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Flushing fuel in a F90

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  • Flushing fuel in a F90

    I just pumped the old fuel from my boat after sitting a while and installed a new fuel/water filter.. I want to run the new fuel through the lines in the motor right up to the injectors before turning it over at all.. Looks like the fuel rail is held on with a couple 10mm bolts.Is it easy off and back on?. Can I just pull the rail off and pump the new fuel through it by cranking the motor with the rail off? Also I see what looks like a drain screw on the VST with a little drain tube attached.. Is that to drain and check if there is crap or water in the VST and do I drain that while the motor is turning and the pump pressure on the fuel? Thanks
    Key West 1720cc
    Yamaha F90TLRD mfg.05/04

  • #2
    Remove the drain screw from the VST. Use the primer ball to pump fuel through the system until clean fresh fuel pours from the VST drain.

    Replace the drain screw. Pump the primer ball to ensure the VST is full of gasoline.

    The fuel line from the VST to the injector rail has a quick disconnect fitting. Disconnect the rail at that fitting. Be prepared for gasoline to spray out. Maybe cover the fitting with a rag.

    Turn the key on. Fuel will be pumped from the VST to the fitting and purge the line there. That is about all that I would do unless for some reason the gasoline is really nasty. In which case you might want to remove all of the injectors and then use the VST pump to pump fresh gasoline out the injector ports.

    But to answer your question, it is easy to unbolt and remove the FI rail.

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    • #3
      if the fuel is real bad all filters and screens probably need cleaning/replaced

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      • #4
        Summary:I used a little 12 fuel pump to remove the fuel from my tank from the line on the fuel / water filter Then got to the "flushing fuel" new gas...I put the pump in line in the system for flushing but first with the pump off I drained the old fuel sitting in the VST and gravity drained clear fuel out but smelled bad after 8-9mos in the FL heat.. Then I turned pump on to push the new fuel through the new main F/W filter and used that little pressure on the system to the on engine F/W filter, then flush out the VST with some new fuel with the drain open. Then closed that up, turned off the pump and pulled the fuel rail.. I turned the pump back on and flushed the fuel rail 3-4sec only.. I had my new gas with some Yamalube RingFree in it right up to the injectors.. I'm glad I didn't turn the key before.. It started up and is running great .. and now ladies and gents might just be a new thread cuz I see my gauges don't light up.
        Key West 1720cc
        Yamaha F90TLRD mfg.05/04

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