John Deere 4020 Gas Carb Issue

[Dairy Feeder]

I recently acquired a John Deere 4020 Gas PowerShift and I have installed a Brand New Zenith Carburetor that's pours fuel out the throat of the Carb after a few seconds of Cranking, the tractor tried to start twice but then nothing. When I pull the plugs only 1 plug has gas on it. I have good spark, new fuel pump etc. I'm thinking the float isn't shutting off the fuel?? The Marvel Carb that was on it did the exact same thing so I'm a bit perplexed and would appreciate any help.

 

[wore out]

I recently acquired a John Deere 4020 Gas PowerShift and I have installed a Brand New Zenith Carburetor that's pours fuel out the throat of the Carb after a few seconds of Cranking, the tractor tried to start twice but then nothing. When I pull the plugs only 1 plug has gas on it. I have good spark, new fuel pump etc. I'm thinking the float isn't shutting off the fuel?? The Marvel Carb that was on it did the exact same thing so I'm a bit perplexed and would appreciate any help.

Are you choking it while cranking?

Did you verify that the air intake system, including the air cleaner and all piping is "open" and free-flowing?

Is the tractor in freezing temps, if so, and it has an oil bath air cleaner, frozen water in the oil cup will restrict air flow.

You could disconnect the air intake tube from the carb and see if it will start (and not flood) then.

But be aware that a "backfire" will puke flame out the air horn and take the appropriate precautions!

Photo is of my 4020 "Ingrid" after blowing snow at 20 below!

 

[Dairy Feeder]

Yes, I'm choking it and the choke is closing fully, I have disconnected air intake tube and fuel still comes out. It was 55 degrees the day I was working on it.

 

[M-MAN]

Turn the switch to on and then check for gas dripping. If it does the needle and seat or the float is at fault. If it only does it while cranking you have another problem.

 

[Dairy Feeder]

It only does it while Cranking

 

[wore out]

Turn the switch to on and then check for gas dripping. If it does the needle and seat or the float is at fault. If it only does it while cranking you have another problem.

It has a mechanical fuel pump, so why would "turning the switch on" have any effect on whether or not the carb would "run over"?

If it doesn't "run over" while cranking WITHOUT the choke being pulled the float, needle and seat are fine.

 

[used red MN]

Don’t forget you also need spark to make it run! If you think it is not getting enough gas pull a couple plugs and poor a tablespoon of gas in them. If it fires immediately then gas delivery is probably where you need to continue looking for problems.

 

[Fixingfarmer]

1. New carb mounting gasket? Why some manufacturers make you order this separate especially on a zenith with all those bolts on the back side I will never know.
2. Condition of the intake manifold gasket?
3. I was looking for a carb accelerator pump the other day for the 3020 that was in the shop and I did see that there is a kit for electric fuel shutoff I’m assuming yours doesn’t have it this one didn’t either. If it did switch on might have some effect. The flooding a bit at the start I believe to be a symptom more than the problem itself. While it’s not great the tractor should start and when it fails there’s fuel in that intake that will run back down. Air delivery problem because of a plugged filter or intake restriction on that side will cause this also but it sounds like you have the pipe off carburetor so that should eliminate that. Especially with a new carb I’d hesitate to say it’s a float problem since it only does it while cranking just like wore out said.

 

[dieselade]

push choke in most of the way after two seconds of cranking, or maybe sooner, just a suggestion,

 

[M-MAN]

It has a mechanical fuel pump, so why would "turning the switch on" have any effect on whether or not the carb would "run over"?

If it doesn't "run over" while cranking WITHOUT the choke being pulled the float, needle and seat are fine.

Just a generalization to cover pert near anything whether electric fuel pump, carb solenoid or purely mechanical.

 

[MSD]

Pull the throttle all the way to idle position and no choke. It will draw fuel off the idle circuit and not flood. Also take carb off and while holding it in the position it would be in if mounted blow into the fuel inlet and it should let you blow air in. Turn it over and try again. If you can still blow in your needle and seat are not working properly.