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  1. #1

    MSX 150 Fuel pump question

    Hey, gang:

    I have a question about the fuel pump on my MSX 150. I have been dealing with a broken fuel fitting on the top of the fuel pump. I broke it off, and fixed it with a threaded brass fitting. No problems with the repair, but I was reading through the tremendous amount of info K447 has written on the subject of some of the fuel pumps he's dealt with. Pictures were excellent reference tools, and they allowed me to do my repair with no problem.

    But in the images of his MSX 140, his fuel pump looks identical to the one on my 150 with one exception: All the images of K447's MSX 140 fuel pump show a short (about six inches) black hose with a brass fuel regulator near the end. Mine has no such hose/regulator in the pump at all. The brass hose fitting is there on the underside of the fuel connection complex, but it's empty.

    A couple of questions:

    1. Is this just a difference between the 140s and the 150s? The 150 has a fuel regulator on the return line fuel rail connection. Is this the 150's version of the one in the tank on the 140s? Are they performing the same function?

    2. Chalk my next connection up to paranoia, but the return line ends just inside the fuel pump under the fuel connection complex. It seems to me that if return fuel came through that hole, it would spray right onto the two wired connections to the pump. I don't know enough to decide if this is a problem or not. Supply gas comes up the hose and out of the pump, but return fuel looks like it will just spray all over everything as it collects on the bottom.

    I've tampered with nothing, haven even taken the pump apart, but I a little worried about that return fuel hutting the exposed pump connections.

    Can anyone set me straight?

    Thanks,
    FLN


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Don't worry about the exposed electrical connections. It may seem dangerous, but it is actually OK like that.

    There would only be a problem if those connections were badly corroded, which should not happen inside a fuel tank (since there isn't supposed to be any water in there).

  3. #3
    desperado's Avatar
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    The MSX150 operates at a higher pressure @ 43.5psi and incorporates a rising rate pressure regulation system that builds 1:1psi in relation to intake charge boost pressure. So when the turbo spins 15psi boost, the fuel pump delivers 43.5 + 15 = 58.5psi fuel pressure. The MSX140 has a fixed fuel pressure system operating at much lower pressure.

  4. #4

    Gte it.

    Thanks for the replies.

    Thread closed.

  5. #5
    Moderator beerdart's Avatar
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    Anyone know the volume/capacity of the 150 fuel pump?

  6. #6
    casey67's Avatar
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    Is there a stamping # on the pump ?

    The Polaris service manual spec is 3 bar + boost (43.5psi+ boost)
    What " +boost" is , I have no idea.

    The Bosch web site shows 2 pumps with a spec of 3 bar=

    12mm inlet fitting-8mm out = 130 liters/hour @ 3 bar
    14mm in-12mm out = 207 liters?hour @ 3 bar

  7. #7
    Moderator beerdart's Avatar
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    I haven't pulled the pump yet. Trying to see if the 150 pump will have enough flow to support the 4-tec with 50# injectors.

  8. #8
    casey67's Avatar
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    ??? Is the stock fuel pressure 50psi for the 4Tech

    The Polaris manual also claims injector type = Bosch EV-6E...... fuel injector spec= 12 ohm

  9. #9
    Moderator beerdart's Avatar
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    Stock 4-Tech is 53 psi. I will be installing an external regulator.

  10. #10
    Moderator beerdart's Avatar
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    Quote Originally Posted by casey67 View Post
    Is there a stamping # on the pump ?

    The Polaris service manual spec is 3 bar + boost (43.5psi+ boost)
    What " +boost" is , I have no idea.

    The Bosch web site shows 2 pumps with a spec of 3 bar=

    12mm inlet fitting-8mm out = 130 liters/hour @ 3 bar
    14mm in-12mm out = 207 liters?hour @ 3 bar

    The pump is stamped Carter 4E20M05

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