2021 John Deere has a Non vented, recirculating fuel system that may have a clogged return hose. Can it be bypassed or unclogged easily?

[rayikeo2]

My S240 Lawn Tractor mower gas system was keeping the mower from running longer than 5 minutes. I found the fuel hose from the filter to the fuel pump was clogged. I replaced that section, and now it is running but the return line from the carb to the fuel tank is also clogged. I can't blow through the line, but the mower is running now. Can the return line be bypassed, or will I have to run a new line from the carb to the gas tank? The fuel cap is unvented.
Maybe the return line is ok, there is a pressure vent somewhere in the system and it may be in the cap, I don't know exactly how this system works.

 

[sea2summit]

A gas mower with a carburetor has a return line? I've not heard of such a monster but fuel line is cheap, I'd just get a new piece and replace it.

 

[beenthere]

carb system system with return line ..

If plugged lines, I'd consider replacing lines and also pin-pointing source of dirt causing the plugging

 

[rayikeo2]

A gas mower with a carburetor has a return line? I've not heard of such a monster but fuel line is cheap, I'd just get a new piece and replace it.

The problem with this return line it goes under the body and into the tank at a hard to reach place without taking things apart, which I would rather not do. The new mowers now have this recirculating fuel system for emission control. It keeps fuel vaper from escaping into the air. Fuel caps have no vent hole. Not all the lower priced mowers have changed to this type of closed vent system.

 

[beenthere]

"..rather not do.."
What is the alternative?

 

[sea2summit]

The problem with this return line it goes under the body and into the tank at a hard to reach place without taking things apart, which I would rather not do. The new mowers now have this recirculating fuel system for emission control. It keeps fuel vaper from escaping into the air. Fuel caps have no vent hole. Not all the lower priced mowers have changed to this type of closed vent system.

Get a chunk of 1/4” all thread, about an inch and half should do. Stick half it in your new hose and put a hose clamp on it, put the other half in one end of the old hose and clamp it. Pull on the other end of the old hose.

 

[rayikeo2]

carb system system with return line ..

If plugged lines, I'd consider replacing lines and also pin-pointing source of dirt causing the plugging

My dealer said it was probably a bad fuel problem from using 10% ethanol fuel that may be old or contained contaminates.

 

[rayikeo2]

"..rather not do.."
What is the alternative?

I was hoping that it could be blown free or reamed with something that wouldn't damage it. Another thought, I need to learn more information about how this new system works.

 

[rayikeo2]

Get a chunk of 1/4” all thread, about an inch and half should do. Stick half it in your new hose and put a hose clamp on it, put the other half in one end of the old hose and clamp it. Pull on the other end of the old hose.

That sounds like a good idea, I may try that, after I get some new fuel line. Thanks.

 

[RandyT]

A gas mower with a carburetor has a return line? I've not heard of such a monster but fuel line is cheap, I'd just get a new piece and replace it.

All mowers after 2012 cannot bent directly to the atmosphere due to EPA regs. The line he is talking about is a vapor line and could either connect to the roll over valve in the top of the tank or connect to a charcoal canister similar to the coffee can on cars of the 70's. I have had a few come through the shop over the years due to clogging issues with the roll over valve due to people trying to squeeze the last drop of fuel into the tank resulting in bricking the valve.

Cannot be legally bypassed, but it also appears that JD doesn't offer a replacement of the valve itself which would require replacement of the fuel tank. This system operates very similar to the automotive evap systems but there is no purge valve. So when running the tank is actually under a small amount of vacuum but the fuel pump will overcome that vacuum and still operate, I have had a few mowers in the shop over the years that had the gravity flow tanks which I used to use the 40 micron filters on but starting having issues with fuel flow because of the vacuum with low tank volumes and had to switch to the 75 micron filters.

 

[tomplum]

It is really odd to have the fuel line aft the fuel filter clog. Was it clogged with old filter material? Bad line?
In regards to the vapor system, the line is small- but mouth pressure will find its way to the other end. the little orifice in the air box must be open obviously. Remember that tiny hole in the old fuel caps? That's all the volume of air that needs to pass to keep the tank flow going. Remember dipping the straw in milk or soda when you were a kid, and when you plugged the "vent" by holding the straw- the liquid wouldn't come out of the straw? There's your visual of how the system works. Except it doesn't spill all over your shirt when you take your finger off...

 

[Tinhack]

Are you sure it's not a hose going to the EPA canister? That would be the "vent" for the tank. The canister is filled with charcoal to absorb gasoline vapors when parked. When running or using fuel, the vapor is drawn back into carb. Don't be poking or blowing in that line if it is a canister system. They can get VERY expensive to replace and will cause your engine to run like crap if damaged.

 

[rayikeo2]

I am still having a problem with air coming into the bottom of the fuel filter and when it gulps a big bubble, the motor shuts down. I will try the better fuel filter (75 micron) and see if there is any change. Where is the best place to find that filter?

 

[rayikeo2]

Why does an 85 micron filter work when a 40 micron won't?

 

[tomplum]

A working pulse pump can handle either. There's a bunch of things that are going left unsaid here. Like what had clogged the line. Did you install the fuel line complete? Air in you fuel filter is not abnormal. If you are drawing air in from poorly sealing line, cracked pick up tube and not fuel- that could be a problem.
It seems like you feel that there is a fuel delivery problem. To help find where , try the donor can approach. Take some new 1/4" fuel line and drop it into a container of fresh fuel- hooking the other end to the back of the fuel filter. Then run and see if stall is affected. A working pulse pump has no problem lifting fuel over 18".

 

[rayikeo2]

OK, I used a donor furl can and it will run without stalling, How do I replace the fuel pickup tube so I can eliminate that?

 

[Allan Keem]

In a typical fuel system of a lawn tractor, the return line serves an important function by allowing excess fuel from the carburetor to be returned to the fuel tank. This helps regulate fuel pressure and prevents flooding or overpressurization of the carburetor.
If the return line is clogged, it is advisable to address the issue rather than bypassing it. Running a new line from the carburetor to the fuel tank would be the ideal solution to ensure proper functioning of the fuel system.
Before replacing the line, you can try a few troubleshooting steps:
Verify the existence of a pressure vent: As you mentioned, the fuel cap may have a built-in pressure vent to regulate the fuel system's pressure. Check the cap for any signs of blockage or malfunction. Cleaning or replacing the fuel cap may alleviate the pressure issue.
Clearing the clog: Attempt to clear the clog in the return line by using compressed air or a small-diameter wire to gently dislodge any obstructions. Ensure that the line is completely free from blockages to allow proper fuel flow.
If these troubleshooting steps don't resolve the issue, it would be best to replace the clogged return line with a new one. Running a new line from the carburetor to the fuel tank will restore the proper functioning of the fuel system and prevent potential problems in the future.

 

[rayikeo2]

A working pulse pump can handle either. There's a bunch of things that are going left unsaid here. Like what had clogged the line. Did you install the fuel line complete? Air in you fuel filter is not abnormal. If you are drawing air in from poorly sealing line, cracked pick up tube and not fuel- that could be a problem.
It seems like you feel that there is a fuel delivery problem. To help find where , try the donor can approach. Take some new 1/4" fuel line and drop it into a container of fresh fuel- hooking the other end to the back of the fuel filter. Then run and see if stall is affected. A working pulse pump has no problem lifting fuel over 18".

In a typical fuel system of a lawn tractor, the return line serves an important function by allowing excess fuel from the carburetor to be returned to the fuel tank. This helps regulate fuel pressure and prevents flooding or overpressurization of the carburetor.
If the return line is clogged, it is advisable to address the issue rather than bypassing it. Running a new line from the carburetor to the fuel tank would be the ideal solution to ensure proper functioning of the fuel system.
Before replacing the line, you can try a few troubleshooting steps:
Verify the existence of a pressure vent: As you mentioned, the fuel cap may have a built-in pressure vent to regulate the fuel system's pressure. Check the cap for any signs of blockage or malfunction. Cleaning or replacing the fuel cap may alleviate the pressure issue.
Clearing the clog: Attempt to clear the clog in the return line by using compressed air or a small-diameter wire to gently dislodge any obstructions. Ensure that the line is completely free from blockages to allow proper fuel flow.
If these troubleshooting steps don't resolve the issue, it would be best to replace the clogged return line with a new one. Running a new line from the carburetor to the fuel tank will restore the proper functioning of the fuel system and prevent potential problems in the future.

Great News, With the information supplied with these two quotes I was able to fix my problem. I had to clean out and blow out my fuel lines from the carburetor to the gas tank and it was a success. My S240 started right up and I was able to mow my yard without any engine or fuel problems. Thanks to everyone for the help. I have been fighting this problem for more than 2 weeks.

 

[tomplum]

Glad you are fixed up. These things are quite frustrating. Hopefully it's a while before the pick up gets stopped up again, but at least you can get it going again.

To be clear to any that read this going forward, there isn't a fuel return line in these applications. It is simply a vent hose that attaches to the inlet elbow of the carb.

 

[Richard001]

In a typical fuel system of a lawn tractor, the return line serves an important function by allowing excess fuel from the carburetor to be returned to the fuel tank. This helps regulate fuel pressure and prevents flooding or overpressurization of the carburetor.
If the return line is clogged, it is advisable to address the issue rather than bypassing it. Running a new line from the carburetor to the fuel tank would be the ideal solution to ensure proper functioning of the fuel system.
Before replacing the line, you can try a few troubleshooting steps:
Verify the existence of a pressure vent: As you mentioned, the fuel cap may have a built-in pressure vent to regulate the fuel system's pressure. Check the cap for any signs of blockage or malfunction. Cleaning or replacing the fuel cap may alleviate the pressure issue.
Clearing the clog: Attempt to clear the clog in the return line by using compressed air or a small-diameter wire to gently dislodge any obstructions. Ensure that the line is completely free from blockages to allow proper fuel flow.
If these troubleshooting steps don't resolve the issue, it would be best to replace the clogged return line with a new one. Running a new line from the carburetor to the fuel tank will restore the proper functioning of the fuel system and prevent potential problems in the future.

Allen, welcome to TBN