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John Deere 425 Fuel Pump Options


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#1 Tractorbuds OFFLINE  

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Posted February 02, 2013 - 02:51 PM

Hi there. I just acquired a 425 fixer upper with a bad fuel pump. I'm wondering if anyone has just convert this tractor back to a basic vacuum operated fuel pump like you find on most garden tractors with under seat tanks? Let me know...cheers



#2 olcowhand ONLINE  

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Posted February 02, 2013 - 03:20 PM

I am not at all familiar with V twins, especially Kawa engines, but if they are like I figure they are, one piston is up, while the other is down, so there will be no pulse in the crankcase to power a vacuum fuel pump.  They work on singles, and on most flat twins where both pistons work at the same stroke, thus creating a change of block pressure between strokes.



#3 Tractorbuds OFFLINE  

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Posted February 02, 2013 - 03:52 PM

I am not at all familiar with V twins, especially Kawa engines, but if they are like I figure they are, one piston is up, while the other is down, so there will be no pulse in the crankcase to power a vacuum fuel pump.  They work on singles, and on most flat twins where both pistons work at the same stroke, thus creating a change of block pressure between strokes.

Pretty much all vtwins utilize a vacuum style pump even though they according to how you described it. B&S tend to pull the 'pulse' from inside the valve cover area whereas Kohlers pull from a part that comes right out of the upper crankcase.



#4 JDBrian OFFLINE  

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Posted February 02, 2013 - 04:37 PM

This may help. It is from the 425 tech manual. It describes the basic fuel system.

 

 

CARBURETED ENGINE FUEL AND AIR SYSTEM OPERATION—425

Function:

The fuel system supplies pressurized fuel to the carburetor for combustion. The air intake system filters air needed for combustion.

System Operation:

An electric fuel pump mounted inside the fuel tank provides pressurized fuel to the carburetor. The fuel pump uses the fuel for lubrication and cooling. The fuel pump draws fuel through the fuel pump filter. Low pressure fuel from the fuel pump flows through the fuel shut-off valve and in-line fuel filter to the carburetor. Fuel pressure is maintained at the carburetor inlet needle until the float allows more fuel in the bowl. The fuel tank relief/check valve prevents gas fumes from escaping into the air for emission control. When the fuel tank starts to create a vacuum, the check valve opens and allows air into the tank, but closes for air trying to escape from the tank. The tank will pressurize up to 3 kPa (0.4 psi) before the relief valve opens and allows the air pressure out. The fuel tank cap is NOT vented (carburetor vent solenoid only).






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