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I just picked up a Troy Bilt Bronco with a twin cylinder 18.5hp ELS500 engine. Sorry, I don't think I'm going to be able to find the engine code without taking the hood and side panels off.

The guy I bought it from said he had taken it to a local service center, one that I know to be reputable, for a fuel issue. He showed me where they installed a fuel cutoff valve between the tank and engine. He said you have to keep the valvle closed when it is not running or fuel will run into the crankcase. He said they told them is was some kind of valve issue.

Can someone please tell me what problem they were attempting to correct so that I can try to fix it properly? Would it have something to do with the fuel pump? I would think it would have to be something fairly costly in parts or labor for them to just install a cutoff switch rather than fix the problem. Any help would be appreciated.

"K&T Parts House Lawn Mower Parts and Chain Saw & Trimmer Parts" You may very well have a carburetor problem, post numbers when you have time as well as engine manufacturer, thanks. Example B&S engine: model xxxxxx, type xxxx, trim xx.

Many two cyl. Mower engines have a fuel cutoff solenoid located at the fuel input to the carburetor. When the ignition key is off, the 12 volt from the battery is cut off to the solenoid and no gas flows into the fuel bowl. When the key is in the crank or run position, the 12 volts is applied to the fuel solenoid and fuel will flow into the carburetors fuel bowl. It prevents engine run on after turning off the key. There are other factors which eliminate the engine to continue running, but I won't cover that at this time.

I have experienced bad solenoids in the past. Testing them is fairly easy and quick. The price of a new solenoid may shock you. An example of a new fuel solenoid on my Scag Turf Tiger is approximately $135.00 retail. The Carburetor is $400.00 Plus.

Your description indicates a attempt to get the mower up and running in a inexpensive manner. :confused2:

Suggest you provide your engine and mower models and serial numbers...You'll get more input from knowledgeable people when it's provided. :thumbsup:

Good luck on your project.


Deamer1

All very good info, thanks! My first thought was a carb issue, I was thinking maybe a bad float or something like that. When he said they told him it was a valve issue I didn't really know what to make of that. I have worked on a JD mower that had the electrical solenoid on the bottom of the carb. When I first ran across one it took a moment to figure out what I was dealing with. I thought I had a bad solenoid on that mower but I had an identical mower and engine and swapped the solenoid and ruled out that problem, that ended up being an issue with the fuel pump. I do remember pricing the solenoid on that engine and yes, I was suprised at how expensive it was. This certainly seems like a very likely candidate for the problem with this mower.

I will do my best to provide the engine numbers tomorrow and I may pull that solenoid off and test it. I picked up this great looking Bronco for $150. I needs a minor deck repair that I should be able to manage with a little welding. Other than that it looks great and runs great. I think it would be worth it to spend the money on the solenoid if that is the problem to make it right. Using the fuel cutoff switch just isn't going to get it.

The valve the guy was talking about is the float needle valve, not the fuel shutoff solenoid. What you need to do is remove the carb and give it a 24 bath and cleaning. Then replace the float needle and seat before reassembling. Should solve the problem he tried to fix with a bandaid (installing an inline shutoff valve).

Yes, that could be, I didn't think of it that way. Apparently they didn't explain it well to the guy I got it from either. He thought they were talking about the intake/exhaust valves. I asked him if it could be an issue with the carb and he said, "No, not the carb, they told me it was the valves." At any rate, that could very well be the issue. I just find that hard to believe, that a reputable service center would not pull the carb and clean it, that's easy stuff, not time consuming at all and the carb rebuild kit is just a few bucks. The guy I got it from ended up buying a $1,400 Husqvarna, had it sitting in his garage, so I doubt he would have told them not to clean it for a few $$ more. I don't know what a pro charges for a carb rebuild but really it's about an hour in labor and $20 in parts. I'm sure they didn't do the fuel cutoff for free, even though they should have, so how much could he have saved?

So if I drop the bowl and lift the float and gas is still running out I'm guessing I've found the problem, correct? If not then I guess I'll continue on to check the solenoid.

If you just drop the bowl, push up the float, and the fuel stops, it does not mean that the needle and seat are good. The needle should seat with 7 pounds of pressure, that's not much, as you can put 10 pounds on with no effort. I recommend clean carb and replace, based on your symptoms. Why it was not done by a reputable firm is puzzling, as depending on the unit it takes 30-45 minutes and the kit costs $5-25. 90% of the people on this forum say go the cheap way, but as I said, it is a bandaid. Here is the procedure we use in our shop and it works 96% of the time, the other 5% the carb needs to be replaced. Not all the carbs are the same, so you may have to tweak it for your situation.

Needle and seat replacement

Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.

I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.

With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. *Next check to make sure that the float does not have any liquid in it. *If it does, replace. *If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.

PS: *On the side of some Tecumseh carbs you will find a plastic cover. *Under this cover will be an idle jet. *Remove it and check to see that the jet is open both horizontally and vertically. *You should be able to push the old float needle wire through the vertical opening.

The float must actually float for the needle valve to be effective.

Okay, so thank you Briggs for putting the engine code on the back side one inch away from the gas tank. With the help of a small mirror I got the engine code, 5B5SX 5012VP, Model 276016.

I went ahead and took the carb off. I've done quite a few carbs now and I follow the same procedure that Senior described. Most of my experience is with older Briggs, Tecumseh, and Robin. These newer Briggs engines are still new to me. The carb was pretty standard and it did have the solenoid. I skipped testing the solenoid because I figured even if the solenoid was bad it shouldn't matter, the fuel shouldn't be getting past the inlet valve if the float is working properly.

I removed the plastic float, it was in good condition. I removed the needle, it was the larger needle with a black tip. There was no red rubber seat in the inlet, no rubber seat at all, just the metal inlet hole. I've seen this on one other carb I've worked on and I dug in there forever and then searched for hours certain that I had just dropped it. I'm guessing there are no rubber seats needed with these black tipped needles. Someone tell me if this is wrong. Trust me though, there is no rubber seat in this one, just metal. If one does belong in there I can't image where it went, unless Ethanol fuel completely dissolved it.

I cleaned it thoroughly and put it back on. It was too late tonight to test anything out. I attached a photo, I left the intake manifold loose where I am pointing in the picture and I turned the fuel cutoff switch on to let the fuel flow. Nothing came out of the loose manifold opening. I'm guessing that if fuel was still running past the float and inlet needle valve it would be running out of that manifold opening, correct? I left it open for a few minutes and then closed the cutoff valve and left it for tonight. Is there a better way to know if the problem is fixed?

If the problem is fixed then I figure I should probably change the oil in case any fuel has run into the crankcase.

I'm wondering how a problem like this would be first discovered. Does the fuel running into the crankcase cause the engine to smoke or run rough? What are the signs in case it happens again. I'm guessing having fuel in the crankcase would be a quick way to seize an engine.

I don't recall ever seeing a seat with rubber ( neoprene). The evolution of needles changed from metal only to neoprene tips probably over 50 years ago. I've read that a correctly working solenoid valve on the carburetor doesn't prevent the flow of gas into the crankcase. I've personally never investigated that but just took the author's word.

You lost me Senior. I know my explanation was pretty confusing. The carbs I am used to working on have the small solid metal (aluminum, I believe) needle and the little black, or red, needle valve seat, or ring. That what I'm used to pushing down or seating with the back end of a drill bit.

The needle on this carb, like one other I have seen, has a black tip. Polymer you say and I suspect that's correct. That's the kind of needle this carb has. When I went to "fish out" the seat, there was no seat, just the metal base inside the hole where the needle fits in.

I was saying that the other carb I worked on with the black tipped needle also had no seat. That led me to believe that these newer black tipped needles are meant to seat directly into the metal opening, with no rubber seat or ring to install into the valve opening.

I'm sure this is a no brainer to you pros, but I'm not used to working on newer engines, or vertical shaft engines either. Most of my experience is with the old Briggs and Tecumseh horizontal engines.

Sorry, just re-read your post, neoprene, not polymer as I said. At any rate, hopefully you got the gist of what I was saying.

I really need some feedback on how I will know if the problem is fixed, could someone tell me if I am on the right track with the manifold opening deal?

I not a pro on small engines and I haven't worked on a newer carb since they started using a rubber seat insert. I suspect the rubber tipped needle was replaced with the rubber seat because of easier manufacturer. I can see no reason for both rubber tip needle and rubber seat.

If were talking about an engine with a rod and piston assembly weighing around 1,200 lbs. then I could visit with you like a pro.:laughing:

LOL, I'm more comfortable with one weighing about a pound! At any rate, I think we agree on the needle and seat issue. Unless someone tells me otherwise I'm assuming there is no seat to fish out of there and replace.

The only issue I have remaining is how I can determine if the problem is fixed. I don't want fuel running into my crankcase and I need to know how to find out if it is. I suppose I could just drain out the oil and leave the drain plug out and then turn the fuel cutoff switch on so fuel is running to the carb and then leave it for a day or two and see if fuel starts to drip out. I'd like to find a more immediate way to testing it though.

arch252 said:

LOL, I'm more comfortable with one weighing about a pound! At any rate, I think we agree on the needle and seat issue. Unless someone tells me otherwise I'm assuming there is no seat to fish out of there and replace.

The only issue I have remaining is how I can determine if the problem is fixed. I don't want fuel running into my crankcase and I need to know how to find out if it is. I suppose I could just drain out the oil and leave the drain plug out and then turn the fuel cutoff switch on so fuel is running to the carb and then leave it for a day or two and see if fuel starts to drip out. I'd like to find a more immediate way to testing it though.

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A more immediate way to check float / needle valve function would be to disconnect the fuel hose from the fuel cut off valve and elevate the end above the carburetor. Using a string and the clove hitch knot ( I did show you how to tie that knot didn't I ) tie it up so it stays elevated. Fill the hose with gasoline until full and stays completely full. This will have filled the carb bowl. If the needle valve is holding as it should the gas level in the hose will stay full all except for a small amount of evaporation over several hours.

Now THAT is experience and we wisdom. That sir, is exactly the reason I get on this forum. I could have stared at that for 6 months straight and I would not have thought of that, makes perfect sense. Thank you very much sir! ☆☆☆☆

I did what Senior described and there is no doubt that fuel is still bypassing the float. Slowly but steadily the fuel level kept dropping in the elevated fuel line. I can't figure out where it's going though. I left the bolts loose and a small gap on the carb to engine intake manifold, the only place where fuel could enter the engine. Fuel never leaked out of the manifold opening. I could see the fuel pooling in the bottom of the air filter housing but that is above the manifold opening level. So if the fuel is pooling in the bottom of the air filter housing where is it going from there? The photo is looking down into the air cleaner housing.

At any rate, I'm going to go ahead and get a carb kit and install a new needle and try it again.

I got a briggs 13.5 hp engine with a number of 28N707 0166 01. When I go looking for information, I find this same engine number on a 15 HP engine. Somebody ain't doin their homework!
Anyway, I got a solenoid mounted underneath the float chamber on my carberator. it has two wires on it. one goes to chassis ground, the other's supposed to go to the ignition switch [on position]
polarity doesn't mean anything here because the solenoid is [above] ground.
When mine failed to operate one day, there was no power [12 volts] from the ignition switch. I installed a single pole switch directly off the battery and to the solenoid coil. Now when I start the mower I just flip up the switch, which opens the solenoid and allows fuel to flow, and further advance the key switch to the "engine start" position. Engine fires right up. release the key switch and it returns to the "on" or "run" position. And go about my business.
When I'm done I put the keyswitch in the "off" position and flip the toggle switch to off. Fuel is shut off to the carb and the engine stops. So whatever fuel is still in the line burns and the engine stops.

Sorry for the delayed response, been on vacation in beautiful Orange Beach, AL.

So...I replaced the needle valve and the metal cup/seat. I did the test again with an elevated fuel line, still seeing the fuel level drop, much slower now. The fuel still does not appear to be going into the engine though, I still don't see it passing in though the intake manifold, just seems to be holding in the bottom of the air filter housing.

At any rate, I reconnected the fuel line and drained the oil out. I left the oil drain plug out and I did not put fresh oil in yet. I'm going to let it sit a day or two and see if fuel drips out of the crankcase drain opening, then I'll know for sure if fuel is going into the crankcase. If the fuel is holding in the the air filter housing then we'll see where it's going to go. Perhaps the air filter housing has to fill to a certain level before the fuel will then drain into the intake manifold and through to the crankcase. I can loosen the intake manifold bolts and see if that's happened.

I'm going back to that solenoid. If that solenoid is supposed to send a plunger up into that center opening to stop it up whent the engine is off then that might explain how the fuel is getting past the needle valve.

Can someone tell me what should happen if I can remove that solenoid from the bowl but leave the wires connected? Does that solenoid operate, as in continuously on/off/on/off while the engine is running, or is that solenoid in one position while the engine is on and then another when it is off? If that is the case, can I remove the solenoid from the bowl but leave it connected and then turn the ignition key on, should I see a change in the solenoid position or does the position only change when the engine is actually running?

Did a little more research a la You Tube, pretty confident at this point that I have a faulty fuel shutoff solenoid. I'll test it in the morning and see if the solenoid is bad or if there is a wiring problem. Thanks for those who attempted to help!

I fail to see how the fuel solenoid could cause this problem at all. The float, float needle, and seat keep the fuel sealed off from entering when working properly.

That's what I thought but that solenoid is actually called a fuel shutoff solenoid, when the engine is turned off it allows the plunger to extend into the fuel nozzle to prevent any fuel from passing. I check and my solenoid is good but I think gunk in the seat caused that solenoid from seating properly. I cleaned it up and I'll see what happens.

True but the plunger is only affecting the fuel to the main jet, plunger doesn't have a 100% seal to the main jet. Fuel is still traveling thru float needle into carb(assuming bowl isn't full) just not to the main jet. People have cut the plungers off and some have bypassed them altogether.

Mikel1 said:

True but the plunger is only affecting the fuel to the main jet, plunger doesn't have a 100% seal to the main jet. Fuel is still traveling thru float needle into carb(assuming bowl isn't full) just not to the main jet. People have cut the plungers off and some have bypassed them altogether.

Click to expand...

True, & even with it working properly if something gets stuck in the needle valve off the float, gas will still enter the engine. This happened to my old craftsman 46".. That's why I also added a fuel shut off valve..