John Deere L120 Mower Problem

MattFHamby · Jul 8, 2013

I had a problem with my mower, I have 300 hours on it, it is about 8 years old. It would run for about 1 hour and start acting like it was running out of gas. I thought it might be the fuel pump, changed that, changed the fuel filter, it kept doing that, I tried cleaning the fuel tank and run it, the fuel filter then was full of debris, it would shut off, I rotated the filter and it would run for a while, then shut off, i would turn the filter again and it would run for a while and shut off I continued this for a few times more until I finished my yard. I replaced the filter again and this time when it acted like it was starving of gas it shut off and would not start again - as a note, I didn't wait between restarting the mower the previous times, just long enough to tap and turn the filter. I talked with a repair tech. that suggested that I clean all of the gas lines. I pulled the carburetor off and the "body" to get to the gas tank, I cleaned all the gas lines and the tank, replaced the filter, took the carburetor to the tech and had him clean it for me. I got it back and assembled the mower and I was missing the throttle link and I noticed that the throttle cable was bent (mangled) - I ordered new ones and installed them. Prior to this I did run the mower (I wired the throttle to a position that felt about right, speed and sound), I run it for about an hour or so without any problems, I didn't do more because I didn't feel comfortable with my rigging. Anyway, once I got the parts in I installed them and could not get the throttle to work correctly, I have looked at the manual and could not see anything that was different than the way mine works. I can't figure out what is wrong, I didn't touch any of that linkage when I removed the carburetor - only the link that connected the actuator arm to the throttle on the carburetor. It seems like the mechanics work backwards, it looks to me like the "resting" position - the position that all of the springs pull to would be the lowest position of the throttle. I have included all the pictures I thought would be useful.

INDIANA ROWE · Jul 9, 2013

I have to ask... Can you clarify "rotating the filter" for me (and others here)? Is this an inline fuel filter? If so, then most have an arrow on them for the direction of the fuel.

MattFHamby · Jul 9, 2013

Sorry, by rotate I mean that I rolled it over so the debris in it was on top and not in the fuel in the filter. The fuel was never filling the filter more than just enough to be picked up by the fuel line on the pump side. And sorry to go into so much detail, but I'm not sure that the original problem has even gone away, I won't know that until I can get the issue with the throttle resolved. I am at a complete loss as to what is wrong, I have looked at the manual and everything, as best as I can tell, looks correct, however, when the throttle handle is move to slow, the rear piece that is linked to the throttle on the carburetor does not move. I was careful when I removed the carb to not mess with that, so putting it back in and hooking the link back in should have been OK, unless it was never set right to begin with which doesn't make sense either because it was running at the "correct" speed to begin with, the way it is right now I can't get it out od wide open which will blow up my engine!

Thanks for the reply, and any help would be much appreciated!

pacerron · Jul 9, 2013

The L120 I have has a 20 HP Briggs V-tec engine. The manual shows 2 other engines that were also used in that model.
Which engine is yours?
I'm sure you know about the vent clogging in the gas cap causing the engines to bog down and quit after a while depending on how much gas is in the tank....
I had a no power under load problem a couple weeks ago on mine which has 906 hours on it. I cleaned and gaped the plugs, although they looked good and were gaped correctly before I cleaned them, and blew out the filters. That didn't help.
I spent an hour or so reading all the attempts that failed by the TBN members.

The plugs, fuel filter, and air filters were original but looked good.
Never the less, I got a L120 maintenance kit that had new ones plus 2 qts. of oil and oil filter.
Changed them all out at once and the unit runs great with full power.

My point is, you can't really tell if the air filters, fuel filter, and plugs are good by the looks of them.
I was lucky to get 900 hours w/o any problems. John Deere recommends changing them all every year.
If you haven't changed them all, just do it. You can buy everything at auto parts stores except for the air filters
and save a few bucks but the time and gas wasted isn't worth it, IMO.

MattFHamby · Jul 9, 2013

It is the 20 HP v-tech b&g, I do the full tune-up at the beginning of every year. I also sharpen my own blades, and clean it regularly, I was also running 93 octane until I found out about what ethanol does to the engine, so I found a local gas station that sells the 89 octane in non-ethanol. I did find out about the has cap problem, I have not had a chance to check on that though. My problem at the moment is the throttle mechanism, something is just not right. Some pics of yours would be greatly appreciated!

I hope cleaning out the gas tank and fuel lines did the trick - I was surprised that there was any debris at all because before I take the cap off I blow it off then open it. I cleaned them by removing each end of both houses and blowing them out with the air compressor. They had a lot of crud in them, so I have now added a strainer cloth over my funnel to help catch anything from the gas can, etc...

pacerron · Jul 10, 2013

Do you have pictures of how you have the linkage hooked back up?
The throttle cable just goes in the hole in the circular rotating plate and the plate turns counterclockwise when the throttle is opened.
If your piece shown with the ruler is the governor linkage it looks bent. It just goes vertically between the 2 holes.

MattFHamby · Jul 10, 2013

Yeah, it had to be bent slightly to pass freely by the intake manifold. It was just hooked between the 2, but when you move the piece that rotates that is in front, the governor arm doesn't move. I can't figure how that is supposed to work, I did think that the link that is bent may be too short, why I showed it beside a tape measure, however if the gov. arm doesn't move, then it won't make any difference. It looks like resting position with the cable disconnected would be in the slow position.

tractorshopper · Jul 10, 2013

Had same problem with my L118. Did a ton of work like you. Nothing fixed it. Found out that the gas cap tiny breather hole was clogged (it should be in the center of the gas cap and mine was dusted over so I couldn't even see it was supposed to be there). Unclogged it with a small nail and never had another problem.

pacerron · Jul 10, 2013

MattFHamby said:
Yeah, it had to be bent slightly to pass freely by the intake manifold. It was just hooked between the 2, but when you move the piece that rotates that is in front, the governor arm doesn't move. I can't figure how that is supposed to work, I did think that the link that is bent may be too short, why I showed it beside a tape measure, however if the gov. arm doesn't move, then it won't make any difference. It looks like resting position with the cable disconnected would be in the slow position.

My governor arm doesn't move either when the throttle is moved from full closed to full open with the engine not running.
Usually one end of a governor arm is controlled by a spring that has more or less tension due to the rotation of the engine shroud fan. If the engine slows a little or sputters the mechanism wiggles the throttle plate a little to maintain a smooth idle.
I just got back home from being gone most of the day.
If you want pictures, it looks like I will have to take the hood totally off to get a good view. Does it just pop off the hinge pins that have the spring hooks over them or do the bolts through the metal bracket into the front bottom of the inside of the hood have to be removed?

MattFHamby · Jul 10, 2013

It comes off by pulling the springs back and out, then the whole good slides off. But that's OK, I stopped by Home Depot and found one that was nearly identical, I see that all I had to do was hook it up, evidently when the engine starts the governor arm raises and allows it all to work correctly. I just ***-you-me-d that it should actuate with the engine off. I hooked it all up and wouldn't you know it, it works! By the way, I checked the gas cap and the vent was clogged, I cleaned it and mowed through a tank and a half of gas with no problems! So, it looks like one of the many things I did fixed it! Probably the gas cap vent!