ZG227 Fuel Pump

rickyinman

New member

Equipment
Kubota ZG227
Mar 25, 2022
1
0
1
Tennessee
I have determined my electric fuel pump needs to be replaced. The OEM fuel pump is $225 and an aftermarket fuel pump is $25. The only difference is the OEM pump has an extra wire. I have searched for 2 days and I haven't found any information about the extra wire. I called the Kubota dealership and they "thought" the extra wire allowed the pump to continue for a short time after the key is turned off.

Do any of you know the purpose of the extra wire?

A mechanic friend of mine suggested buying the aftermarket pump and leaving the extra wire disconnected (just using the positive and negative connections). Have any of you used an aftermarket pump?
 

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
5,444
2,137
113
Mid, South, USA
A little of my experience.

The OEM pump is tasked to PULL fuel from the fuel tank, which is mounted lower than the pump. Then it forces fuel through some lines, filter, bowl, valve, which are lower than the engine, then back UP to the carburetor. It's a huge task for such a small pump! MOST of the chinese aftermarket pumps will not pull fuel that well. I have plenty of experience with this. IOW, a certain 'friend' bought an airboat, and asked me to 'put it together'--it was recovered off of the bottom of the river. Yay me. Anyway, 454 GM engine. OE had a mechanical pump, he wanted electric for some reason. Every electric pump I tried wouldn't pull fuel up high enough to maintain fuel pressure at rated engine speed (about 5200 rpm). In fact, none of the pumps I used would even feed it at half that. Your Kubota is similar, but the pump doesn't make nearly the volume of fuel as what I was using. And yes I've both tried and had to repair ZG2xx series that used (or attempted to use) aftermarket $40 fuel pumps. They just do not work that well.

Also the OEM pump has a pressure cut built into it, so when fuel pressure rises to a predetermined pressure, the pump shuts off which helps prolong the life of the pump. It's also a bit of a safety feature in that if you rolled it on it's lid the pump would shut off and not keep pouring fuel into a possible fire situation.

The wiring is such that one is ground, another is keyed, and another goes to a relay that turns the pump on with engine rotation. Look at your wiring diagram-you'll see what I mean.
 
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Dave_eng

Well-known member
Lifetime Member

Equipment
M7040, Nuffield 465
Oct 6, 2012
5,257
1,042
113
Williamstown Ontario Canada
There is a critical pump parameter that is rarely provided when smaller pumps are involved but it can explain the lack of performance Lugbolt is outlining with the cheap pumps called upon to lift fluid into the pump inlet.
What is NPSH (Net Positive Suction Head) and Why Does it Matter?


The Net Positive Suction Head (NPSH) margin is a crucial factor that is commonly overlooked while selecting a pump. It is the difference between the NPSH available (NPSHa) at the pump’s inlet and the NPSH required (NPSHr) by the pump to operate without cavitation. Cavitation is the formation of bubbles at the pump inlet, followed by their sudden collapse, which can cause permanent damage. The NPSH margin value must be positive to avoid cavitation.


How does NPSH relate to Pump Operation?
Pumps work by creating a pressure differential between the inlet and the outlet—the high pressure at the inlet causes fluid to flow towards the low pressure at the outlet. As the fluid flows through the pump, it experiences steadily decreasing pressure along the flow path. If the pressure at the inlet falls below the vapor pressure of the fluid, bubbles will form at the inlet.
These bubbles collapse rapidly inside the pump as they move towards the outlet. This cavitation causes the pump to operate noisily, making it sound like something like gravel in a concrete mixer. The bubbles in the fluid also reduce the capacity of the pump.

Dave
 

whitetiger

Moderator
Staff member

Equipment
Kubota tech..BX2370, RCK60, B7100HST, RTV900 w plow, Ford 1100 FWA
Nov 20, 2011
3,175
1,597
113
Kansas City, KS
I have determined my electric fuel pump needs to be replaced. The OEM fuel pump is $225 and an aftermarket fuel pump is $25. The only difference is the OEM pump has an extra wire. I have searched for 2 days and I haven't found any information about the extra wire. I called the Kubota dealership and they "thought" the extra wire allowed the pump to continue for a short time after the key is turned off.

Do any of you know the purpose of the extra wire?

A mechanic friend of mine suggested buying the aftermarket pump and leaving the extra wire disconnected (just using the positive and negative connections). Have any of you used an aftermarket pump?
Why does your OEM pump need to be replaced?