Merc 4.3 fuel pump power/wiring, carb ?

Discussion in 'Gas Engines' started by wood45s, Oct 16, 2017.

  1. wood45s
    Joined: May 2017
    Posts: 10
    Likes: 0, Points: 1
    Location: ga

    wood45s Junior Member

    Merc 4.3 fuel pump power/wiring, carb ?
    1995 Starcraft Islander 221 recently purchased.
    It runs good once cranked. It’s a little hard starting when cold, but cranks good after the first start. I drip a few drops of gas in the carb and cranks immediately when cold. Choke is closed. Carb is a Weber 4barrel. With it not running and I take the throttle cable off and pump the throttle lever there seems to be no extra gas squirted in the throttle bores. Is this normal? Or maybe I have an accelerator pump problem? Merc manual says the pump should have 7/16 inch stroke. I’ll have to check that tomorrow.

    Concerning fuel pump – the Merc book shows a purple/yellow wire connected to the starter solenoid along with the yellow/red wire. The purple/yellow wire is not hooked up. I’m not clear on this, but thinking maybe that purple/yellow wire needs to be hooked up and provide power to the fuel pump while the starter is activated? I don’t yet fully understand the wiring between solenoid, slave solenoid, starter and ignition switch.

    Thx,
    wood
     
  2. gonzo
    Joined: Aug 2002
    Posts: 13,309
    Likes: 323, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Are you saying the mechanical pump was replaced by electric?
     
  3. wood45s
    Joined: May 2017
    Posts: 10
    Likes: 0, Points: 1
    Location: ga

    wood45s Junior Member

    Never was a mechanical pump - it has oem electric fuel pump. there's not even a mount provision for mechanical pump on the block.
     

  4. gonzo
    Joined: Aug 2002
    Posts: 13,309
    Likes: 323, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    It may have a bypass to make priming the carburetor easier. There is a safety switch connected to the oil pressure. It shuts off the pump when there is no pressure. The double solenoids in Mercs can be confusing. The bypass wire is often hooked up to the solenoid at the starter; assuming you still have an original type. It should have two big connectors and two little ones with either studs/nuts or push connnectors. One of the small ones goes to the solenoid, and the other to the fuel pump.
     
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