4020 leans out when hot, vapor lock?

mrjata

New User
Got a 4020 gas, acting up a bit. When I have been running for an hour or so in the hay field at temp, it starts to lean out, so I tug a little on the choke, it runs fine, then after a while it almost dies, and I limp back to the house with the choke fully pulled. Already flushed the tank, carb is clean (Zenith). The fuel line seems very close to the block and was very hot to the touch, carb seemed warm too, warmer than a coffee cup. Is it a fuel delivery issue or a fuel metering issue. Been several years since I put a lift pump on it. I am thinking of pulling the fuel line away from the block as far as I can, maybe insulate it with left over fiberglass header wrap.

I am open to ideas. Tractor runs great when cool

Temp outside today was 85, no wind
 
Got a 4020 gas, acting up a bit. When I have been running for an hour or so in the hay field at temp, it starts to lean out, so I tug a little on the choke, it runs fine, then after a while it almost dies, and I limp back to the house with the choke fully pulled. Already flushed the tank, carb is clean (Zenith). The fuel line seems very close to the block and was very hot to the touch, carb seemed warm too, warmer than a coffee cup. Is it a fuel delivery issue or a fuel metering issue. Been several years since I put a lift pump on it. I am thinking of pulling the fuel line away from the block as far as I can, maybe insulate it with left over fiberglass header wrap.

I am open to ideas. Tractor runs great when cool

Temp outside today was 85, no wind
Your on the wright trak with insulating fuel line next is the manifold heat exchanger set for warm weather and the best thing for them is an electric fuel pump.
 
Got a 4020 gas, acting up a bit. When I have been running for an hour or so in the hay field at temp, it starts to lean out, so I tug a little on the choke, it runs fine, then after a while it almost dies, and I limp back to the house with the choke fully pulled. Already flushed the tank, carb is clean (Zenith). The fuel line seems very close to the block and was very hot to the touch, carb seemed warm too, warmer than a coffee cup. Is it a fuel delivery issue or a fuel metering issue. Been several years since I put a lift pump on it. I am thinking of pulling the fuel line away from the block as far as I can, maybe insulate it with left over fiberglass header wrap.

I am open to ideas. Tractor runs great when cool

Temp outside today was 85, no wind
Vapor lock could be a symptom of a failing fuel lift pump that cannot maintain adequate fuel pressure. With front mounted fuel tanks fuel is gravity fed when the tank is full. As the fuel level drops below the carburetor the lift pump becomes important. Needing full choke to run is pretty drastic.
 
The tank is in front of the radiator. I would approximate the tank outlet is and inch or two above the crankshaft centerline.
To OP mrj..
YT post with info In this YT post from the past it shows a way monitor the level of the fuel in your carb bowl as it is running. To keep the dust and debris out of the tube tape a piece of clothes over it. FYI, the photos at the end of the post clearer. Might be able to find a red bead pervious to gasoline to that will show the level better.
 
Got a 4020 gas, acting up a bit. When I have been running for an hour or so in the hay field at temp, it starts to lean out, so I tug a little on the choke, it runs fine, then after a while it almost dies, and I limp back to the house with the choke fully pulled. Already flushed the tank, carb is clean (Zenith). The fuel line seems very close to the block and was very hot to the touch, carb seemed warm too, warmer than a coffee cup. Is it a fuel delivery issue or a fuel metering issue. Been several years since I put a lift pump on it. I am thinking of pulling the fuel line away from the block as far as I can, maybe insulate it with left over fiberglass header wrap.

I am open to ideas. Tractor runs great when cool

Temp outside today was 85, no wind
Checking fuel pressure used to be a common thing and anyone who did much mechanical work had a low pressure test gauge to "T" into the fuel line ahead of the carburetor.

Adequate pressure is protective against "vapor lock".

John Deere SM-2039 specifies the fuel pressure at 3.5 to 4.5 psi @1900 RPM's.
 
First of all, if you're using E85, you're at an immediate disadvantage. It will work if you keep EVERYTHING as cool as possible. I use the gas they give us, which is E85, in the few gas tractors we have left but I ensure that the engine temperature is as cool as possible and that the transfer pump is working properly along with a full-flow situation from the tank. I doubt that it's a carburetor problem.
 
I am going to put a lift pump on and insulate the fuel line, both. This has happened before, same symptoms. And yes, once it was when the tank was on the last 1/4 of volume. This time it is 3/5 tank level but the pump can also restrict fuel flow just from gravity so it could be defeating the purpose too. Am I way off here? I know higher fuel pressure would help eliminate or minimize the chance of vapor locking.

Keep the ideas coming, thanks
 
First of all, if you're using E85, you're at an immediate disadvantage. It will work if you keep EVERYTHING as cool as possible. I use the gas they give us, which is E85, in the few gas tractors we have left but I ensure that the engine temperature is as cool as possible and that the transfer pump is working properly along with a full-flow situation from the tank. I doubt that it's a carburetor problem.
Don't you mean E10 or E15? E85 is the yellow pump nozzles around me.
 
Just plain pump gas, going to check a fuel sample today, maybe get the fuel line moved. Going to talk to a JD tech tomorrow
 
Haven't checked fuel pressure, but if it was low it wouldn't run much at all, even with the choke pulled. All things are pointing to percolation or vapor lock. Might get the lift pump to be safe, not expensive at all. But All states ag shows 2. wonder what the difference is?? One looks like two cylindrical pumps the other looks like a traditional fuel pump more of one large dome, much like the glass bowls that used to be there. Any thoughts on those??
 
Gas flow vapor lock was a common problem on the 4010 and 4020 gas tractors. You do have the manifold heat valve block set for summer use, the cold position? Do pull the gas line to the carburetor away from the block and wrap in aluminum foil. Gas cap, may not be venting? May loosen and run to see if any difference? If not, then may be the fuel pump.
 
Gas flow vapor lock was a common problem on the 4010 and 4020 gas tractors. You do have the manifold heat valve block set for summer use, the cold position? Do pull the gas line to the carburetor away from the block and wrap in aluminum foil. Gas cap, may not be venting? May loosen and run to see if any difference? If not, then may be the fuel pump.
Agree on the manifold heat blocks for winter. Change to summer setting. Look in your OM.
 
Haven't checked fuel pressure, but if it was low it wouldn't run much at all, even with the choke pulled. All things are pointing to percolation or vapor lock. Might get the lift pump to be safe, not expensive at all. But All states ag shows 2. wonder what the difference is?? One looks like two cylindrical pumps the other looks like a traditional fuel pump more of one large dome, much like the glass bowls that used to be there. Any thoughts on those??
I'll say it one more time, pressurized fuel is LESS likely to boil/vapor lock, so it's worth verifying that the pump is making proper pressure.

As to the new ones, AFAIK they all work the same.
 
I am going to put a lift pump on and insulate the fuel line, both. This has happened before, same symptoms. And yes, once it was when the tank was on the last 1/4 of volume. This time it is 3/5 tank level but the pump can also restrict fuel flow just from gravity so it could be defeating the purpose too. Am I way off here? I know higher fuel pressure would help eliminate or minimize the chance of vapor locking.

Keep the ideas coming, thanks
well u are getting idea's but not following up on them. checking fuel pump pressure was standard procedure years back on tune ups.
 
Difference in the 2 pumps might be which way
the outlet & inlet fittings are arranged on the
pump. Last pump I put on the 4020 I had to get
another one because the fittings were diagonally
opposite. The dealer carried both pumps.

Brothers 4010 with marvel shebler carb has to have
the choke out 1/8" to run right. Never thought too
much of MS carbs.
Jim
 

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