Riding mower runs for about 20 mins then stops

[JP98]

Two things to check the next time it happens. As soon as you feel it starts to quit open the gas cap. If it continues to run, your gas cap is bad, vent plugged, and needs to be replaced. If this is not the problem, purchase an inline spark tester, and check for spark as soon as it quits. No spark coil has either a hot short or hot open and the coil needs to be replaced. Let us know what you find.

Ok, so it's not the gas cap. I tried to cut the lawn today and sure enough, 15 mins into it, it started to sputter. I immediately open the gas cap and it made no difference. It still quit. I got my inline spark tester and I got sparks. But maybe by the time I got my tester from my garage and walk back to my mower, it must have been about 5 mins. Maybe enough time for spark coil to cool down??

I'm going to order 2 new spark coils, spark plugs, a fuel filter, and a fuel pump. Easy enough to change the pump and filter so if those are the culprits, I'll return the spark coils. Amazon Prime cost me nothing to return them anyway.

 

[slomo]

Other guys have good suggestions.

Normally when time comes into play, mower dies after 15 mins, trash in the fuel tank. Could be a weak ignition coil getting hot failing.

It starts to sputter like it's running out of gas then quits.

Sounds just as I and the others described.

 

[Auto Doc's]

I believe the fuel tank pickup line is going to be the issue. They collect debris over time and it is very subtle for it to gradually choke up and restrict fuel flow. When the mower shuts down, the "stuff" relaxes then allows fuel flow for a short time until it acts up again.

There are a very few machines that have a screen on the end of the pickup tube, but sediment will even get through the screen eventually.

The strangest fuel restriction I have seen was a Cub Cadet Z-Force that actually had a 90 degree elbow with a worn plastic shutoff valve. Right at about 15 minutes of mowing time, I happened to look at the shutoff knob and it had partially moved to the closed position due to vibration. It was shutting off the fuel flow by itself.

The video that MParr sent you is a very real problem that even good shops miss. Anywhere there is and elbow or a valve in a fuel line is a potential for debris to collect. Grass clippings, bugs and even dust all collect in a fuel tank over years of use.

All fuel lines need to be blown clean with compressed air from time to time to minimize this problem.

 

[MParr]

I believe the fuel tank pickup line is going to be the issue. They collect debris over time and it is very subtle for it to gradually choke up and restrict fuel flow. When the mower shuts down, the "stuff" relaxes then allows fuel flow for a short time until it acts up again.

There are a very few machines that have a screen on the end of the pickup tube, but sediment will even get through the screen eventually.

The strangest fuel restriction I have seen was a Cub Cadet Z-Force that actually had a 90 degree elbow with a worn plastic shutoff valve. Right at about 15 minutes of mowing time, I happened to look at the shutoff knob and it had partially moved to the closed position due to vibration. It was shutting off the fuel flow by itself.

The video that MParr sent you is a very real problem that even good shops miss. Anywhere there is and elbow or a valve in a fuel line is a potential for debris to collect. Grass clippings, bugs and even dust all collect in a fuel tank over years of use.

All fuel lines need to be blown clean with compressed air from time to time to minimize this problem.

I'm leaning towards trash in the tank and deteriorating fuel lines.

 

[sgkent]

I just had a device that had been stored act that way. Blew out the lines and all was good. No idea what got into a sealed system but it did somehow.

 

[JP98]

Thanks for all the input, fellas! I guess while I'm already changing the fuel filter and fuel pump, I might as well blow out the lines too.

 

[MParr]

Thanks for all the input, fellas! I guess while I'm already changing the fuel filter and fuel pump, I might as well blow out the lines too.

You may want to remove the fuel tank and clean it out. It's better to get everything cleaned out than throw more parts at it.

 

[JP98]

You may want to remove the fuel tank and clean it out. It's better to get everything cleaned out than throw more parts at it.

I was trying to avoid doing that, but I know I really should do it. I looked inside the fuel tank, and it looked clean. I know.... I'm just being lazy. I really need to do it.
The fuel pump and filter are pretty cheap so I figured I should go ahead and do that as well. I have a spare shut off valve. Might as well install that too since it doesn't have one.