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  1. #1
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    Fuel and air rail testing

    this is a follow up from my Port Side Spark Plugs Black that i posted on 7/02/19 and last comment was 7/11/19. 1E001029 is the old serial # replaced power head with part # 8M0125790 or serial # should be 1B973744 or higher. gauge was not a liquid filed gauge so it was erratic bouncing from 105 to 95 Port side running . at shut off reading 92, 5 seconds later 90 ,10 sec. 90, 15 sec 89, 60 sec 89. when un screwed had a lot of fuel come out. Starboard when key was turn on fuel pressure was 105, when running bouncing from 115 to 100 , shutdown 92, 5 sec 90, 10 sec 90, 15 sec 89, 60 sec 89. fuel came out but no air when unscrewed . took out 1 spark plug on each side and put 80 lbs. regulated air in port side do not here any leaks , slowly raised air pressure to 95 and heard air going through . also port spark plug carbon foul and starboard good. had a little fuel and oil on lower unit . This motor had all 3 diaphragms replaced with only 17 hours on power head, now should be around 75 hours on power head. also in march i put a fuel pulse kit in , water separator filter , bulb and fuel line from Don, also new spark plugs gaped .042 - .044 . idling rough and dieing with lose of power . get worse each time out . 20190721_171128.jpg

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Kim- always best to pick up in the same thread if it's a related problem, for clarity.

    Really very difficult (borderline impossible) to accurately diagnose pressures without the correct type of gauges. Glycerin-dampened are best.

    IF your pressure readings were to be trusted, you have a sudden loss of fuel pressure at engine shutdown (indicating that you may have a tracker valve, fuel pressure regulator, fuel injector o-ring, high-pressure fuel pump sleeve, or other fuel leak).


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    #3
    yea i knew the gauge was crap, i will get it replaced with a glycerin filled and try again . thank's Don.

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    #4
    got new liquid filled gauge , port 85 with fuel coming out of schrader valve , starboard 95 with maybe small amount of air saw a couple of bubbles come out while taking hose off . no leak down on either side. still fuel on lower. should i check o rings first then pull all 3 diaphragm's . if so do you sell the tool to replace them.
    Last edited by kimclark; 07-28-2019 at 07:08 PM.

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    DON'T "Pull all three diaphragms"- there is no reason to, and odds of inducing a problem are high.

    Check the tracker valve FIRST. You definitely have a leak.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #6
    Okay will do that, will the tracker valve have a high pressure spring in it ?

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    #7
    no/ just did one spring is low press no spec tools needed/air reg and fuel reg are high need spring tool
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    #8
    Thank's Joe .

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    #9
    yea man
    .................................................. ...the scariest thing in life is the unknown ...................................

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    #10
    tracker valve looks good , pulled injectors out of starboard side all o rings look good also, what next ?

  11. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #11
    Nice talking with you today. Fuel pressure regulator would be the next most likely culprit (strongly recommend proper tool to reassemble, and must still use extreme caution so as not to pinch diaphragm).

    That tool you inquired about (889531) is currently on backorder.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #12
    Fuel pressure regulator was the culprit . air was good. i will be calling your shop Tuesday to get one, as far as the tool my local mech will let me use his. Thank's Don for walking me through this problem we really appreciate your shareable knowledge on BBC.

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    #13
    Thank's Don and Joe , changed Fuel pressure regulator idles good, no leaking fuel, and no fouled plugs.

  14. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #14
    Good idea to recheck the pressures after repair to make sure that the pressures are within tolerance (they CAN change when you install replacement components).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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    #15
    90 lbs. port, 100 starbord . maybe cheap gauge, but a 10 lbs. difference .

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    #16
    I’m having the same symptoms in my Opti 200, rough idle and fuel in air rail. Working on it now,I appreciate you folks discussing this in detail. Not trying to hijack,just thanks.

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    #17
    check TRACKER VALVE first
    .................................................. ...the scariest thing in life is the unknown ...................................

  18. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #18
    Quote Originally Posted by kimclark View Post
    90 lbs. port, 100 starbord . maybe cheap gauge, but a 10 lbs. difference .
    Better get someone with known-accurate instruments to check this. Those pressure are not correct (nor is the differential).


    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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