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O.T. - Fuel Shutoff and Vacuum Fuel Pump

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  • O.T. - Fuel Shutoff and Vacuum Fuel Pump

    I have a new IKON zero turn mower with a Kawasaki FR691v. It apparently uses a vacuum fuel pump.
    I like having a fuel shutoff on most of my stuff, and at the end of the season, I will run the carb dry (although I never have an actual problem either way).

    So, my question is - will shutting off the fuel and running the motor until it dies stress/reduce the life of this vacuum fuel pump in any way, and would there be any preference as far as placing the shut off valve before or after the pump itself? Locating it to ease filter changing is a non-issue. A small point perhaps, but I thought I would see what you guys have to say.
    Location: North Central Texas

  • #2
    No problem either way. The pump's diaphragm is restricted and limited in travel so it is never stressed. The biggest killer is ethanol. I've replaced two already in the neighborhood this spring. The diaphragms get hard and brittle and come out of winter's hibernation looking like a slice of Swiss cheese.

    Some outdoor power equipment which utilize vacuum fuel pumps that get their vacuum signal from crankcase pulsations actually have a fuel shutoff petcock at the tank, especially those that will gravity feed to some degree. Always a good safeguard in the event that a float should stick in the slightly open position after shut down.

    Having the fuel shutoff after the pump works good too, although often times not as convenient to access, much like the float bowl drain. The pump simply deadheads at the shutoff instead of at the needle and seat in the float bowl.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories​

    Location: British Columbia

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    • #3
      Yep, mirrors my experiences. Ethanol gasoline sucks.

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      • #4
        Thank you for quality confirmation from a trusted source.

        Let's digress.
        The ethanol thing continues to give me pause. I have a lot of small engines of varying ages and, for a lengthy period, was responsible for a LOT of engines at my fire department. The oldest in my fleet, I think, is a McCulloch weed eater that is over 30 years old, and aside from 2 or 3 primer bulbs and one fuel line change, has never been touched nor has the carb ever been opened (it will hurt when that one eventually dies).

        I always use the standard 10% ethanol fuel. In all these many years, I have had very few fuel related issues in total, and none that i could attribute to ethanol.
        This appears to be an uncommon experience, so why would that be?
        The only things that I perhaps do differently - 1) everything gets super unleaded, and 2) I add 2 ounces of Stabil Storage per 5 gallons, at every single filling.

        Is the addition of Stabil the magic? IDK, but my results have been categorical, and with a large and diverse sampling size. and over a long period of time.
        AND, why would (my) ancient motors seem to be OK with ethanol, and new motors, DESIGNED to utilize it, seemingly having widespread and continuous problems?

        Location: North Central Texas

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        • #5
          It's not exactly solely the ethanol itself that's the problem. Some of the problems don't occur on engines that get regular and frequent use, because the gas gets used up, and any absorbed water along with it. The big problems come when the gas sits in the bowl for a season or two, or more. Ethanol absorbs water from the air, and leaves it sitting in the tank and the float bowl. Many carb parts these days are aluminum, and aluminum and water do not mix. The water causes the aluminum to oxidize (white crystals/powder grows on the aluminum). This generally locks any moving parts up solid. The ethanol also does harden rubber parts that need to be flexible for the carb to work. Whether that's seals or fuel pump diaphragms or vacuum diaphragms. 20-30 years ago before ethanol gas I would have engines sitting for years and years and they'd start right up with no issues. Since ethanol's introduction into gasoline I've had to tear apart so many more carburetors it's not even funny. And I have done it for many more than just my own engines.

          Location may have something to do with it as well - in terms of temperatures. Areas that get below freezing and thaw back out multiple times a season probably introduce even more water into the equation through condensation. Areas with more stable warmer temperatures don't have that problem.
          Last edited by eKretz; 05-19-2021, 01:04 AM.

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          • #6

            If I remember right, you're in NE Texas so it could be the particular formulation in your locale that's responsible-

            https://www.api.org/-/media/Files/Po...ements-Map.pdf

            I have a customer at work that's a formulation engineer, he said it's not the Ethanol that's the issue with eating the soft parts in a fuel system, it's the other additives like Toluene and Benzene and a few others that are the culprits there. The damage Ethanol is responsible for is corrosion of zinc plated steels and zinc alloy components.

            I just need one more tool,just one!

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            • #7
              A bit north of DFW Darin. So, the southern blends of fuel don't attack the diaphragms like northern blends?
              So, do you northerners have more of a problem than those of us in the south? Shouldn't snow machines and snow blowers have proportionally more troubles due to their use being specifically during cold weather, when the blends might be most problematic?
              Location: North Central Texas

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              • #8
                I don't think that's completely the case ( hardening solely due to winter/cold weather gasoline formulations). I have been through a large number of summer-use-only carbs (jetskis) with the same hardened diaphragm problems. Those would almost certainly never have had winter formulation fuel put in their tanks.

                I have had the problems in mowers, weed trimmers, snowblowers, dirtbikes, jetskis, chainsaws, etc. Never had the problem in a fuel injected gasoline engine, and never in a diesel.
                Last edited by eKretz; 05-19-2021, 02:14 AM.

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                • #9
                  Originally posted by Joel View Post
                  A bit north of DFW Darin. So, the southern blends of fuel don't attack the diaphragms like northern blends?
                  So, do you northerners have more of a problem than those of us in the south? Shouldn't snow machines and snow blowers have proportionally more troubles due to their use being specifically during cold weather, when the blends might be most problematic?
                  What's a snowblower?đŸ˜‰ I'm further south than you, but far enough east to be in a conventional blend area. It's not an easy problem to put a finger on, some engines have trouble and some don't. I mostly don't have trouble with mine, but then again I don't buy gas with Ethanol in it if I have the choice. I remember gas back in the day didn't have these issues, the only trouble back then was it lacquering up in the tank.

                  Here's a handy map if you want to find ethanol free gas in your state-
                  https://www.pure-gas.org/extensions/...p?statecode=TX
                  I just need one more tool,just one!

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                  • #10
                    Some very good observations mentioned on the issues associated with the use of oxygenated fuels, they pretty well echo my experiences as well.

                    Geographic variables, weather etc. and the fact that all fuels from various sources although meeting a standard, are not the same also play a role.I believe that variables in the supply and distribution chain of the elastomers used can also be a contributing factor.

                    Although the auto industry has been very responsive in meeting the challenges with the use of ethanol fuel blends, they also do not as a rule have to deal with the seasonal use of their products. This and the fact that they do not have to contend with a fuel system that is vented to the atmosphere as freely as those on lawn and garden power equipment is also another key to this random puzzle. Even the finest fuels available will cause major problems if left in a carburetor too long since the float bowl is freely vented to the atmosphere. Diaphragm or "pumper" type carbs on two cycle engines are a bit better able to handle this aspect since they are mostly a sealed system.

                    I see that while small engine manufactures and those from the marine industry are now begrudgingly approving the use of 10% ethanol blends they are gagging at the thought of having to deal with 15% blends. I think this speaks volumes about the issue being a real one.

                    I realize the problem is not a blanket one that is all inclusive, it is however a real enough threat to not be ignored.
                    Much as in smoking cigarettes, even though I know of those that have smoked a pack and a half of cigarettes till they hit a hundred, it's still not a habit I would endorse.
                    Home, down in the valley behind the Red Angus
                    Bad Decisions Make Good Stories​

                    Location: British Columbia

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                    • #11
                      At work, we recommend both Sta-Bil and Startron fuel additives for ethanol mix fuel. Our customers who use these products don't have fuel system issues. We're talking commercial air cooled carbureted engines that would be to expensive to fuel with ethanol-free premium gas.

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                      • #12
                        Originally posted by CarlByrns View Post
                        At work, we recommend both Sta-Bil and Startron fuel additives for ethanol mix fuel. Our customers who use these products don't have fuel system issues. We're talking commercial air cooled carbureted engines that would be to expensive to fuel with ethanol-free premium gas.
                        I bought a new Husqvarna mower a few years back and the owner's manual says the warranty will be voided if you don't use an additive to combat the effects of Ethanol at *every* fill up. The only Sta-Bil product on the shelves by me is advertised as "complete protection" or something like that and can be used for storage and as an Ethanol treatment. Now I don't even need to think about cleaning out the floats on my old snow blower. Everything runs with the Sta-Bil stuff in it and it always fires right up, even after being in storage for half the year. Seems to work...
                        Last edited by Fasttrack; 05-19-2021, 02:30 PM.

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                        • #13
                          Originally posted by CarlByrns View Post
                          At work, we recommend both Sta-Bil and Startron fuel additives for ethanol mix fuel. Our customers who use these products don't have fuel system issues. We're talking commercial air cooled carbureted engines that would be to expensive to fuel with ethanol-free premium gas.
                          Yes the Sta-Bil is good alternative, not personally familiar with the other product but I'll acknowledge that it too would be a good choice considering the source of the recommendation.

                          These choices are especially important on carburetor equipped engines that see periodic use and are subjected to long term storage. This applies especially to those engines that are stored during the warm weather summer months since this is when most of the aromatic components of the fuel are allowed to evaporate. However cool and damp environments offer their own set of challenges.
                          Home, down in the valley behind the Red Angus
                          Bad Decisions Make Good Stories​

                          Location: British Columbia

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                          • #14
                            Well, the ethanol issue has come up again and again, so it is good to see a credible consensus forming.
                            So - we have 3+ people who have had categorical success (even in a northern climate) by doing nothing other than using Sta-bil 100% of the time.
                            I use 'Sta-bil Storage', which is the red stuff. The only thing it says on the bottle regarding ethanol is "Effective in all gasoline & ethanol blended fuels, including E-10 through E-85". I have always used the minimum recommended amount (2oz/5gal).

                            More data/experience would be good, so keep it coming.
                            Location: North Central Texas

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                            • #15
                              From my new mower manual:

                              Click image for larger version

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                              Location: North Central Texas

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