kubota D722 issue

[alfapillar]

Hi Fellas ,

I have an issue on a Kubota D722 engine, fitted on a Kaeser air compressor.

the engine have electric feeding pump.

Fuel route is : tank - water separator - pre-filter - electric feeding pump - fuel filter - injection pump - injector.

the problem I have is : when connecting the electric feeding pump straight to the injection pump, the engine runs great ! but when we go through the fuel filter, the engine will run for a short time than dies, the fuel filter at that moment if removed is almost empty.

I thought about the filter housing, so replace it from another unit, and still the same, I used another pre-filter between the electric feeding pump and the injection pump, and engine will die ...

have changed hoses.

Any thought ?

Thanks mates.

 

[Russell King]

Look closely at the filter housing where the fuel enters the housing.

There is probably something clogging it up. There is probably some sort of screen that is plugged up (on both housings)

 

[alfapillar]

Look closely at the filter housing where the fuel enters the housing.

There is probably something clogging it up. There is probably some sort of screen that is plugged up (on both housings)

Thanks for the advice, have checked the housing, used air to be sure it's clean, still have the same problem even with two different housings.

 

[Russell King]

Then it may be the lift pump?

Fill the tank up completely and see if it runs. Or rig up some bottle of fuel above the filter housing and see what happens with the filter housing and fuel when running

 

[alfapillar]

Then it may be the lift pump?

Fill the tank up completely and see if it runs. Or rig up some bottle of fuel above the filter housing and see what happens with the filter housing and fuel when running

Lift pump replaced with a new one that have on stock.

Have tried with disconnecting the shutt off solenoid, as there is safety switches for oil pressure / engine temp / hydraulic oil temp : engine will dies

Have changed pre-filter, fuel filter, air filter, hydraulic filter, check hydraulic oil level wich is good.

Have also tried with a bottle with clean fuel, with lift pump hose in line inside the bottle

The thing is when I connect the line from the lift pump exit to the injection pump, the engine runs great !

 

[alfapillar]

stupid question, does the lift pump work once the engine is running ? I believe it runs only to start the engine, than the injection pump is in charge of fuel supply, or I'm wrong ?

 

[PoTreeBoy]

stupid question, does the lift pump work once the engine is running ? I believe it runs only to start the engine, than the injection pump is in charge of fuel supply, or I'm wrong ?

Most likely, it runs full time. Many engines have mechanical lift pumps that run anytime the engine is rotating.

 

[alfapillar]

Most likely, it runs full time. Many engines have mechanical lift pumps that run anytime the engine is rotating.

thanks for answering, this one is electrical, however, still the mistery of why working when electrical pump is connected straight to injection pump

 

[Russell King]

For trouble shooting purposes try these ideas

Rig the fuel bottle above the electrical pump so that there is some gravity head I guess even a syphon from a couple feet above would probably be okay.

Reverse the filter and pump arrangement from pump to filter to injection pump to filter then pump then injection pump

It seems like the filter is causing the problem with fuel flow and may need to be replaced with some new filter arrangement

 

[alfapillar]

For trouble shooting purposes try these ideas

Rig the fuel bottle above the electrical pump so that there is some gravity head I guess even a syphon from a couple feet above would probably be okay.

Reverse the filter and pump arrangement from pump to filter to injection pump to filter then pump then injection pump

It seems like the filter is causing the problem with fuel flow and may need to be replaced with some new filter arrangement

all filters are new

Will try this setting and see what happens, but have some kind of doubt, I've try a setting with : fuel tank - prefilter - feeding pump - 2nd prefilter ( with no flow direction ) - injection pump , and engine will stall

It's acting like engine will work with the fuel supplied by the electric pump than dies, except when the electric pump is plugged straight to the injection pump

 

[lugbolt]

Look at a fuel system on a G series or BX series

they are dirt simple.

Tank--->filter---->electric pump----->filter----->injection pump. The two filters are the same, 12581-43012 is the part number.

Sounds like your system has a filter problem, if you bypass one filter and the engine won't sustain under load, then the filter you bypassed is either (A)-plugged, or (B) has an air leak at the line, filter, whatever.

 

[PoTreeBoy]

Start at the beginning. When did this problem start? What was changed?

 

[alfapillar]

Look at a fuel system on a G series or BX series

they are dirt simple.

Tank--->filter---->electric pump----->filter----->injection pump. The two filters are the same, 12581-43012 is the part number.

Sounds like your system has a filter problem, if you bypass one filter and the engine won't sustain under load, then the filter you bypassed is either (A)-plugged, or (B) has an air leak at the line, filter, whatever.

Filters are new, have changed lines as well

 

[alfapillar]

Start at the beginning. When did this problem start? What was changed?

No idea as bought it as used unit, with this problem

 

[woodman55]

Does the engine you took the filter assy off of run well with it installed? When you bypass the filter do you use different hoses, most likely. Try a new hose between the inlet of the filter and the pump with the original filter assy installed, the inner wall of the original hose may be collapsing on the inside, restriction the flow.

 

[lugbolt]

as i understand it when u bypassed the filter it ran fine, right ?

if I understand that correctly, then you have isolated your issue to that filter. Restricted, collapsed, incorrect filter for the application, air leak at the line/filter, whatever

 

[alfapillar]

Does the engine you took the filter assy off of run well with it installed? When you bypass the filter do you use different hoses, most likely. Try a new hose between the inlet of the filter and the pump with the original filter assy installed, the inner wall of the original hose may be collapsing on the inside, restriction the flow.

yip the donor runs fine ! all hoses are new, except the one from filter to injection pump, as it works fin when by-passing the filter, didn't change it, but will do tomorrow.

 

[alfapillar]

as i understand it when u bypassed the filter it ran fine, right ?

if I understand that correctly, then you have isolated your issue to that filter. Restricted, collapsed, incorrect filter for the application, air leak at the line/filter, whatever

Yip exactly, by-passing the filter, the engine runs great. but not sure that it's isolated to the filter, will explain in the nex message

 

[alfapillar]

well today, have changed the prefilter, just in case but nothing changed.

Have disconnected the return line that goes into the injection pump, and surprise no flow from it once the engine start, but have flow when using the feeding pump .... have started to dismantle injector lines, but been stopped by other things, so will continue that tomorrow, and check if injector get their fuel, otherwise sounds like an injection pump problem, or I'm wrong ?

 

[PoTreeBoy]

i thought I had posted earlier to check that your lift pump runs full time. I'm thinking your injector pump has enough suction to pull fuel through everything but that final filter. But needs the lift pump to supply enough pressure to get through the filter.
Also, does your model have the primer valve on the injector pump? Open it to purge the air and close it after it's purged.