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  1. #1
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    Apr 2019
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    Denver, NC
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    Looking for some ox66 help

    Hello everyone. I haven't posted much on here but I've been following and reading for quite a while.
    I have a 200 3.1 ox66 that I'm having some issues with. I just rebuilt it and after getting everything back together the motor runs fine until it warms up then quits and wont restart until given some time to sit. After it dies it will try to restart for a few tries then just spin over. I have 35psi on the fuel pump and I've checked my ignition system and it's all good. I also checked compression just to be sure and it's good. I've been running to boat on an aux tank during the break in and noticed the first time it happened that the tank wasn't venting and was sucked shut. I opened the vent and even swapped back to my onboard tank and still nothing. I'm just looking for any suggestions for things to check out I'm stuck.

  2. Member
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    Apr 2019
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    #2
    Well update from my troubleshooting today. Got engine running and whenever it cut off I had some fluctuating voltage on he fuel pump. Pressure was corresponding directly with the voltage fluctuations and bounced around with the motor running rough until finally lost it all together and engine cut off. After doing this I can key off and back on and the fuel pump will turn right back on and build 35 psi but engine wont crank. I sprayed a little bit of starting fluid in the intake after it died just to double check ignition and she fired up but would not stay running.
    I've read a few posts on the main relay which feeds the fuel pump and I know that they go bad but the pump turns right back on after engine dies and builds pressure.

  3. Member
    Join Date
    May 2015
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    Zwolle, LA
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    #3
    I have the ox66 3.1 225 but have never had those issues.
    Bill Perry
    Zwolle, LA (Toledo Bend)
    bpicinc_2000@yahoo.com
    2001 ZX-250 VMAX 225. HDS-9 Carbon, HDS-7Carbon, 3D Sonar, HB 998c hd si, Active Target, MG Tour Pro 36v, 12" Slide Master
    USN, USS Newport News CA-148

  4. Member
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    Mar 2018
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    Cincinnati, ohio
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    #4
    Quote Originally Posted by 01BCproguide View Post
    Well update from my troubleshooting today. Got engine running and whenever it cut off I had some fluctuating voltage on he fuel pump. Pressure was corresponding directly with the voltage fluctuations and bounced around with the motor running rough until finally lost it all together and engine cut off. After doing this I can key off and back on and the fuel pump will turn right back on and build 35 psi but engine wont crank. I sprayed a little bit of starting fluid in the intake after it died just to double check ignition and she fired up but would not stay running.
    I've read a few posts on the main relay which feeds the fuel pump and I know that they go bad but the pump turns right back on after engine dies and builds pressure.
    Ok if it's shutting down after warm that could either be thermostats sticking or if you're pisser is super hot then your water pump isn't sufficiently cooling down motor. Motor then will shut down to cool. Any alarms? If you're running it in on muffs in the driveway then it doesn't get the same pressure as on the lake under full pressure, in return overheats. That's my two cents from a Non- marine mechanic.

  5. Member
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    Mar 2018
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    Cincinnati, ohio
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    #5
    May be primer bulb too!

  6. Member
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    Apr 2019
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    Denver, NC
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    #6
    Quote Originally Posted by JJ200sx View Post
    May be primer bulb too!
    Thanks for the reply. I just rebuilt the motor and replaced both thermostats when putting it back together. I've been super busy at work this week haven't had much of a chance to troubleshoot but I did notice that I had the vacuum line from the pressure regulator connected in the wrong place. I ran it for about half an hour one afternoon this week and it stayed running to whole time and never cut off. I'm going to lake test it today and see how it does.

  7. Member
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    Mar 2018
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    Cincinnati, ohio
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    #7
    Well that's good you seemed to find the source! Good luck on the water with the test!

  8. Member
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    Jan 2018
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    White Lake, Michigan
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    #8
    another thing to check is the fuel pressure resistor, ohm it out make sure it’s in spec, that will give you funky voltage readings on the pump

  9. Member
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    Sep 2014
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    Dallas, TX
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    #9
    Did you also replace the LP pumps? One thing you could check is that as soon as it dies, turn the key off and open the screw on the VST to see how much fuel is there. Sounds like it is running out of gas, so choices could be: LP pumps, fuel pump relay, restriction on HP pump, HP pump.

  10. Member
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    Apr 2010
    Location
    Canton, Ga
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    #10
    Quote Originally Posted by Michiganfishing View Post
    another thing to check is the fuel pressure resistor, ohm it out make sure it’s in spec, that will give you funky voltage readings on the pump

    HAve you every had one go out? I've been having lots of trouble with mine, and based on what you said I decided to check mine. Mine is reading anywhere from 0.2-0.5, and bouncing around almost constantly. Was wondering if I should replace it. My yamaha book states 0.53-0.57 is spec.

  11. Member
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    Apr 2019
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    Denver, NC
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    #11
    Well issue resolved it was the vacuum line. As far as the fuel pump resistor mine is also out of spec. I read somewhere that the cdi only uses it during a certain rpm range. From looking at the schematic in the manual I'm not really sure how it bypasses it and I'm really not sure the function of it. Looks like it's in series with the pump so I'm assuming it's to drop voltage. Even then .53ohms doesn't do much in the way of dropping voltage.