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  1. #1
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    Question Diagnosing fuel/air problems

    2011 Optimax Pro XS - In service date Jan/2012

    Engine# IB861903

    287 hours
    Tracker Valve maybe 30 hours. R
    ebuilt the pulse pump, replaced tracker valve, cleaned out the VST, replaced all the fuel lines last year all at the same time.

    New plugs ran once.

    Same engine in another thread, but thought for clarity I'd start a new thread.


    Problem is rough idle, almost knocking, down on power, doesn't want to come up on pad. Will... but last time out it took 2~3 tries. NOT going back on the water till it's fixed.

    First diagnosis by a local shop, NOT a Mercury shop (Yamaha/Suzuki dealer): Air in fuel rail, fuel in air rail, #4 running hot. The owner at this shop is a good kid, he's helped me out reading the ECU and doing an oil pump prime for me for free. Then looked at it 2 weeks ago for free as well. Good kid, but not equipped to dig into the Opti. They sell mainly pontoons.

    I have the shop manual, and do all the work myself that I can possibly do. Been working on engines since I was a kid picking up races in the Shoney's parking lot in the early 70's.

    Bought the Merc air/fuel gauges, as well as the tool to replace the air and fuel diaphragms, even a Mercury injector pulling tool. Along with a vacuum gauge and compression tester. What can I say... a man should have the right tools to do the job.

    Today first diagnosis:
    Pressurized 80# air to the port side rail. Didn't hear any leaks, especially around the compressor. Depressurized starboard fuel rail via Schrader valve nothing came out. Tried to vent air rail (port side) fuel spit everywhere. Like an IDIOT I didn't have my safety glasses on. ALMOST took it in the eye (got an earful though).

    Decided to be smart and hook up these newfangled air/fuel gauges and vent the SAFE way.
    System pressurized, fuel comes out air rail.

    Cranked it up:
    Air pressure 92~94 (didn't have my reading glasses on).
    Fuel pressure 112~114. (seems a bit high)

    Vented both sides in short bursts via the gauges while it was idling, engine would sputter as expected, and recover fine. Idle is rough though and it's knocking (detonating?).

    Air rail spitting fuel.

    Pressure after shutting down:
    0 seconds, 92 - 112
    5 seconds, 92 - 110
    10 seconds, 88 - 100 maybe
    15 seconds, 86 - 100

    1 minute later 82 - 82

    (I'll have to record these better tomorrow, no glasses, and getting dark today.)

    I can get low pressure fuel readings and vacuum at the pulse pump tomorrow hopefully. I'll also get air pressure, fuel peak pressure, and both air and fuel volume readings per the manual. Will also get cold compression readings, (hot maybe, but it's really skippy sounding).

    Don told me how to check for a leaky fuel injector in the rail (before I'd read the procedure in the manual) so I'll get that done FOR SURE. Easy enough to stick a piece of paper behind the rail and look for 'spitting'.

    Seems it's pointing to fuel injector #4 having leaking o-rings (because it's obviously skipping, and via infrared running hotter, and the plug is 'sooty' after not an hour run time). Either that AND/OR the fuel pressure diaphragm, especially with 20~22 pounds differential.

    I'm thinking with the pressure differential the tracker valve may be in good shape. As noted above, it has maybe 30 hours on it. Perhaps its 'holding' the air pressure fine, but the fuel is high from either the leaky injector, and/or the diaphragm, which it's also holding.


    Would it help to run 90# air to pressurize the system and listen for leaks. *Considering the specs call for 92 air - 106 fuel.*






    Later,

    Dixie Chicken

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Specs are 94/108 (+/- 1 psi).

    Swap gauge connections and make sure you don't have a gauge reading high.

    Not going to make much difference supplying 90 psi... if it doesn't leak at 80, it probably won't leak at 90.

    Note: Any AIR LEAK will result in FUEL in the AIR SIDE. Your above comments indicate no air leakage at 80 psi.

    Check those o-rings on #4, and if they are good, check the pressure regulator diaphragm.


    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
    Quote Originally Posted by EuropeanAM View Post
    Specs are 94/108 (+/- 1 psi).

    Swap gauge connections and make sure you don't have a gauge reading high.

    Not going to make much difference supplying 90 psi... if it doesn't leak at 80, it probably won't leak at 90.

    Note: Any AIR LEAK will result in FUEL in the AIR SIDE. Your above comments indicate no air leakage at 80 psi.

    Check those o-rings on #4, and if they are good, check the pressure regulator diaphragm.
    Thanks Don!

    Lumbar L5~S1 going out again on me has me hobbling around the house making weird noises. That along with monsoon rains and NOW... 34° out made it impossible to get to the boat this week.

    This weekend:

    1: I'll reverse the gauges to verify the pressures.

    2: For snits-n-giggles I'll pressurize it to 90 PSI and take a detailed listen to everything in the system.

    3: Absolutely have fuel in air side, so I'll pull that rail this weekend (probably pull both while I'm at it) and do what you and I talked about with the piece of paper, "hint hint"

    If it's what we think..... you'll be getting a call ASAP from me on either the diaphragm, O-rings, or both. Found the guide tools for the O-rings on <EDIT- Read Announcements> pretty cheap, I'll have them here by Monday.
    I also bought the Mercury tool for replacing the diaphragms, so feeling good about being able to handle that.

    Thanks again Don!

    Tony
    Last edited by EuropeanAM; 11-02-2019 at 05:18 PM. Reason: Announcements- Please read.

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    #4
    Update:

    Pressurized to 90 PSI and I thought I heard an ever so slight leak at the fuel pressure regulator.

    Next I pulled the port rail, powered the key on, fuel pouring out #6 at the bottom of the rail.
    This I find strange, because #6 plug looks great.
    I do know however that #4 isn't firing right.

    I considered swapping injector #6 and #4 to see if the leak moved, but I had a feeling it's all the result of the failed diaphragm.

    After the fuel leak I decided not to put it back together for the compression test. (
    It was all good last time I tested, and within 2~3# across all 6.
    )
    However... I'm still going to pull all the injectors air & fuel and send them off this week. Considering come January it'll be 8 years of service, 287 hours, the injector service is a wee bit past due.


    With the above thought in mind, I pulled the fuel pressure regulator diaphragm today.
    BINGO!
    Has a tear in it a good ¾" long where you can see the inner fabric on one side. The other side it looks totally perfect.

    Wasn't gunked up at all. In fact, there was a little tiny bead of gunk under the inner spring cap about the size of the head of a pin. Other than that, everything is totally clean. Basically the same thing as when I pulled the VST off last year to clean it out when replacing the fuel lines.

    That now begs the question of which diaphragm do I need, being as there are two.
    10 PSI Part# 8M6002990
    OR
    15 PSI Part# 8M6002989
    Last edited by Dixie Chicken; 11-03-2019 at 05:21 PM.
    Later,

    Dixie Chicken

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    #5
    Will you post a picture of the diaphragm just for our knowledge?
    Chad Snow / Massachusetts
    2007 Ranger Reata 210 - Mercury Optimax 225 (#1B446134) - 12' Talons
    Carbon12’s @ Bow w/ AT- live 12 w/ 3D & live 7 @ Helm


  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #6
    NEITHER. You don't need a regulator- you need a DIAPHRAGM. 8M6002988 is the part number.

    Important Note: Pressures must be confirmed with DEAD-ON accurate instrumentation (recommended method is a high-speed USB Transducer with digital readout) after reassembly. If pressures are not at specification, the regulator must be calibrated.


    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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    #7
    Quote Originally Posted by EuropeanAM View Post
    NEITHER. You don't need a regulator- you need a DIAPHRAGM. 8M6002988 is the part number.

    Important Note: Pressures must be confirmed with DEAD-ON accurate instrumentation (recommended method is a high-speed USB Transducer with digital readout) after reassembly. If pressures are not at specification, the regulator must be calibrated.

    Got it.

    After reassembly next week, if the pressures are within range with the Mercury gauges, is that close enough?
    *Considering before all this, I had a 20psi difference between fuel and air side.*
    Later,

    Dixie Chicken

  8. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #8
    I can't comment on the accuracy of your gauges... it is critical to have something that is DEAD-ON accurate.


    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

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    #9
    Quote Originally Posted by EuropeanAM View Post
    I can't comment on the accuracy of your gauges... it is critical to have something that is DEAD-ON accurate.
    I can say that I reversed the gauges (they are brand new Mercury gauges) to see if one was reading high, and had the same readings (as the initial test).

    Hopefully it'll be back together by the middle of next week. Chris is doing the injectors.
    Forgot to mention I did pin out the injectors with an ohm meter. They are all exactly where they should be, so there's SOME good news.


    Once back together I'll check the things I didn't get to before.
    1: Vacuum on the pulse pump.
    2: Pressure at the VST, as well as at the fuel rail. *Via the glycerin filled Mercury gauges.*
    3: Compression testing (both cold and hot)
    *Was interesting to read the different ways to check compression in the other thread here.*

    I'll know as soon as I crank it if it's cured or not though. There is always that fear that a reed is chipped where I cannot see it via the video with the borescope. Again, only 287 hours so I'm thinking they're OK.

    Just to satisfy my internal OCD'ness looks like I'll have to track down a Mercury tech in these parts that happens to have a
    high-speed USB Transducer with digital readout
    to check the fuel pressure once it's back together. Closest one that has any type of decent rep amongst the local trail guys is out at Oconee, 95 minutes away.

    There is ALWAYS enough time to do it right the first time. Rather than skimp, do it halfway, THEN do it OVER.
    (Tell my 26 year old son that one and get him to believe it!)
    Later,

    Dixie Chicken

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    #10
    Quote Originally Posted by Snowedin3 View Post
    Will you post a picture of the diaphragm just for our knowledge?
    Here ya' go.

    It is critical however to look at BOTH sides. The other side looked like nothing was wrong.



    Later,

    Dixie Chicken

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    #11
    No picture.



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    #12
    Quote Originally Posted by Savage View Post
    No picture.
    Well that's weird.

    I use Microsoft Edge browser and 2 show up there.

    Just opened the page with Internet Explorer, and nothing shows. Hmmmm
    Later,

    Dixie Chicken

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    #13
    Lets try it again, another way. This is a direct upload (rather than from the Album here on BBC).


    Fuel D - 1.jpg


    Fuel D 2.jpg

    WOW so this is weird.
    In Microsoft Edge I can see photos in both posts. This post they are small, have to click to enlarge them.

    Then I loaded the link in Internet Explorer and I get no photos. BUT..... I do get the text for the link(s) at least.
    Last edited by Dixie Chicken; 11-08-2019 at 06:56 PM.
    Later,

    Dixie Chicken

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    #14
    Diaphragm appears to have a bad crimp on it. The washer under the crimp looks cocked.



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    #15
    Quote Originally Posted by Savage View Post
    Diaphragm appears to have a bad crimp on it. The washer under the crimp looks cocked.
    Are you talking about the center section? The little flat 'button' that's tilted?

    That part pivots. It's a ball-in-socket configuration. I'd say over ¼" diameter ball with a machined flat side. It can easily pivot 45° in any direction.

    Don't know how that actually makes it work any better than if it were just flat (non-pivoting) though. That part (as I'm sure you know) faces the inside of the fuel rail, against the insert/nozzle piece that is mounted in the rail itself. I'm thinking it's designed that way so that the center will remain flat against the nozzle no matter how the rest of the surface area twists and/or deflects in/out up/down under load. Just doesn't seem like the unit as a whole would have enough deflection in it to need a pivoting center section.

    Yet that part has a LOT of ability to pivot! You could put that center section against a flat surface, take a pencil eraser for instance, holding it straight up, with the flat part pressed against the flat part of the eraser and no matter how you twisted or pivot the rest of the unit, that center section would remain flat against the flat top of the eraser. (Which when mounted rides against the fuel nozzle inside the fuel rail.)

    When I first pulled the cover and spring I would have sworn nothing was wrong with the diaphragm. The spring side has a large button that the spring fits over that's a good 5/8" across. No matter how hard you look, twist or turn the rubber on that side, it doesn't have any defects. Of course that side is AWAY from the fuel. Lesson learned is that the regulator covers have a 'weep' hole in them. If I'd known what I was looking for, I'd realized fuel was weeping from the hole. It had begun to ever so slightly discolor the metal from the small amount of fuel that was weeping, then drying without remaining wet all the time. Inside the cover though you could see where fuel had been sitting on the inside bottom of the (metal) cover.

    This problem is new, and didn't show up till the last couple times on the water. But... my wife first noticed it was a bit harder to start and had a rough idle. *She's the one that cranks it off the trailer, warms it up, and pulls back to the dock while I park the truck/trailer.* There was also a new fuel smell, (besides the tank vent). NOW I know to look for the telltale sign of 'weepage' on the regulator covers (on BOTH fuel rails). ;-)
    Later,

    Dixie Chicken

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    #16
    Update:

    First, thanks to Don for the input here. Also, thanks to Chris Carson for the amazingly quick turnaround on the injectors! Shipped them to him last week, he had them back to me Monday.

    Wanted to put them back in Monday as well, but my low back has had other plans the last couple months. WAAAAAAY different plans than I keep in my head. Fighting the pain I got it all back together Tuesday. One word.... SCHWEET!

    I suggest that anyone running an Opti, (or any 2-stroke for that matter) that has a couple hundred hours on it, GET - THE - INJECTORS - SERVICED! Not when you get around to it, not when it starts running weird, but NOW! The difference in throttle response isn't something I can describe well enough here, but trust me, it IS worth the effort. I know from diagnosing my problem that the injectors were not the main cause. As Christ told me the fuel injectors were pretty good, but the air injectors were off a bit. That said, #4 was fouling the plug bad, and #2 was starting to get right behind it. All this was because of a failed fuel pressure regulator diaphragm.

    Yesterday was a beautiful day here, the wife took off, and we headed to the lake!
    (Much to the detriment of my back, which has me back to reaching for a walker to get around the house today.)

    From the moment I bumped the starter in the driveway it was noticeably smoother. Once on the water it was crisper, and had better throttle response than I think it's had since I've owned it. WOW at the difference! Let me restate... that's not turn the starter switch and have it turn over a few times before it starts. That's BUMP it and it fires to life.
    Wow, just WOW!

    One thing I still need to do PROPERLY is get compression readings. Did it Tuesday after everything was back together, but not with the throttle body WOT, and not at full operating temp. My only attempt there was to see the *balance* between the cylinders, and/or to see if there a problem with a given cylinder. That 'down and dirty' test showed all were literally identical, maybe 1 PSI between them. So far, so good.

    Do still have an issue that I'll need to address as soon as I can MOVE again. Earlier in the thread I noted that my pressure differentials were wider than they should be. I know they've been off on this motor since new, because nobody has ever been into it and it's ran fine until the diaphragm failure.

    Current readings, air is solid at 94 PSI, and fuel is still a good 18~19 PSI higher (Mercury glycerin filled gauges). Reverse gauge connections, same readings. Next week I'll try to (if my back will let me) drill out and remove the freeze plug thingy on the fuel pressure regulator to see if the adjustment screw can actually be turned. According to the shop manual it may be locked in place, likely with red Loctite. If it is locked where I cannot turn it... I'll order the replacement kit.

    If the screw can be adjusted I'll lower the differential closer to factory specification. I do realize this is a CRITICAL adjustment, no going nuts and turning full turns in any direction. Very VERY slight adjustments and watch the gauge CLOSELY. That's providing it'll adjust at all.

    I also TOTALLY INTEND on having it set with a High Speed USB Pressure Transducer. Working today on finding a tech that has one that I can get with between now and Christmas.


    Don, to clarify... that part number for the 15 PSI Regulator Kit is 8M6002989..... correct?

    Again, thanks to everyone here for the help thus far. I ended up spending quite a bit for specialized gauges and tools to replace a $185 diaphragm. LOL From a color borescope that records videos, air/fuel gauges, vacuum/low pressure gauge, compression gauge, as well as the Mercury tool for removing/installing the diaphragms and a few other small specialized Mercury tools for the fuel system etc. but standing and working on a clean outboard is almost TOO easy and way too much fun compared to being bent over in a dirty greasy engine bay. FUN TIMES INDEED.
    Later,

    Dixie Chicken

  17. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #17
    When you get down to the pressures, give me a call. DON'T start buying parts or regulator kits, because you likely do NOT need them.


    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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    #18
    Quote Originally Posted by EuropeanAM View Post
    When you get down to the pressures, give me a call. DON'T start buying parts or regulator kits, because you likely do NOT need them.

    Thanks Don, will do.


    I'll try and tap out the cover on the fuel regulator next week and see if the screw will turn. I'll lyk how that works out.

    Thanks again!

    Tony

  19. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #19
    Give me a call before you attempt to turn the screw.


    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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    #20
    Quote Originally Posted by EuropeanAM View Post
    Give me a call before you attempt to turn the screw.
    Don, would it help if I just removed the whole thing and soaked it in some sort of solvent first?
    *Remember I have the Mercury tool*

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