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  1. #1
    Seaman Apprentice
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    Default Overhaul Vapor Separator Tank

    1996 454 Magnum MPI with the VST systemEngine # 0F802536 Model # 4454118JTProblem: Hesitates over 50 mphHave taken the Admiral's and Commander's advice and have run the problem to the VST.Checked / Replaced- fuel/water separator filter- bad gas- antisyphon valveI want to replace the O-rings, Diaphragm, Float Kit, and maybe more in my VST. Having trouble finding the kits on the web. Any advice on where, and what to get to rebuild this VST? Lots of parts but no kits.Also, how often does the electric fuel pump (within the VST) fail on these?

  2. #2
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    Default Re: Overhaul Vapor Separator Tank

    Don S. Any input on this? Thanks

  3. #3
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Overhaul Vapor Separator Tank

    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  4. #4
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    Default Re: Overhaul Vapor Separator Tank

    I'm going to rebuild this Vapor Separator Tank with a float kit, diaghragm kit, and valve kit. How often does an electric fuel pump go bad and is fuel pressure which is consistent with the specifications mandatory? Manual says 34 - 36 psi but I'm getting around 31 psi.

  5. #5
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    Default Re: Overhaul Vapor Separator Tank

    Electric fuel pumps do fail. I can't say that I have seen a time or hours of use pattern. It is common to see one fail in a twin engine boat and the other engine will last years longer. Your fuel injectors are calibrated to put out an exact amount of gas for each pulse the ECM sends them. They cannot do this if the fuel rail is low on pressure. The engine will run lean at full throttle. If you are sure of the accuracy of your gauge and reading, then you need to find out why the pressure is low and correct it.

  6. #6
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    Default Re: Overhaul Vapor Separator Tank

    Having same problem as I did 7 years ago with a dirty screen in my vapor seperator tank. Does anyone know the trick to getting the screen off of the bottom of the electric fuel pump? I've pulled, twisted, etc. but I'm almost to the point of cracking the plastic.

  7. #7
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Overhaul Vapor Separator Tank

    If you are having the same problem, you need to clean the tank, and change fuel filters more often. As I recall on those, with the screen facing you, you turn it Clockwise (Not CCW like you loosen a bolt) about a 1/4 turn or less and pull it off.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  8. #8
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    Default Re: Overhaul Vapor Separator Tank

    That brings up a great question. Where are the fuel filters on a 1996 454 with EFI? I know of the screen on the fuel line intake, the fuel/water seperator and then the screen in the vapor seperator tank. Are there any more?

    Also wondering if I should fill the reservoir in the VST before putting the cover on it? The manual says to turn the ignition on for 2 seconds but don't turn over the motor. And then repeat three times. But it has a mechanical fuel pump in line before going to the electric puel pump that is located in the VST so what good would that do?

  9. #9
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    Default Re: Overhaul Vapor Separator Tank

    Simple question. When I put the new o-ring that seals the lid on the VST should I put it in as is or put something on it? (oil, bellows adheshive, etc.)

    Also, see last question above on fillling the VST upon installation. Could I put a little fuel injector cleaner in there also? Would go right to the injectors.

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