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Discussion Starter #1
Engine slowly became harder to start and keep running, had to fiddle with choke and gas lever to keep running. In 2016 when I bought the machine I rebuilt the carb, installed new fuel lines and fuel filters and cleaned the tank but never changed the fuel pickups. Last week I pulled the top off the carb cleaned inside was not too bad. Removed main jet and cleaned and the small jet inside the carb. Also replaced the 2 fuel filters with new ones from Napa which looked about the same size. Also replaced the tank pickups and gromets. Now engine starts but only smooth with the choke partially closed. I can see the gas pouring in from the main jet and after a minute or so it starts surging badly and I can see the fuel surging into the throat of carb.
There was not much gas in the engine fuel filter before I started so I filled it with a water bottle of gas. It stayed filled through the surging.
Not sure where to go from here. Could it be the new inline fuel filters or I screwed something up in the carb...??? Any help is appreciated.
 

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You need to do the propane test around the intake manifold. Run the engine and then use an unlit torch and allow some propane to flow then move around manifold. If it stops surging then you have a manifold leak; fairly common issue on the 318's.
 

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AKA Moses Lawnagan
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You need to do the propane test around the intake manifold. Run the engine and then use an unlit torch and allow some propane to flow then move around manifold. If it stops surging then you have a manifold leak; fairly common issue on the 318's.
Are the manifold leaks usually due to cracks, or gasket seal at the carb base or cylinders? Is that also an issue on the 420?
 

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Kish JD 318/420/430
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The manifold is a two piece that has a silicone/rubber seal and is riveted together. It is that seal that is the one that is over looked. The other can also be checked the same way though.
 

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My 318 had a crack in the manifold when I got it. Look at the manifold carefully and make sure the mount that supports the air box is intact. Mine was broken also.

Another place to check is the linkage for the governor. Mine had enough slop in one hole that it would surge like crazy. I had to move the rod into the next hole on the plate and the surge went away. That changed the motion ratio of the linkage so from then on I only used half of the range of the throttle lever.


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John, I very well be one of the above issues, but this would not cause fuel to surge out of the main jet. I'm thinking when you dismantled the carb for cleaning, something got in there or it didn't go back together correctly...I'm thinking the needle/float asm or something in that area. Could even be gasket is preventing float from rising enough to close needle.

Fuel filter: The inline filter on my 322 stays 1/3-1/2 full all of the time. Filling yours full may (??) be an issue, not sure. I'd dump gas out until 1/2 full and see what happens. Bob
 

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Discussion Starter #7
John, I very well be one of the above issues, but this would not cause fuel to surge out of the main jet. I'm thinking when you dismantled the carb for cleaning, something got in there or it didn't go back together correctly...I'm thinking the needle/float asm or something in that area. Could even be gasket is preventing float from rising enough to close needle.

Fuel filter: The inline filter on my 322 stays 1/3-1/2 full all of the time. Filling yours full may (??) be an issue, not sure. I'd dump gas out until 1/2 full and see what happens. Bob
I'm just heading back out to the garage this morning and saw your update. Interesting in that after I changed the fuel filters, the one at the carb only had little fuel in the bottom and I was pretty sure sure it use to be around 1/2 full before I changed. I'll check that one first as the easiest and then move to the manifold. Because I was having some surge before this started, it just might be a leak. This is what keeps us up at night!
 

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Discussion Starter #8
I lowered the fuel level at the filter in front of carb to about 1/2. Using my map gas propane touch I held the trigger to just before light so gas would come out without lighting (sometimes:) ) and tried to point to acessable areas of the manifold while the engine was surging. No difference. Also, from what I could see the manifold looks like one piece from base of carb out to the inlet ports. Have to pick up grand kids. I'll try again later this afternoon. Thanks all.
 

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Discussion Starter #9
My 318 had a crack in the manifold when I got it. Look at the manifold carefully and make sure the mount that supports the air box is intact. Mine was broken also.

Another place to check is the linkage for the governor. Mine had enough slop in one hole that it would surge like crazy. I had to move the rod into the next hole on the plate and the surge went away. That changed the motion ratio of the linkage so from then on I only used half of the range of the throttle lever.


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I'm not sure what the airbox is, is that where the base of the carb is mounted to the mainfold? I guess I would need to remove all the sheet metal to check the manifold for cracks.
I checked the governor linkage and it is very tight.
 

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Kish JD 318/420/430
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Airbox aka the air cleaner box. It sits on top of the carb and holds the air filter and prefilter. There maybe a plastic shield to keep things from falling into the carb throat also.
 

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I lowered the fuel level at the filter in front of carb to about 1/2. Using my map gas propane touch I held the trigger to just before light so gas would come out without lighting (sometimes:) ) and tried to point to acessable areas of the manifold while the engine was surging. No difference. Also, from what I could see the manifold looks like one piece from base osf carb out to the inlet ports. Have to pick up grand kids. I'll try again later this afternoon. Thanks all.
The manifold is split horizontally. Top and bottom halves are bonded/riveted together. If leaking, one can drill out the rivets, replace the sealant and replace rivets with small screws and nuts.

John, I very well be one of the above issues, but this would not cause fuel to surge out of the main jet. I'm thinking when you dismantled the carb for cleaning, something got in there or it didn't go back together correctly...I'm thinking the needle/float asm or something in that area. Could even be gasket is preventing float from rising enough to close needle.

Fuel filter: The inline filter on my 322 stays 1/3-1/2 full all of the time. Filling yours full may (??) be an issue, not sure. I'd dump gas out until 1/2 full and see what happens. Bob
That surge is probably caused by the governor opening and the main jet delivering fuel as a result. The governor opening is probably because the idle jet is plugged. Throttle opens, gets a shot of fuel, speeds up, throttle closes to idle setting, speed slows because of the plugged idle jet. Over and over and over and...

That's my guess based on seeing those symptoms more than once, a lot more.
 

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Discussion Starter #12
The manifold is split horizontally. Top and bottom halves are bonded/riveted together. If leaking, one can drill out the rivets, replace the sealant and replace rivets with small screws and nuts.



That surge is probably caused by the governor opening and the main jet delivering fuel as a result. The governor opening is probably because the idle jet is plugged. Throttle opens, gets a shot of fuel, speeds up, throttle closes to idle setting, speed slows because of the plugged idle jet. Over and over and over and...

That's my guess based on seeing those symptoms more than once, a lot more.
That is exactly what I see happening. I'm not sure which jet is the idle jet. I turned the large knurled screw with spring around it which is mounted near front base of carb open one full turn. It seemed to smooth out a little but then started again. I am just going to buy a carb rebuild kit and disassemble and clean good. My carb model number is 6100 146-0412. I'll keep everyone posted. Thanks
 

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John, I bought a 322 about a year and a half ago and it ran pretty poorly...to put it politely! I narrowed it down to the carb, got a rebuild kit from my JD dealer, and stopped at NAPA on the way back. They have a container of carb cleaner, about 1 gal., with a parts basket in it. I dismantled the carb, put all metal parts in basket, and let soak for 2 days. As I removed the parts from the basket, I blew them off with air, then rinsed with brake cleaner. Last, I used a can of compressed air to blow out all the tiny holes in the carb body. Reassembled it and it runs great. Bob
 

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Discussion Starter #15
My son who is pretty good with small (and large) engines came over yesterday and we spent some time looking the 318. He sprayed carb cleaner around the intake manifold for as much as we could see with the sheet metal on it, to check for leaks and could not find any. We pulled the top off again and cleaned out the small jet, checked the float and needle valve. Tried adjusting the air mixture screw. The governor linkage is very loose when the engine is off but when it runs there is no slop. Going to pull the top off again today and remove the inlet fuel line and needle valve and blow air into the port just make sure there is nothing blocking the flow. If that does not work I'll get a rebuild kit from Boomer and give the carb a good soaking and rebuild. Runs pretty good at 3/4 closed throttle, does not seem to be getting a steady flow of enough fuel.
As long as the snow (I hate saying that word) holds off I don't need the tractor. :)
 

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John, In your first post, you stated you didn't change/clean fuel pickup in tank. I believe (??) there's a screen on the end of the pickup. This may be restricting fuel flow for full throttle operation. Also, if you haven't already tried this, loosen or remove gas cap and see if it makes a difference. Bob
 

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Another issue these carbs has is the plug in front of the carb becomes loose and causes surging,it’s not big but it covers a drilled passageway,if you find it just put ur finger over it While running and you can tell if it is loose,it will start to smooth,might not be the issue but checking it will eliminate one issue
 

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Discussion Starter #20
SUCCESS!

It was the plug in the front of the carb above the air fuel mix screw - it is missing! I put my finger over the hole and the machine settled right down....... I had called Boomer this morning about a rebuilt kit for the carb and he said why do you want that and then the lesson began :)

Now I just have to try to reach him again about getting a new plug.

Thanks to all for your help, it was an interesting lesson and I learned a lot. Probably at my age, next time it happens I won't remember what I did.:laugh::thanku:
 
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