rebuild able? Cheapest I found is $450. Ouch.

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    • #17
      Has anyone used Quantum fuel pumps or should I go with factory if I end up having to buy one? Quatum is $349 and ships out asap. Factory is $400 + and will be 7 to 10 days do to COVID-19.

      I really appreciate everyones input. Still very frustrating though. Lol

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      • #18
        The purge line should have negative pressure on it when the throttle is opened and the solenoid activated and vent fuel vapors, check and see if that is what is happening. I would think anything over 8 psi the float would have trouble controlling, if fuel comes out of the top of the vst with the purge line off, and the fuel pressure is 8 psi or under, the problem is still in the vst.
        I have no specs on your engine and I am not sure.

        I know later engines have a PRESSURE RELEIF VALVE ON THE LOW PRESSURE SIDE OF THE SYSTEM AT THE VST, if that was stuck and the fuel pressure COULD NOT BLEED OFF, it would be way to high for the needle and seat and float to control. Don't get confused with the high pressure regulator inside the vst.

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        • #19
          I agree with 8 psi. I've blown on the fuel line and operated the float to see if it was holding. I'm not sure what pressure in able to apply but I know it was enough I damn near passed out. Lol.

          The vent off the vst has fuel coming out when I turn the ignition on and the LP pump is on. Once a crank the engine over it starts spurting from the vent line port. As of right now I haven't been able to really get the engine to fire up to see if it has a vacuum. I'm guessing because there is raw fuel in the intake plenum since that's where the purge line is sending the fuel. It did fire once yesterday evening for a second but I killed it because it was still shooting fuel everywhere. Now it just turns over.
          I've had suspicions it has been the LP pump all along but I dont know enough about how the system operates to say that was it. And its $400+ dollars.

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          • #20
            Look for an external relief valve in the low pressure line before you condemn the pump, put a gauge on it and see what the pressure is.

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            • #21
              I have been thinking about this issue for some time. Artdf175 discussed the VST being the culprit in the 1st part of thread. Caymanstu was able to solve his problem replacing parts. Bowfishing, I can't remember what you worked on inside VST. However, even if you cleaned and verified float the fact is fuel is coming out of the vent side. Whether the fuel pressure is perfect or not, the only way fuel comes out is the needle valve allows it. It can't overfill if fuel doesn't get into it (VST). As for 2nd engine being starved I believe most of the fuel pressure is lost with with the 1st engines VST issues. If it were my engine, I'd bite the bullet and buy another VST or take it to the dealer. When you consider dealer cost 4 or 5 hundred bucks for new VST it's a drop in the OB motor sea.
              Too many times I have cleaned parts and reinstalled only to discover I still have issues. If I have missed a point made by you bowfisher or other posters please forgive me.
              Last edited by briscoe; 10-18-2020, 11:00 AM.

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              • #22
                So I was able to get my fuel pressure gauge on the outlet side of the low pressure pump. When I turn the key on it quickly hits 70psi and falls to zero after a few seconds. I'm thinking that's an issue. I don't know of any needle and seat that can hold that kind of pressure.
                I ended up ordering the Quantum brand fuel pump because it had a lifetime warranty and it was cheaper but it has the wrong wiring connector. ‍♂️‍♂️Guess I should have spent another $100 for the Suzuki one.

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                • #23
                  No needle and seat could handle that pressure, but I still think that there would a relief valve in the low pressure line that you would only need to replace. In boat parts it looks like they are calling it a check valve 73$ pull yours off and have a look.

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                  • #24
                    I see that now. I removed and cleaned that. Didn't know that was a check/pressure regulator. It didn't seem to have any restriction when I blew through it so you may be right. Ordered one from Crowley's marine for $65. Should be here Thursday. I hope.

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                    • #25
                      Originally posted by Afterhours bowfishing LLC View Post
                      I see that now. I removed and cleaned that. Didn't know that was a check/pressure regulator. It didn't seem to have any restriction when I blew through it so you may be right. Ordered one from Crowley's marine for $65. Should be here Thursday. I hope.
                      '''''''''' That's right, but you would have to cover one end and then blow and it would take about 10 pounds to blow it off its seat,

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                      • #26
                        New check/regulator installed and stall have an issue.

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                        • #27
                          Have you got it connected the right way around

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