OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk carby leaking fuel - mechanically challenged :-)

Hi

I have been having on going issues with old rover rancher with 12HP B&S. I have given up taking it to shops they just seem to "patch up" rather than fix things properly and tell me what is really wrong..If I didn't know any better they want to spend as little time on the each job and get as much money as possible, or is that just my cynical side talking??

Anyway, replaced the battery today (old one was cactus) and then noticed fuel leaking from carby. I pulled a few things off to see what was going on and I found a little rubber "Z" shaped hose had come off from the carby.. see pics

My question is, what is this little rubber hose for? the fuel obviously goes down through the metal body towards the spark plug....

I have pushed the hose back on but I suspect it is going to come off again given the vibration from the mower and the terrain I mow

Thanks
Nathan

I can't really see it properly, but it is not the fuel hose, which will connect to the fuel tap on the opposite side of the carburetor. The hose you have outlined in yellow seems to be the crankcase breather. This means it is part of the system that sucks air through the bottom part of the engine, mainly to keep water from condensing there and contaminating the oil - but it also removes hydrocarbon fumes, and passes them through the combustion chamber to burn them, thus preventing air pollution. If I'm right and it is the breather hose, it should not have fuel in it, but it is bound to have dirty black oil in it, and the oil will drip out if it is disconnected. The carburetor looks like a one-piece flo-jet.

thanks for the explanation :-)

the fuel was coming out of the carby where the breather had come off.

I will put it all back together and see if it goes.

Nathan

Fuel should not come out from the carburetor's breather port. It sounds like there is a problem - possibly the carburetor is flooding. When you have fully assembled the engine, with fuel in the tank and the fuel tap in the on position, disconnect the breather hose at the carburetor end. If fuel runs or drips steadily from any part of the carburetor, it sounds as if there is flooding, which is probably due to a needle-and-seat problem. Incidentally the breather hose probably fell off because of the fuel getting inside the hose, which makes it very slippery.

I would suspect that maybe one of the following is occuring to have the fuel leak like that.

Worn or dirty float valve seat. (In that circle shaped bowl on the bottom of the carby, there is a float with a little needle running off that, its possible there is a bit of grit on that needle or its seat and allowing fuel just to keep running in.)

The float has a hole in it, (Once again in the bown under the carby, the little brass coloured float may have got a hole in it and sunk to the bottom aloowinf more fuel to rush in.

Lastly, maybe the choke is stuck on, floodying the carby and it is running back?

hmmm, how do I go about pulling the bowl off the bottom to check the needle etc? do I need to remove the carby assembly from the engine or is there an easy way?

could this be caused by contamination in the fuel? when I drained the tank the fuel did not run out of the hose as fast as I would have expected so could be some gunk in the tank and/or hose?

Nathan

G'day Nathan, there is a bracket behind the breather hose you are talking about, if you take out the screw at the top of the bracket and push the bracket away then slip the breather right on, push bracket back in place and screw it on. That will stop it from slipping off in future. As far as fuel coming out of the carb at that spot, is the motor running at the time? is it slow drip? fast flow? i know some of mine build up fuel in the back end. could be an intake valve problem. One carb sprays out fuel out the air filter hole. Got a leaking intake vale causing that. Anyway, shoouldn't be much to fix by the sounds. start with the bowl/float/needle & seat as mentioned, if they were any sort of mechanics they would have sorted it.
Gary

thanks Gary, I recall thinking to myself that bracket is not helping the hose stay on :-)

Any tips or instructions on how to strip a carby down?

I make my living with IT but I am keen to learn more about this stuff now that we are on 5 acres and I am going to have to rely on my equipment more..

And yes, I would have thought this should have been sorted considering the carby was serviced (apparently).. So if you want something done properly you do it yourself, with guidance when required!

Nathan

Yep, i think that's partly why the bracket is positioned right there. If you PM me i will step you through it.

Nathan_O,

If you know the model and code click HERE and you will be able to get a parts list to start with as well as other information.

I would remove the two screws that hold the carby on to the engine block so that you can easily work on the carby without to much trouble. It sounds like to me that the carby may have dirt in it or the float is damaged.

thanks everyone. I will let you know what I discover when I have some time to work on it again

Nathan

I suggest you begin by verifying that the carburetor is flooding, as explained previously. If it is, there are two likely immediate causes, as Joe said: either the needle and seat is not closing properly, or the float has sprung a leak. In my experience the needle and seat not closing is the more likely problem, and it is usually due to dirt under the needle. The dirt comes in from the fuel tank through the fuel line. You need to clean out the tank and line, and verify a steady flow of clean fuel out of the fuel line. Once that is done, you will need to clean out the carburetor, which is a bit trickier and more delicate so I suggest you do these preliminary steps first. (It would also be irritating to clean out the carburetor, put it back on the engine, turn on the fuel, and refill the carburetor with crud from the dirty fuel tank.)

yep, planning to clean the tank and fuel line. I assume I just take the tank off and flush and any rubbish with some petrol?

I still need to work out how to get the needle, a bit of a learning curve for me...

Any ideas on where abouts the engine number will be stamped? Just had a quick look and I couldn't see anything, perhaps it is covered by something else and I have to remove it to see the numbers.. will clean out the fuel tank and line tonight.

Nathan

As well as flushing the tank, you need to clear the outflow fitting where the fuel line connects to the tank. Some engines have a mesh filter there - I don't know whether yours does. If there is a filter, remove and clean it then reinstall.

To get to the needle you need to remove the float-bowl. Your carburetor is called a 'small one-piece flo-jet'. You remove the float bowl by unscrewing the hex nut at the bottom of it. However as Bruce said, you should remove the carburetor to do this - it is a delicate process and you could do more harm than good if you try to do it without being able to see properly.

The attached pictures show the parts of your carburetor. The float bowl is the roughly-hemispherical part at the bottom, retained by a nut in the center. There is a fragile gasket between the nut and the bowl - don't wreck it.

The engine's model, code and serial number are stamped on the tin air cowl that directs cooling air from the flywheel fan around the cylinder head. It is in the form of flour blocks of numbers. The first block is the engine size and type, and the third is the year and month of manufacture. The other two blocks are more or less inscrutable.

OK, so I have taken the tank out and it looks pretty clean to me. only a very small hole for the fuel to come out so that would explain why it didn't flow out of the hose as fast as I was expecting. There is no filter at the tank, would it be possible to install a standard inline type fuel filter to try and help protect the carby from gunk?

found the engine details too
model 281707
type 0151-01
code 88122331

anyway, I have taken the carby off the engine and removed the float bowl. Here are a few pictures. not really sure what I am looking for..






so what do the pictures tell us?

talking to one of my neighbors tonight they suggested that perhaps the valve is jammed shut not allowing fuel in to the engine and perhaps that is why it is coming back in to the first part of the carby body?????


Nathan

Excellent pictures - that makes the discussion way more useful.
First, holding the carburetor the right way up, gently raise and lower the float (the hollow brass toroidal thing at the bottom). Look near the pivot: you will see the needle (a brass object clipped to the float's pivot arm) going up and down with the arm. We need to inspect where the invisible pointy bit on the top of the needle, seals against the carburetor body (the tiny toroidal part where it seals is called the seat). Turn the carburetor upside down, slide out the float pivot, and lift off the float. The needle should be clipped to it, so it will come out simultaneously. Now you can look at the seat, and clean out the passage to the fuel line. Inspect the seat for any dirt or damage (corrosion, scratches, or being installed crooked). Look at the part of the needle that seals against the seat. Look at the float: does it rattle or splash when you shake it? Is there any sign of a leak in the solder joint around it? When all is well, reassemble the float and needle. Hold the carburetor upside-down, so the float is in the 'up' position: is it parallel to the carburetor body? If it is, all is well. If not, tell me and I'll explain how to correct it. Do not try to correct it by just pushing on the float - that will mess it up.

Now it's time to clean out the rusty float bowl. Was the engine running properly aside from the flooding? If so, you can now reassemble the carburetor.

Having seen your new pictures, it seems you actually have a large one-piece flo-jet, not a small one-piece flo-jet. The adjustable device that holds the float-bowl on is actually your main mixture adjustment - see pictures.

Try not to change the adjustment of the bits in your first picture (i.e. rotate the brass screw in relation to the hex nut). We'll get to that when you are ready to tune the engine.

I don't recommend an in-line fuel filter because they add more stuff that can cause you trouble. The best solution is to keep dirt out of the fuel tank. If you want to add a filter (Ryco make a range of them IIRC) make sure it is not exposed to heat (which would cause vapour lock), is big enough for your engine size, is properly supported, and cannot cause a fire hazard. See why I suggest you refrain from fitting one?

I think this is going to take a while

Thanks again, will do as you have suggested and take some more pics along the way.

Nathan

what's the best way to clean out the rust in the fuel bowl bit? just some steel wool or something???

Whatever works, Nathan. On flattish surfaces I like to use a scraper because it is fast, but your rust looks shallow in the picture, and I'd rather not remove more of the plating (if there is any) than necessary. Hence a hard plastic pot-scrubber would be great if it works. If it doesn't, steel wool. If it turns out quite a bit of the plating is gone anyway, then some kind of steel scraper is quick and effective.

In case it is useful your engine is 28 cubic inches displacement (460 cc) and was made in December 1988. AFAIK those larger engines were still made in the US, and with cast iron cylinder liners. If so it is probably a good one. So far I don't see why your mower repairer wasn't keen to nurture and cherish it. Maybe it has some dreadful communicable disease than only he knows about?

I have been told that it's a good one and I should keep it as it will last forever. I do want to learn this stuff, I appreciate all the assistance!!!!

I checked the needle and seat. was a tiny bit of stuff there and got that out. all looked OK from what I could see.

Think the float bowl gasket might need replacing though, see pic. only $5.59 anyway.

Also not sure about the thread tape that has been used on the fuel tap. I think bits of that might have been getting in the way of the needle/seat. what should be used rather than tape? is there a threadseal type product that can be used?

when upside down the float seems to be in the right spot. No sign of a hole in the float.

Can't seem to clean the rust out of the float bowl so perhaps a new one of those would be a good idea??? Not sure how much they are, the search function on the store seems to be having problems when I try and search for the part number 221995.

The gasket needs to have a continuous surface all the way around the float bowl. In the picture it looks either dirty or discontinuous. Teflon tape is usually pretty harmless, because if you put in on properly it does not project past the front of the thread. However yours seems to have been very badly applied. You could use liquid thread-sealer, or nothing - it shouldn't really need sealant, but if you want to end up with the tap horizontal or on any non-random angle, you will need to do something to help it slip. I think I'd try liquid thread-sealer, which you should be able to get from an automotive shop.

There is no need to remove all the rust from the inside of the float-bowl, you just have to make sure there is no loose rust. I'd give it a scrape, wipe it clean, and forget it unless it's badly pitted. No need to replace it.

Can you confirm that the engine was running well at the beginning of this process? If it wasn't, you need to clean out the carburetor - remove jets, blow air through the drillings, reinstall jets. I prefer not to disturb such things if they are already clean, but in this case there could be loose bits of teflon tape all over the place. Your mower guy seems to be more of a plumber than a motor mechanic. If you want to strip the carburetor, you have to note the initial setting of the adjustable idle mixture screw so you can put it back in the same position.

the engine was running OK before I had this leaking fuel issue which was leaking from the where the breather tube had come off.

then last time I tried to start it, after putting in new battery, there was a small puff of smoke, I assumed it was some wiring insulation given the length of time I was trying to start it. But will see what happens....

if you look at the photo using this link you can zoom in
http://picasaweb.google.com/lh/photo/UuLaEu1xljU9rhHSud2y8A?feat=directlink

part of the gasket is protruding on the outside and some on the inside, if that makes sense. I am not sure how it should look when seated correctly. I am keep an eye on it, if it is not sealing then I expect i would see fuel leaking around there.

so i will put the carby back on the mower and get the tank and fuel line hooked up. I'll remove that red tape off the fuel tap and use some new tape and no go past the end of the thread...

might as well give it a burl and see what happens.... might check the exhaust and make sure I am not providing a cosy location for a wasp nest.

Nathan

The top gasket around the float bowl does not have to hold pressure - it is there to keep fuel from slopping out when you run over bumps or work on a slope. It looks more squished than torn or chopped. However it mustn't leak - loose fuel around a running engine is dangerous, especially when it's right under your backside. The safe way to go is to reassemble the carburetor, fill it with fuel, and try a bit of shaking and tilting to see if liquid fuel leaks out. Then, either before or after putting the carburetor back on the mower, turn the fuel on with the carburetor the right distance below the fuel tank, and fuel in the tank. Wait ten minutes and see if it floods, drips, leaks etc. If it doesn't emit any fuel, it's time to crank up the engine.

Do you have the owner's manual, to find the correct way to start the engine (use of choke, etc.)? Old Briggs engines are very easy to start if everything is working and if you follow the manual. Does it crank at a sensible speed? Some of the larger Briggs engines have automatic decompressors, and if they don't work the engines are difficult to crank, overheat the starters, ruin the batteries, and sometimes cook the wiring.

hmmm a manual, no don't have that. I am the 3rd owner apparently or maybe the 4th. before I had it, it was used to tow small helicopters around a little airport, so I have a orange flashing light on the bonnet (but like the other lights it doesn't work)

I will try the fuel into the carby trick. so no fuel should leak out anywhere correct, not even the end that connects to the engine?

Nathan

When you are doing the swishing-and-tilting test (technical term) you should put your finger over the fuel hose connection on the carburetor. Don't tilt it beyond a normal tilt-angle for safe operation of the mower. In that test you are only looking for wetness on the outside of the float bowl, due to fuel passing between the carburetor body and the top of the float bowl.

When you do the static fuel pressure test (fuel hose connected, fuel on, carburetor level, watch for ten minutes) there should not be any fuel comes out of anything. The float bowl should fill, the float should shut off the needle-and-seat, and then nothing should happen except the grass keeps growing.

Now that you have found the model numbers and codes, you should follow Bruce's advice from early in this process and check in the parts and manuals section of this site. There may be an owner manual there - I don't know. Because your engine has a manual choke (mine is automatic - <<smug mode on>>) you can easily prevent it from starting, or running decently, just by not choking it when you should, or choking it when you shouldn't. As Joe said at the beginning, you might even get it to leak petrol from the breather tube if you over-choked it then stopped it.

I think my mower has the wrong muffler fitted to it. The one on there is this one https://www.outdoorking-forum.com.au/index.p...ath=193_195_375_526&products_id=2268

But from according to the parts list I downloaded when my subscription was valid I should have this one which seems a lot bigger https://www.outdoorking-forum.com.au/index.p...ath=193_195_375_526&products_id=2262

Not sure of the differences between these two mufflers other than the physical size, just wondering if the smaller one is providing too much resistance that could be causing a problem??

Nathan

A moderately smaller muffler will only slightly reduce the maximum power (perhaps by one hp or a little more), it won't affect the way the engine starts or runs. When you get everything else working properly, a muffler upgrade might make you feel better (I admit it would make me feel better if it were mine) but you seem to have more important things to do first, in my opinion. Meanwhile I'm wondering how you control the choke - is it done with a control rod reaching outside the engine compartment? Does it open fully and close fully? Is your carburetor now leakproof? Have you checked the intensity of the spark?

ran out of time today. I will try and do the carby "slosh" test tomorrow and post the results. Once the carby is back on I will take a video of the choke operation :-)

Nathan