Outdoor Power Equipment and Small Engines - John Deere L120 Mower problem

Hi - I am having a problem with the subject mower. After mowing for about 20 minutes, the thing just dies. It seems like it is running out of fuel, but the fuel tank is full. Sometimes, if I put the choke on, it will start and keep running. It almost seemed like the fuel pump was shot. Another clue was that the fuel filter had air in it and not much fuel during this 'episode'.

I thought that the fuel pump might have been the issue, so I put a new one on. I also replaced the filter. The last time I mowed, I still had the same problem though.

The fuel pump is a diaphram pump (I think) and it works off of vacuum from the engine. It is possible that I lose vacuum after the engine heats up, but I don't know how to check that.
I am not even sure I am on the right track.

Any help would be appreciated here. I have been diddling around with this mower for a while and can't seem to figure it out. These things are so basic, however John Deere seemed to have gone nuts with putting interlocks and 'cya' stuff all over this mower. What's next - rubber blades?

Try loosening the fuel cap next time it dies. The problem sounds like a plugged vent in the fuel cap. This seems to be more common with rear mounted fuel tanks.
The more fuel in the tank, the more the problem will persist.
If this solves it you may be able to clean out the vent in the cap with compressed air.
I think JD is pretty proud of those cheap fuel caps.

Another thing you might have a look at is the fuel line coming from the tank. I have seen these have some fiber plug in the fuel line right at the tank nipple. Looks like the filter out of a cigarrette stuffed into the fuel line. I don't know what the intent was here, or if it's still done, but it causes this problem.

Imagine how long it took me to learn about that little tidbit...LOL!

Thanks for the tip - I will check the 'plugged' line and the vent.

I did put compressed air in the tank to see if the line from the tank was clogged. The strange thing is that when I took off the fuel line from the fuel filter, there was no gas coming from the tank. As soon as I put some compressed air in the tank, the fuel started to run freely. Unfortunately, that only temporarily fixed the problem.

Thanks again - I will let you know how I make out.

What engine do you have?
I dont think fuel should readily flow to the filter, if equiped with a fuel pump. Being able to force fuel through the line by pressurizing the tank I would think verify the line is prolly not plugged.

When I ran across this problem on the mower with the plugged line, gas would run out the fuel line, but slowly. Compressed air made it come out quickly. The problem was, gas wouldn't flow fast enough to keep the carb full, so the mower would run for awhile until the fuel in the line ran out and the restriction slowed the flow enough that the carb bagan to gradually starve for gas until it died. You could let it sit for awhile, and it would start back up and run off the fuel in the line again.

Cheese was that the same model? The fuel pickup on the L120 shows to come out the top of the tank...?

http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.HomePageServlet_Alt

Cheese describes exactly what is happening with this mower.

Cheese - how do I remove that 'fiber filter' in the fuel line? the tank is underneath the seat and is surrounded by the mower chassis. Do I have to take everything apart or is there an easier way to get at the fuel line pickup in the tank.

The L120 fuel line pickup does come out of the top of the tank. I would have expected a 'siphon' action when I disconnected the 'main' fuel filter, but fuel does not run out when this happens. It's very strange.
I am going to check it this weekend as I didn't have time this week and thankfully, the grass is not growing that fast this time of year!

I have done one similar and the tank required removal. It will come out with just a bit or contorsionist. The illustrated parts list does not show but I think there are 4 or 6 bolts that secure the tank. With the fuel lines removed and the tank drained, it should come out from the bottom. The fuel pickup is held in with a grommet.
The one I did had all of the fuel line cracking and brittle from the tank to the carb. The tank also had similar debris in it.

Well - I think I finally fixed this problem (with the help of this forum of course). The fuel cap vent hole was plugged with a white-ish looking substance. I took the cap apart and cleaned it up. Now the mower runs fine without starving for fuel.

I must say that I've never run across this problem before. Thanks for the tip.