312-8 dies after 45 minutes of mowing

[truckin88 104]

My dad's 312 has never given an issue but for the 2nd week in a row it has died after 45 minutes of mowing. It will start after sitting for a bit. Any ideas?

[rmaynard 16,289]

The first thing I would look for is a blocked vent hole in the gas cap.

[SolarStallion 38]

I have the exact same tractor. Mine was doing that this season. It had good spark and compression. I thought it may be a fuel issue. Turns out my fuel pump was going bad. I replaced the fuel pump and it runs fine now.

[1maidenfan 202]

I am dealing witht he same thing on my D160 with a 16hp Onan. I am leaning towards the fuel pump, going to change over to an electric fuel pump and see what happens.Here is the part number for the pump the guys on here use on their tractors.

Facet posi-flo Part # 610-1051 1.5-4 psi

Check ebay or any parts store.

[Duff 206]

Hi, Will,

Somehow missed this thread. My money's on a bad fuel pump as well.

Duff :thumbs:

[tunahead72 2,543]

Seems like there's a bunch of these "stalling after xx minutes" threads lately, here's one that might give you some ideas:

It COULD be your fuel pump, or any one or more of several other possibilities. I personally wouldn't go to the time and expense of replacing mine until I tested it. You can just remove the end of the fuel line where the pump connects to the carburetor, try to crank it and see if you get a good healthy spurt of gas (do this carefully, please).

I believe it was Chuck (SOI) who suggested replacing that short section of fuel line with a clear line, so you can see whether you're getting fuel from the pump without having to remove anything. Sounds good to me.

[Save Old Iron 1,571]

I believe it was Chuck (SOI) who suggested replacing that short section of fuel line with a clear line, so you can see whether you're getting fuel from the pump without having to remove anything. Sounds good to me.

I have used that idea several times to find leaky pump diaphragm and even pin hole leaks in fuel filters. Although I have used clear TYGON brand tubing temporarily on a fuel delivery system, once the problem is resolved, revert back to tubing intended to be used as fuel line.

Recently I have noticed many inexpensive fuel filters have more manufacturing "flashing" around the seam lines of the molded plastic bodies. This excess plastic can prevent the fuel line from making an air tight seal with the inlet of the fuel filter. The fuel pump finds it easier to draw air in around the flashing than draw fuel up from the gas tank. The fuel filter slowly fills with air and starves the pump. Pin hole openings can also develop around poorly molded filter bodies.

Another tip - as less expensive filter media is used in fuel filters, the filter paper becomes increasingly hydrophobic (dislikes liquids). I have seen where only a small portion of the filter paper "wets up" and allows fuel to pass thru the filter media. This can also starve a fuel pump. Filling the fuel filter half full of gas, capping the ends and shaking the filter sometimes resolves this condition. I have used alcohol in some stubborn filters to fully wet the paper, then gasoline will flow thru easier.

[handyman 1]

Going a different direction than fuel...Shortly after I got my C141, it would do the same thing. It would act like you shut the gas off after about a half hour of mowing. It turned out to be the coil. When it was hot, I pulled the wire off and the well down inside was full of oil. The next time it happens, have one of those inline spark plug testers handy to see if the problem is fuel or spark.