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06 f225 TXR

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  • 06 f225 TXR

    Tried to post this earlier but it didn't go for some reason so I'll try again.

    I think I've got a fuel issue but I'm getting stumped at this point. I can't run any more than 3/4 throttle. Push past and it bogs down and looses RPM. 4K RPM is all I can get until it starts to come up on plane then it will slowly gain speed and RPM up to about 5200 then that's it when it's loaded. When it's only me I can get to WOT but I have to slowly put the hammer down not just slam it. I've replaced the spin on filter, the small cartridge filter inside the hood, the u shaped filter on top of the VST tank, and the VST filter on the bottom of the high pressure pump. I ran it in the lake without the hood on it and the filter under the intake plenum never loses fuel or level in any situations. I've checked both of the little aluminum check valves and they work like they should. I even blew air all the way through the canister system and out through the hole in the hood latch. The orifice/ air vent was stopped up but I took it apart and got it working. After re-installing it and doing a lake test it seemed almost fixed on the first run from the trailer when it was cold but still had a slight hesitation that you can hear in this video: https://www.youtube.com/watch?v=IZF8QvF_mvg . After running it for 15 minutes or so this is what I was getting: https://www.youtube.com/watch?v=aeCz6thvkl4 . This video is of the GPS unit where you can see the RPM of the motor better: https://www.youtube.com/watch?v=HXV6m6MeAzA .

    I have replaced the every filter on the system and checked all the lines and components under the hood, and it all seems to check out. It ran much better yesterday than it did on Monday, after I repaired the orifice, but it's still not right. It was only me in the boat for the test so I know when I load the boat I'll be back in the same creek. I got to thinking yesterday that during the off season I added the command link cable to my engine and it was a couple months before I used the boat. I don't remember when my trouble started though, I guess it's possible that I have the line pinched in the rigging tube and it's been slowly getting worse over time. I pulled it out and replaced and still have the same issue, runs good until it warms up then runs terribly. I don't know what it could be and I don't want to keep throwing parts at a problem. Up to this point everything I've done could be justified as maintenance.

  • #2
    How many hours ? I would start basic with a compression test to see if the motor is healthy. Check the plugs to see if they all look normal. Also test the pressure at the vst when running especially when the problem occurs. Could be clogged injectors. Spark plugs will tell you a lot..

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    • #3
      at the top of the port side fuel rail is a Schrader valve;
      connect a gauge and monitor the pressure
      if it does not drop when the engine 'bogs'
      then its the injectors
      or its not a 'fuel' problem

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      • #4
        Motor only has about 500 hours on it. From reading posts on this site I figured rail pressure was going to be a question so I bought a gauge from Harbor Freight yesterday. Hopefully it has the fitting I need, but I'll be trying it this afternoon. I didn't think about a compression problem since it runs so smoothly and strong in the other ranges. I did forget to mention that sometimes it does cough and almost backfire if I leave the throttle pinned, instead of backing off to 3/4.

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        • #5
          I forgot to ask what pressure should I be getting at idle and under load?

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          • #6
            at 'key on' before starting then engine,
            the HP runs for a few seconds - you should expect ~44 psi
            that's the max
            once it starts and idles, manifold vacuum drops it to ~38 psi
            the more the throttle opens/lower manifold vacuum,
            the closer it returns to 44

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            • #7
              Tested today:

              - Compression 150-160 on all cylinders
              - Found one plug with a cracked ceramic so all were replaced

              Rail pressure checks (tested in the lake):

              - Key on pressure 44 psi
              - Idle pressure 38 psi
              -5/8 throttle pressure 42-44 psi
              -anything past 5/8 throttle pressure drops to 28 psi

              I never lose the level of fuel in the bowl under the intake plenum so I don't think it's a supply issue. Going to put an external tank in the boat tomorrow and recheck to rule out supply though. The issue is intermittent though. I had a buddy with me today. From cold it ran decent though still seems weak. Once it got to temp it had a new symptom, from stopped I went WOT, RPM peaked at 4200 then started surging back and forth from 4200 to 4400 or 4500 (it used to cough and backfire at this point not surge). The more we ran and tested it quit surging and seemed to start running a little better but still not right. After 20 minutes of running I dropped my buddy at the beach to get the truck and while he was out I ran it again and it did worse than it did all day. 3800 was all it would do at WOT, I backed off a little and got it up to 4300 but that's all. Frustrated at this point I just put it on the trailer.

              So what I know for sure now is that I'm losing rail pressure for some reason. Bad pump or bad connections?

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              • #8
                Originally posted by OneStepSally View Post
                -5/8 throttle pressure 42-44 psi
                -anything past 5/8 throttle pressure drops to 28 psi
                excellent -
                in the sense that it absolutely is a fuel supply problem,
                and not the injectors

                seems you've already addressed
                many of 'the usual suspects':

                Originally posted by OneStepSally View Post
                replaced the spin on filter, the small cartridge filter inside the hood, the u shaped filter on top of the VST tank, and the VST filter on the bottom of the high pressure pump...checked both of the little aluminum check valves and they work like they should
                unfortunately,
                the opportunity was missed to use the primer bulb,
                to determine whether or not the problem was in the VST,
                or a failure - or inability - to keep the VST supplied

                given what you've already replaced,
                that seems to leave a restriction,
                or an air leak,
                between the boat tank and the LP pump

                A restriction between the boat tank, and the primer bulb,
                would cause the bulb to be 'sucked flat"

                if that isn't happening,
                the restriction could only be between the bulb and the LP pump
                (pinched hose, blocked hose)

                an air leak in could be just about anywhere -
                split hose, loose hose connection, filter bowl loose;
                patching in a short length of clear hose near the engine
                can help to visualize air bubbles and confirm a leak

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                • #9
                  Just as an FYI, I once discovered the inside layer of a Mercury fuel line (from my bulb to the under the hood, factory fuel filter) CAME APART!''

                  Looked like thin spaghetti. Caught it before it did any damage but certainly something to be aware of...
                  Scott
                  1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR

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                  • #10
                    Ran it today on an external tank today and it definitely seems to be a supply issue. It ran great on the external so I swapped it back to the on-board system and it ran great. I ran it for about 10 minutes and it started running bad again. I switched it back to the external and was fixed almost immediately. I will be changing out hoses and trying again. It just seems odd to me that I never see a drop in the level of the fuel in the clear bowl. I wasn't able to check pressures today cause I didn't have anyone with me, but I will have help next time out and I will check them. I will report back after the changes. I will be adding a ball too.

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                    • #11
                      New update. I've now replaced the lines all the way to the tank. I blew air through the line after I replaced and everything checks out. Only place air was going was out the tank vent line. Lake test and it is just as bad as it ever was and when I went to load it wouldn't go above 2200 rpm. I added the ball back in the system and there is no change to the engine at all when I squeeze it. It is slightly soft but after 3 or 4 pumps it gets hard. Video of today's run here: https://youtu.be/-yLw3YMmi9M

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                      • #12
                        Key on pressure 44 psi
                        - Idle pressure 38 psi
                        -5/8 throttle pressure 42-44 psi
                        -anything past 5/8 throttle pressure drops to 28 psi
                        This was from number 7 the pressure dropped to 28 wouldn't you think high pressure pump

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                        • #13
                          I was leaning that direction but needed to rule out supply from the tank. See post #10, it seemed to be better when I ran it on the external tank but now I'm at a loss. Maybe it is a weak LP pump and it having trouble pulling fuel through the 15 ft of fuel line under the deck?? I need more guidance from professionals! Where should I look next or what should I try?

                          Also there was a new symptom today that I thought I noticed the other day but I wasn't sure. On the first run from cold it took off and went up to about 48-49k rpm and then started surging. It would fall to 46k then surge to almost 5k and at about a 2 second cycle. It only did this with the throttle position at WOT, back off a little and it would smooth out. Only to start the same thing when pushed back down. After a couple minutes I stopped and pulled the lid to get to the ball and took back off with no surge. I hadn't squeezed it yet so I don't think that was the cure.
                          Last edited by OneStepSally; 07-11-2020, 04:54 PM.

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                          • #14
                            If the VST is running low on fuel at high RPMs, the HP pump cannot pump so the pressure drops.
                            hook the other tank back up and see if that still helps.

                            either there is a restriction or air is getting into the line
                            Last edited by 99yam40; 07-11-2020, 05:12 PM.

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                            • #15
                              Wouldn't pumping the ball force fuel into the vst? I can pump it a few times and it gets really hard but the engine does not react at all.

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