Kubota d640 losing fuel prime

[Sooty.Mangabey]

I have a D640 that will immediately lose its fuel prime after being shut off, no visable fuel leaks on any hard lines. I can bleed the lines and start it and it will run fine, but if I shut it off and try to restart will just crank. Lift pump moves fuel fine I checked with the 2 bleeder screws

I noticed that one injector nozzle is leaking air from around the threads were it mounts into the block, I only noticed because fuel pooled up around it from bleeding the lines. I tried to tighten it up more but it is fully seated and i don't want to do anything to the threads.

should I look into getting new nozzles? The motor never had a problem until recently when the injection pump o rings were replaced.

 

[Workerbee]

Likely need to go thru the pump again and make sure the o-rings are ok. And do be sure everything is squeaky clean. If a problem shows up immediately after doing something , there’s a good chance they’re related.

 

[Sooty.Mangabey]

pulled all of the plungers again and they are all fine, It ran great until I replaced the o rings on the delivery valves. Should have just left it alone but it was leaking diesel bad. I'm replacing all the rubber hoses on the overflow side and will go from there.

 

[thepumpguysc]

Did u use OEM orings.??
Did u replace the copper dv gaskets.??
If no, theres your problem. Did u TORQUE the dv holders.??
Using any old oring that "looks like" the right ones doesnt cut it..
& the dv gaskets are a "crush" seal.. if u reused them.. well, u get the idea.

 

[Sooty.Mangabey]

Did u use OEM orings.??
Did u replace the copper dv gaskets.??
If no, theres your problem. Did u TORQUE the dv holders.??
Using any old oring that "looks like" the right ones doesnt cut it..
& the dv gaskets are a "crush" seal.. if u reused them.. well, u get the idea.

Im sorry I should have been more clear I didnt replace the oring on the delivery valve itself but the 2 rings on the plunger it goes into. The parts breakdown book calls it the Sleeve flange. I removed the 2 torx safety heads amd pulled the whole assembly out and i did use the correct o rings. Though one of the delivery valve holders did start turning when i was loosening the lines so I will replace the washer on it next.

Thank you for you help.

 

[littleorangetractor]

I had this problem with my B6000. It turned out to be a very small leak in one of the pipe connections on top of the injector pump. I noticed a small amount of fuel was seeping out there. After bleeding the fuel system, the engine would start just fine. Next morning I had the same problem. It turned out where the fuel was leaking out when running, with the engine stopped, air would leak in and the pump lost its prime again.
The leaking connection was taken apart, cleaned and reassembled with a small amount of Permatex Pneumatic/Hydraulic thread sealant. Haven’t had a loss of prime since then.

 

[North Idaho Wolfman]

I'm going to say it's very possible that your going to need to have the injection pump professionally rebuilt!

That still is not going to fix the issue, it's more likely a supply issue than a delivery issue.

If it was a delivery issue it should only affect one cylinder not all three.

 

[Sooty.Mangabey]

I'm going to say it's very possible that your going to need to have the injection pump professionally rebuilt!

That still is not going to fix the issue, it's more likely a supply issue than a delivery issue.

If it was a delivery issue it should only affect one cylinder not all three.

I went ahead and ordered a rebuilt injection pump from Grainfarmer, i also got new braided return lines in the mail and if need be I will get new injectors. All i know is it ran great until I replaced the o rings, it just leaked fuel something terrible. I do think that the pump was weak because to me it seemed like fuel was not coming out with the pressure i thought it should have when I bled the injectors. The motor does have 3500 hours on it so im sure it was weak to begin with.

I will update when i get the new pump on.

 

[North Idaho Wolfman]

I went ahead and ordered a rebuilt injection pump from Grainfarmer, i also got new braided return lines in the mail and if need be I will get new injectors. All i know is it ran great until I replaced the o rings, it just leaked fuel something terrible. I do think that the pump was weak because to me it seemed like fuel was not coming out with the pressure i thought it should have when I bled the injectors. The motor does have 3500 hours on it so im sure it was weak to begin with.

I will update when i get the new pump on.

I think you made the right choice!

This is no slight on you at all, I see it so many times when people pull the delivery valves off it messes the pump up, the top plates are adjustments for the individual fuel delivery.

Fuel injection pumps without restriction don't really put out much pressure, or flow, it's only when you reduce it down at the injector tip does it reach high pressure.
With 3500 hours I personally would just change the injectors, and glow plugs as they more than likely are both, if not anything else severely underperforming.

Your on a good path!

 

[Sooty.Mangabey]

I'm going to say it's very possible that your going to need to have the injection pump professionally rebuilt!

That still is not going to fix the issue, it's more likely a supply issue than a delivery issue.

If it was a delivery issue it should only affect one cylinder not all three.

New Pump is on and its running great, going to start a new thread on my restoration.

 

[North Idaho Wolfman]

New Pump is on and its running great, going to start a new thread on my restoration.

Excellent to hear!