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Engine only running 20 seconds to a minute


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Posted
A friend of mine is asking for my help "Diagnosing his engine problem" on his Simple Tractor with a 300421 12hp Briggs & Stratton engine (lives in NC so I'm helping remotely). Here's what he wrote me: Now I can get it to start up using the started spray. It will run in either idle or in gear anywhere from 20 seconds to 1 minute, then it will spudder out on me. I also noticed that when I add the starter fluid or gas. there is a hole in the pipe between the carcurator and the filter that does not have a screw in it. It is on the bottom of the pipe and it is under the part on the pipe that says choke. I think he's talking about the drain hole verses the breather hole which I first thought he was speaking about. I'm first guessing it could be a fuel supply problem; any tests I should suggest to him? Note: I expect one day he'll join this site, but he's too busy these days to get "involved." I've also sent him some suppliers lists, which advertise on this site.
Posted
Check the fuel tank for any blockages around the screen thats in the tank. I remove the screen that is in the tanks on my tractors and put a inline filter in them. My 917H had a screen in the tank and last summer I thought that I was having carb problems and I rebuilt it because I would always have to mess with adjustments. One morning I went out to the garage and there was gas all over the floor because the tank bushing started to leak. When I removed the bushing the filter screen was plugged. Removed it and haven`t had a problem since.
GWGAllisfan
Posted
If the fuel tank and line are clear, then it could be a float sticking.
Posted
The hole is a vent where excesive gas that might collect can drain away. Most of the time there is a piece of felt in the hole to prevent unfiltered air from entering. Now if squirting gas or fluid into the carb will let it run then it's a fuel flow problem. First off pull the fuel line where it goes into the carb. and see if there is flow. If it isn't, find the flow restriction. If you have flow then replace the line and remove the needle. My guese is that there is water in the bottom of the bowl and draining whatever is in the carb and flowing fresh gas into the carb should restore it to running provided that the water didn't have time to create a lot of debris and gum. It was raining when he left here and he could have picked up some water on the way home or it could have been condensation buildup if he's just now getting into it.
Posted
I agree the first thing to do is remove the screen in the tank outlet. When he does, have him install an inline filter AND a fuel shutoff between the tank and the inline filter.
Posted
When I first started my rebuilt Briggs last week, I had the same problem, exactly! I thought maybe timing, as I had had the mag off, and possibly located it in the wrong 'spot' when replacing it. Jostling the tractor while pulling the motor must have moved some of the tank garbage, and I was able to cut grass on Sunday. Yesterday, it ran about 3 minutes and died, still had spark, but would only run on the choke. In a pinch, I tried blowing back through the gas line. Ran perfect for a tankful of gas. I do have an inline filter, and noticed that gas was not present in it, hence blowing out the line. Tell your friend to remove his gas line at the carb,if there is no gas flow, blow back through it into the tank (remove the cap on the tank, first) to clean the line of debris. If it runs after that trick, his next item is as described above by Ray, to remove the in tank screen and install an inline filter.Always be sure to have a fuel shutoff, whether below the tank or inline. If he has flow, the needle is sticking, may need replaced, or the needle is simply stuck by varnish deposits, and can be cleaned with any good carb spray and replaced. If the needle has a 'shoulder' on it, replace the needle.
Posted
I've had this happen before with 2 & 4 cycle engines,Try turning the needle in and out a few times,it might have a small bit of grit hung up and blocking the flow,then follow mrsteele's advice. so far i've polished 3 needles that were grooved and they work fine.
Posted
Thank you for all the replies: I'll update you all after we try some of these tests. My friend is really busy working a new job and didn't expect to be able to try anything until this Thursday. Again-THANK YOU!
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