Kubota d722 injection pump not pumping

Nutmeg

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Kubota D722
Mar 10, 2023
35
1
8
Pa
I just recently bought a d722 and port 1 and 3 are pumping fuel. Center port is not pumping. I replaced the plunger and barrel but it still does not pump. Any ideas? I'm really confused.
 

North Idaho Wolfman

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PLEASE... It's not KABOTA, IT'S KUBOTA
I've changed the title to reflect such change.
Change your profile too! ;)
 

Nutmeg

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Kubota D722
Mar 10, 2023
35
1
8
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Which direction does the center plunger need to be installed? I have the groove that goes straight up and down on the side facing away from the fuel return outlet. Just want to be sure I have it installed correctly
 

kubotafreak

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They can be installed 180 out. Usually the indications are the engine goes full throttle at startup. This may not always be the case though. If the cam lifter is fine the rack slide - plunger would be the next point to inspect.
 

Nutmeg

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Equipment
Kubota D722
Mar 10, 2023
35
1
8
Pa
They can be installed 180 out. Usually the indications are the engine goes full throttle at startup. This may not always be the case though. If the cam lifter is fine the rack slide - plunger would be the next point to inspect.
Brand new Bosch plunger
 

Nutmeg

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Kubota D722
Mar 10, 2023
35
1
8
Pa
*Update* so we finally got it to pump! It was air bound. But we have the return going straight to the fuel can. Doesn't the return need to be restricted like when it is going from each injector to the tank, so it can build a little bit of pressure in the injection pump to spray out of the injector? How does the return work?
 

kubotafreak

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GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Sep 20, 2018
1,012
366
83
Arkansas, US
*Update* so we finally got it to pump! It was air bound. But we have the return going straight to the fuel can. Doesn't the return need to be restricted like when it is going from each injector to the tank, so it can build a little bit of pressure in the injection pump to spray out of the injector? How does the return work?
Return is strait to tank on the older models. The newer ones introduce a check valve to prevent backflow(air). The return ideally does not have much flow. It is the fuel blow by past the plunger-bore. So less is better/less component wear.
 

Nutmeg

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Equipment
Kubota D722
Mar 10, 2023
35
1
8
Pa
Return is strait to tank on the older models. The newer ones introduce a check valve to prevent backflow(air). The return ideally does not have much flow. It is the fuel blow by past the plunger-bore. So less is better/less component wear.
Oh ok! Yea, this on has the check valve. And when I clamped the return hose shut a little, it sprayed out the ports better. (The return line is not on the injectors due to the injectors not installed currently) the valves are leaking currently so we will be doing a valve job. But we used a tiny bit of ether and it ran on 3 cylinders. But compression is too low on the 3rd cylinder to run on fuel. We hate using ether but we wanted to be sure it'll run before we but anything else for it. Thanks for the replies!! Ordering a over haul gasket kit for it and will relap the valves and hope it runs on all 3 without ether!
 

North Idaho Wolfman

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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
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Sandpoint, ID
Oh ok! Yea, this on has the check valve. And when I clamped the return hose shut a little, it sprayed out the ports better. (The return line is not on the injectors due to the injectors not installed currently) the valves are leaking currently so we will be doing a valve job. But we used a tiny bit of ether and it ran on 3 cylinders. But compression is too low on the 3rd cylinder to run on fuel. We hate using ether but we wanted to be sure it'll run before we but anything else for it. Thanks for the replies!! Ordering a over haul gasket kit for it and will relap the valves and hope it runs on all 3 without ether!
After ether you should order a full rebuild kit and be prepared to buy some rods too.

If you have the head off, check the height of all the cylinders if any do not come up to full height, it's bent the rod, and will need to be replaced, very common in these little engines with any ether use.
 

Nutmeg

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Equipment
Kubota D722
Mar 10, 2023
35
1
8
Pa
After ether you should order a full rebuild kit and be prepared to buy some rods too.

If you have the head off, check the height of all the cylinders if any do not come up to full height, it's bent the rod, and will need to be replaced, very common in these little engines with any ether use.
I was told the engine only has 1400 hrs on it. The pistons and everything's fine. Just the valves leaking
 

kubotafreak

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GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Sep 20, 2018
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83
Arkansas, US
The piston ring lands crack very easily. If they measure height wise and a cyl is low compression, the ring lands are prob cracked.
 

North Idaho Wolfman

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Jun 9, 2013
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Sandpoint, ID
I was told the engine only has 1400 hrs on it. The pistons and everything's fine. Just the valves leaking
These engines very rarely have valve issues.
Almost always when they have compression issues, it's piston, liner, or rings causing the loss of compression.
 

Nutmeg

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Equipment
Kubota D722
Mar 10, 2023
35
1
8
Pa
These engines very rarely have valve issues.
Almost always when they have compression issues, it's piston, liner, or rings causing the loss of compression.
We did a leak down test on it and nothing came out of the crank. Only came out the the exhaust on one cylinder and intake on another cylinder and the valves were shut all the way.
 

Nutmeg

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Equipment
Kubota D722
Mar 10, 2023
35
1
8
Pa
May have been fine before the ether. :confused:
We didn't give it much ether. Just enough to hear it run on cylinder number 3. Once we heard it run on all 3, we stopped and decided to do a valve job. Nothing happened to the rings or anything else. The ether was only coming out in drops, literally. The valves were leaking when we first tried starting it, without ether. We hate using it but we did not want to buy anything else for it until we heard it run on all 3.