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  1. #1
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    Optimax 135 Idle Help

    2003 Optimax 135 0T795533 384 hrs.
    New plugs, belt and water separator. Coils and compressions all checked out. Sometimes it will idle fine from cold start or hot. Sometimes it will not and/or kill when put into gear. But it doesn’t always do it. Since it’s not an always occurrence, could it still be a reed issue? Tracker valve? TPS sensor? Or any combination? Runs great when on throttle. Thanks for any help and advice.
    Last edited by MDean89; 05-29-2023 at 04:20 PM.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Primer bulb pumped firm before each startup?

    What plugs and what gap? Torqued with a TORQUE WRENCH?


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  3. Member
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    #3
    Thanks Don. Yes primed firm before each start up. NGK IZFR5G (5887) gapped at 0.034 (I wrote "new plugs", but they are actually one year old this week). Torqued to 20 ft/lbs. I do notice that between start ups, even within a minute, the bulb is not tight from previous priming. I pulled and inspected the tracker valve yesterday (bluegreen diaphragm material) and there were no tears or pinholes.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    Keep in mind bulb is only pressurized until the engine fuel pump begins PULLING fuel through it (at which time it comes under vacuum).

    Today's fuels vaporize in the fuel line at temps as low as 60F. Hence, pumping bulb before EVERY engine start is extremely important in warmer temps. Good habit year round.

    Plugs would be due for replacement (now).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

  5. Member
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    #5
    Appreciate it, I'll replace them and see what happens.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

  6. Member
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    #6
    Same symptoms with the new plugs. First cold start up idles but very rough. Shut it down, prime the bulb, re-start it, runs for a few seconds and dies. I repeat the process and on the third or fourth try then it idles. Put it in gear and it dies.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

  7. Member
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    #7
    [QUOTE=MDean89;13037584]Same symptoms with the new plugs. First cold start up idles but very rough. Shut it down, prime the bulb, re-start it, runs for a few seconds and dies. I repeat the process and on the third or fourth try then it idles. Put it in gear and it dies.[/symptomatic of fuel in air side of system fuel psi test will verify this
    .................................................. ...the scariest thing in life is the unknown ...................................

  8. Member
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    #8
    [QUOTE=JOE54;13038754]
    Quote Originally Posted by MDean89 View Post
    Same symptoms with the new plugs. First cold start up idles but very rough. Shut it down, prime the bulb, re-start it, runs for a few seconds and dies. I repeat the process and on the third or fourth try then it idles. Put it in gear and it dies.[/symptomatic of fuel in air side of system fuel psi test will verify this
    Getting gasoline out of the air side top schrader valve……..a pretty good squirt of fuel. Nothing from the bottom schrader.
    Last edited by MDean89; 06-04-2023 at 11:15 AM.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

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    #9
    there ya go , internal problem in rail-s
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #10
    Quote Originally Posted by JOE54 View Post
    there ya go , internal problem in rail-s
    Ok, anywhere I could start with to narrow it down? Is a pressure test still necessary if I already know fuel is getting into the air side?
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

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    #11
    i would look at tracker diaphragm first its the easiest
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #12
    Quote Originally Posted by JOE54 View Post
    i would look at tracker diaphragm first its the easiest
    Thanks.
    Last edited by MDean89; 06-07-2023 at 08:30 PM.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

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    #13
    Alright with the engine idling rough, I start unplugging injectors. All caused a rougher idle or killed the engine when disconnected Except for the middle one on the port side rail…..when I disconnected that one the idle smoothed out to great. I plugged it back in and rough idle starts again. Just a bad injector?
    Last edited by MDean89; 06-07-2023 at 09:43 PM.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

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    #14
    not necessarily swap direct injector with another cylinder see if problem follows it
    .................................................. ...the scariest thing in life is the unknown ...................................

  15. Member lpugh's Avatar
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    #15
    Agree with Joe on probable cause and verification. Time to flow test and clean all injectors.
    when you check the tracker valve be sure to fold it away from the center section evaluate better, all the around both sides.
    Thank You Leon Pugh

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    #16
    I was disconnecting and re-connecting the fuel injectors not the direct injectors. Would it still be a direct injector swap?
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

  17. Member lpugh's Avatar
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    #17
    Yes, do that first,
    Thank You Leon Pugh

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    #18
    ^^^^^^+1
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #19
    Ok I wasn’t confident enough to remove the rails to get to the direct injectors so I took a shot at what I could handle… I replaced the tracker diaphragm, spring and o-ring (no change), replaced the port fuel/air regulator diaphragm, spring and o-ring (no change), replaced the port air regulator (no change), all done with the rails left in place. After inspecting that fuel injector I pulled in the beginning I noticed the little screen filter on the injector itself was completely gone. I replaced this fuel injector and idles like a champ now. Possible the little filter screen disbanded and plugged the fuel injector?
    Last edited by MDean89; 06-13-2023 at 06:45 AM.
    2003 18' Xpress H56, 2022 Tohatsu MFS140 / Serial #071184BB

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    #20
    dout it contaminants let in inj from no filter yes id have to pull anther and see if any more are missing , are you the original owner , has anyone repaired these rails , so you replaced all 3 diaphragms and never loosened rails from heads (left in place ) wow
    .................................................. ...the scariest thing in life is the unknown ...................................

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