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BigSix

How to Jump "Low Oil Shutdown Switch"--for test

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BigSix
All: In another post, I dicussed carb problems. I may still have a carb problem, but I would like to eliminate (as a test) the “Low Oil Shutdown” system on this 1994 5 hp. B&S “Industrial Plus” engine. This is the one on the Northern Tool “Trencher” (a towable minibackhoe) I wrote about yesterday. The thing is, the carb was severly gunked, but I cleaned it all, (explained below) and the engine runs exactly like it’s fuel starved—runs for 2 seconds if you prime it through the plug hole—then dies. However, because I’ve been all through the carb and all the passages are clear, and it’s a gravity feed tank, that’s feeding, I’m wondering if that Low Oil Shutdown could be the problem? I guess the question is, how does it function? If it cuts spark instantly, and continously, I can forget about it, as I've got spark. However, if it waits a couple seconds to sense the level, upon startup, then cuts it, then that could explain my problem. The warning light is not lighting or flickering, as the on-line manula says it would, were low oil the problem. However, the machine’s been outside, tarped, for years, with obvious moisture (corrosion) around engine, and had a mouse living in it. I’m just wondering of, by it’s very nature, the low oil shutdown would be designed to wait, letting the engine run a couple of seconds, then sense low oil (my theory would make sense if it were a pressurized oil system, but it’s not…). Anyhow, there’s three wires off the switch, and I was wondering if anybody knew how to jump the switch, to eliminate it from the possible cause of this problem? (Admittedly it does seem like simple fuel starvation, in that, after a prime, it fires right up again). Oil is up to full, but machine is tipped 25 degrees. Hmmmm.... I will add more oil tomorrow. Also, there is a wire off of the low oil light/on/off switch (one of three wires) yet an inline connection near the engine has is obviously homemade. And this wire is not connected to anything--it simply wraps up around the hydraulic controls, and the insulation is pealed near the end, making me think it is a home made kill switch, but I'm not sure. The connector near the engine is definitely not stock. Re: the carb cleaning (no carb kits available on Sunday), I took the carb off last night, as it was way gummed up-float glued in place. A mouse ran out from under the shroud after I'd been at it a few minutes. Took carb home, tanked the carb, ran wires through all openings, including two tiny ones (1/64th? 128th?) and they're clear--spray cleaner flows through everything. Blew it out, salvaged the gaskets, everything looked good. Pulled shroud, cleared mouse nests, Pulled 10 times, nada. Primed, and on second pull, rope broke! (Mice). Took off recoil, used scraps of twine to pull start it off the flywheel. Twine kept breaking. Priming is a pain--plug accessed through gas tank, in a well w/ a rubber cap. (HemiTrencher?) Engine fires, runs 'till prime gone (2 sec.), then nothing. Did that 10-15 times. Dropped float bowl--gas gushes freely. All of inside of carb was cleaned, so I knew it would flow. I plan to reexamine the tiny, clean carb again. There is no fuel pump diaphram, as it is a gravity feed tank. When the engine runs, it sounds excellent--and very quiet! The airfilter (paper element, with foam "dirt guard") is barely dirty, making me think the machine has hardly been used. So, what part of the carb did I miss? Or, how can I jump the Low Oil Guard switch, just to make sure I goofed with the carb? Thanks.

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PatRarick
The low oil shutdown is nothing more that a float operated kill switch. When the oil level drops to a certain point, the float drops to a point where it activates the kill switch. You simply disconnect it to over ride. The light won't flash unless the oil level is too low, or if the ignition switch is in the off position. Since it fires and runs when primed, I would assume that it's a carb problem. Sounds like there's still some gunk in the main jet. Try to start it again, and as it begins to die, give it a short burst of carb cleaner into the carb throat. If it catches again, you'll know for sure that it's a carb problem. Remove the carb bowl. Put the nozzle tube of the carb cleaner up into the main jet. When you spray the cleaner, it should go right into the carb throat. Pat

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sandyhillbill
had this same problem with a 10 hp briggs on a 5k generator last year. the generator is not used much and it sat in my shop without being used for several months and when the occasion arose to use it the carb was varnished so bad I never could clean it. Ended up buying new carb and now I put a product called STABIL in all my machines that are not used on a regular basis. I also try to start the generator at least once a month to be on the safe side. hope this helps.

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arnoldir
Sounds like a carb flapper, or "carbuncle" as we called them in the motorcycle shop. As the gas in the carb evaporates off it can leave a thin membrane of gunk in the main jet. If you just blow it out, the gunk will "flap" over sideways and a quick check will show a clean hole. Soon as it's full of gas the flap "flops" and chokes off the fuel. I've had this happen to me, only way to be shure it's clean is to hold it up to a flashlight and inspect the entire inner surface, or put a pipe cleaner up through it. I would not have believed it if I had not seen it with my own eyes, i ended up loosing a bet with my boss and worked for free that day.

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BigSix
Alright you guys. That's all good info--thanks. Pat: I especially appreciate knowing how the Low Oil Shutdown works. The loose wire was freakin' me, but now I know I can eliminate that as a possible cause of this problem. One thing: My red, translucent "On/Off" switch never lights up, even if you pull the engine with it off. From what you wrote, I take it it should, perhaps as a test to show the light works? That would be consistent with how "idiot" lights in cars work. Just wondered if I needed a new switch, (or bulb?) in future. Sandy: Stabil is definitely that way to go. UCD: I hear you, but with a gravity feed carb., I wouldn't think a bad float bowl gasket would affect fuel delivery. It's not leaking gas, but I guess that doesn't rule out a vacuum leak on the high side of the bowl gasket.... Arnoldir: No kidding! You know two of the passages are like 1/64th, or even 128th of an inch, in dia., and I ran fine wires through them, gently, and then blew carb cleaner through all of them, both directions. It does spray into the throat, from the main jet. I will examine the mainjet for more than three holes (on in center, two on sides) but they are all clear. The "carbuncle" theory is starting to sound better--very glad to learn of that--thanks!

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PatRarick
There should be three wires on the lighted ignition switch. One goes to the coil to ground the ignition for shutdown. One goes to the low oil shutdown, and one to the ground. The ignition primary circuit powers the light and the "Oil Guard" grounds the other side of the bulb. I may be mistaken on the light flashing if the switch is off. I'm working from memory here. In any case, if the ground wire is disconnected, the ignition switch is rendered useless. You will have spark with no way to shut it down without grounding that wire, or if the oil level is low. If the wire from the Oil Guard is disconnected, the low oil shutdown will not work but the engine can be killed by grounding that wire. The light will flash when that wire is grounded, regardless of oil level. If the wire between the switch and the coil is disconnected, you can only kill the engine by choking it, removing the spark plug wire, or grounding the spark plug. You say that the engine is at about a 25 degree angle. There has been a lot of problems with "Oil Guard" here. These engines are mounted on agricultural field sprayers. When the engine oil gets warm and thin, operating at an angle or simply the bouncing of the unit will cause the ignition to cut out intermitantly. I will make the assumption that this was a problem with the trencher. The owner disconnected the Oil Guard wire to keep the engine from cutting out (or stopping completely if the operating angle was sufficient), and used it as you say, a remote shut down. Pat

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D-17_Dave
You metioned earlier it had a 5.5 briggs engine, right? As I remember the nozzel( the part in which the gas travels up towards the carb neck) isn't the main jet. The jet may be located in the bowl nut by means of a tiny orrifice to act as the metering device. Pull the bowl bolt back off and clean this with the wire of a wire brush then spray some carb cleaner through it. You should be able to blow through it if it's clean. Try it then. Ran into the same thing yesturday on the neighbors tiller.

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BigSix
Pat: Thank you for the additional detail on the "Oil Guard" system. I am encouraged to hear of the difficulties with the sprayers. Actually, I got thinking about this after your last post. As I say, the oil is low, in that it reads "full" when tipped 25 degrees. I think you're right that it could be the "Oil Guard" because one would think that once the rpms start to build, the oil in the "splash" lube system will be bounced around/up the sides of the case, thereby lowering the oil level and triggering the low oil shutdown. I'm gonna go back through the carb, since I have it off, but before I add oil, I'll just try the carb again. If no joy, and then if after adding oil, it works, well, then I learned something. Thanks. Oh. Btw, I checked the spark the last time I was there--it does go off, if you turn the switch off, and spin the engine. So somehow, it's functioning even with one wire off. Perhaps this is an earlier model, or modified in some way. Once I get it home, I'll take a pic w/ my borrowed camera, and show you. Maybe it will prove interesting. D-17 Dave: I hear you. It does have that main jet which is the nut that holds the float bowl up. It's got three holes, and they're all clear, but I will rexamine for more holes, or arnoldair's "carbuncle" theory. Re: the cleaning I did, as I say, even the two miniscule (128th inch?) holes in the carb throat, right near the throttle butterfly, are clear and flow carb cleaner through them.

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