John deere lawn mower weird cutting out

[pete cutting]

i have a john deere lawnmower with a briggs and strapon intek v-twin engine. It has a habit of dying and not restarting unless you remove the air filter and put your hand over the intake. My first thought was a split in the plastic intake manifold but after replacing that i still have the same problem. Sometimes it does this weird thing two or three times and then run fines for an hour or so, allowing me to get all the grass cut, Othertimes it just won't run longer than about 30secs.
i have replaced the original fuel pump with an electric one and it's still the same. there is fresh fuel, new filters and i've ran it with the fuel cap loose and it still does it. i have also taken the fuel pipe off just after it cuts out and blown down the pipe to clear any crap that might have been on the pick up but it changes nothing. I can't see it being electrical because it starts as soon as you block the air intake intake. It does seem like it's pulling air in from somewhere, just not constantly as it will run ok at times other than a crack/split in the plastic manifold expanding and contracting I can't see anything that would cause it. But as I've said that been replaced and all the inlet gaskets. other than a gallon of petrol and a match does anyone have any ideas how to fix it?

Thanks PC

 

[tom3]

Failing solenoid on the botton of the carb fuel bowl? Piece of crud or drop of water in the carb. float bowl that gets sucked up to the main jet, falls away when the engine dies?

 

[bertsmobile1]

I will agree that you have a fuel problem from what you are describing.
Have you fully dissasembled the carburettor and cleaned it out thoroughly ?
The twin barrel Nikki is a bi finicky and prone to blocking jets
You will fine plenty of You tube videos if you search "Nikki twin barrel Briggs carburettor "
There is a good photo description of how to clean them on the Outdoor Power Equipment site
I do not know why but crub tends to build up under the top plate and block the holes .
Also worth checking is the fuel shut off solenoid.
From memory it is 5/16 UNF but take the bowl to your friendly nut & bolt supplier and get a short bolt and alloy washer or a threaded blanking plug to fit in the hole.
Fit that and see if the problem goes away as that is the easiest thing then if it does no better strip down the carb.

There are a few variations of these carbs and be very careful not to mix up the jets, they look the same but are different sizes and it will run like a drunken billy goat if you mix them up as one cylinder will be lean & the other rich.

 

[pete cutting]

Thanks for the replies. I don't think its the float getting sucked up as it isn't consistent. If it was getting sucked up and dropping when engine dies then it would start almost straight away whereas the only way to start it is to block the air inlet. I've actually ran it with a piece of cardboard blocking the inlet , when I removed the cardboard the first time it died. it only restarted when I refitted cardboard and it started straight away and ran fine. I left it in place longer and when I removed the second time it kept on running. I finished cutting the grass, which takes about 90mins. Next time I went to use it the same thing happens. I can't see how blocking the inlet would bypass a faulty cut-off solenoid.
i will strip and clean the carbs and see what that does. thanks again.

 

[pete cutting]

I forgot to mention that the carb fitted isn't a twin barrel carb, It's a single barrel nikki with a horizontal butterfly spindle and the fuel cut-off enter through the side of the float bowl. I've looked through the internet and can't find anything that is exactly the same. most have a vertical spindle and the cut-off entering from underneath the float bowl. It definitely has nikki cast into the body just behind the fuel delivery pipe and a set of three numbers stamped on the top of the body..593197, GO2923, 5620. It also has either 1-2 or I-2 casted on one side of the body. I've checked the cut off and it works even when the wires are jiggled about. the jet is clear as is the emulsion tube.
The float chamber has a plastic cover(?) on it which I can't get off and I'm not about to attack it with a knife or screwdriver in case there's a knack to removing it. Does it twist off or is it just a case of using something thin to prise it off.

 

[tom3]

When you put your hand over the air intake you put full engine vacuum on the whole carb, could loosen or suck through anything that gets lodged in the main fuel jet passages or supply.

 

[pete cutting]

When you put your hand over the air intake you put full engine vacuum on the whole carb, could loosen or suck through anything that gets lodged in the main fuel jet passages or supply.

i thought of that however the new filter is clear and until I get this part off the float bowl i can't see how clean it is in there.

 

[pete cutting]

Fixed it atlast!! Having gone through everything I could think of and some I couldn't I employed Sherlock homes to assist me. Good old Sherlock said to me " When you have eliminated the impossible, whatever remains, however improbable, must be the truth?”
So it was highly improbable that it was the filter as it was a new one fitted just after the first incident and didn't have any effect at all. I removed it and cut it open to see inside and there was enough grass cuttings in there to block the filter, but when it was stationary they dropped off the mesh and allowed enough fuel flow for the engine to run before being sucked up again blocking the filter once more.
With the new transparent filter I can now see if it clogs again, so far it hasn't. If more grass appears in the filter I'll whip the tank off and give it a good clearing out. I reckon that with my hand over the intake it was drawing fumes up from the tank through the breather, enough to get it running until the filter cleared itself
I can only assume either my son or daughter didn't clear the cuttings from around the filler when refueling it.....or worse than that I forgot to remove the grass.

 

[bertsmobile1]

Thanks for this .
Usually the in side of a filter is the outside so you can see how much debris is in the filter.

 

[pete cutting]

Thanks for this .
Usually the in side of a filter is the outside so you can see how much debris is in the filter.

In this case the OEM filter was white plastic so couldn't see inside. Ive replaced it with a transparent one so Ill be able to keep an eye on it from now.