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  1. #1
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    Cool Merc 2.5 175hp Fuel Pump getting low voltage

    Merc 2.5 175hp EFI Lazer
    Fuel pump only getting 9.6 volt
    Battery cables on motor side have 12.2 volts
    Fuel pressure = 35psi with key on pump running.
    Motor fires trying to run for 1-2 sec then dies slow like lack of fuel/pressure. Help please.
    Connection at electric pump are good very clean.

  2. #2
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    mechanical pump?.. tried pumping bulb when starts ta die?.. whats pressure when motor start dyeing?.. is pump still runing when motor dies?.. is tha 9.6 reading + to - on pump or pump + to - on motor ground?
    Last edited by tlwjkw; 06-16-2021 at 09:15 AM.

  3. #3
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    Positive to neg. On pump is 9.6 pump still running when motor dies yes.

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    I'll try others

  5. #5
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    sounds like tha mech pump may need some attention....

  6. #6
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    I'll try hand pumping , and test psi while running with out my help then kinda get some info..

  7. #7
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    .........

  8. #8
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    Tried hand pumping bulb to help mechanical pump out no change.. didn't really ever start just hit and fired 1/2 sec

  9. #9
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    filter at bottom of pump?.. fuel in vst when it dies?.. 'bout ta run out of "computer ideas".. jus ta make sure its a fuel delivery problem ya might squirt some pre-mix inta tha open butterflies when ya crank it...

  10. #10
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    jus for questioning tha pump and/or driver circuit ta make sure they aren't doin' something stupid.. disconnect tha + and - at pump.. find a purple anywhere on tha motor and add it to + on pump.. add a block/motor ground to tha - side of pump.. this will by pass tha ecu driver circuit and supply a continuous 12+ volts to tha pump when key is on.....

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  12. #11
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    Quote Originally Posted by tlwjkw View Post
    jus for questioning tha pump and/or driver circuit ta make sure they aren't doin' something stupid.. disconnect tha + and - at pump.. find a purple anywhere on tha motor and add it to + on pump.. add a block/motor ground to tha - side of pump.. this will by pass tha ecu driver circuit and supply a continuous 12+ volts to tha pump when key is on.....
    Thats what it sounds to me, the fuel pump driver is failing or the two wires feeding the pump are bad. Like he said, send 12v to the pump direct and see if it starts. That pop and die is the motor trying to start too lean.

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    Ok I'll run 12 volt to pump directly then try starting. And also see wat psi is with full 12v when motor runs normal electric pump runs solid correct. Bc I know it shuts off with key left on past 10-15 sec. Just want to make sure it doesn't run then rest then run then rest..

  14. #13
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    goin' thru tha ecu it is supposed ta shut off after a few seconds unless tha motor starts.. by passed (switched purple hot and solid ground) it will run as long as tha key is on..
    Last edited by tlwjkw; 06-16-2021 at 01:28 PM.

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    This is a motor Keaten got from me. 175 efi that ran good but something let loose and destroyed a cylinder cracking the register to the bottom. I was not confident enough in my welding to make the repair so I had James Perry do the repair. He then replaced 2 sleeves, bored, decked, and cleaned the block ready for building. His work looked outstanding. Chris Carson cleaned injectors and supplied new reeds. Motor was assembled with 6 new standard bore pistons and metal caged bearings. I got ill (heart attack) and did not start motor. This is not Keaten's first rodeo so I figured it was OK to sell it without starting. Now I wish I had it back so I could get it going. My guess is also the driver so anyone with a digital ecu for sale or loan please let me know. This is my responsibility and I want it to be correct. We can certainly try the bypass but I don't want to have it that way permanently. Needs to be used as Mercury planned. Appreciate the help guys.

    Rock
    Team Junk

    No sparkling wiggles in here, only dump truck grinches.

    "Screamin Heathen"

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  17. #15
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    Quote Originally Posted by rock View Post
    This is a motor Keaten got from me. 175 efi that ran good but something let loose and destroyed a cylinder cracking the register to the bottom. I was not confident enough in my welding to make the repair so I had James Perry do the repair. He then replaced 2 sleeves, bored, decked, and cleaned the block ready for building. His work looked outstanding. Chris Carson cleaned injectors and supplied new reeds. Motor was assembled with 6 new standard bore pistons and metal caged bearings. I got ill (heart attack) and did not start motor. This is not Keaten's first rodeo so I figured it was OK to sell it without starting. Now I wish I had it back so I could get it going. My guess is also the driver so anyone with a digital ecu for sale or loan please let me know. This is my responsibility and I want it to be correct. We can certainly try the bypass but I don't want to have it that way permanently. Needs to be used as Mercury planned. Appreciate the help guys.

    Rock
    Dammit, now I wish I hadn't thrown those 3 I had away a few weeks back. I tossed 2 200s and a 175. I may have a 200 ECU left, do you know if that would run with a 175 porting and exhaust, or would it flood out?

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