Lift pump problem for Bobcat CT230 (Kioti CK30 HST)?

[johnsopa]

Hi folks. My Bobcat CT230 (same as the CK30 HST) is bogging down when under load at RPMs over 2k.

Air filter is good. Fuel filter replace several times. There's good fuel (drained/replaced three times). Injection system has been bled a couple times. All to no avail...

However, I think I've found the issue. I shined a light through the clear plastic fuel filter housing and I now realize that the housing is not quite full. It ranges from half full (when checked immediately after bogging) to about 1/8" from the top of the housing (when idling for awhile).

There is no leaking in any of the lines going to/from the filter housing.

When I disconnect the line coming from the fuel tank to the lift pump, there is nice clear flow of diesel. Gas cap removal doesn't change the flow rate, so I think the vent is fine on the cap.

When I remove the output line from the lift pump and put my finger over the output, there is a little bit of pressure but not much. I can very easily stop the flow.

I replaced the line going from the lift pump to the housing so it's not clogged.

There's no leaking at the housing and the off/on/air valve appear to be working fine.

I'm not a diesel expert, but I think the fact that the fuel filter housing isn't full is bad and is the core problem.

Does this point to a lift pump problem? Specifically, if the fuel filter housing isn't staying full, then it seems to me that the lift pump isn't supplying enough diesel under pressure to the housing.

Am I thinking right here?

Thanks!

 

[Billrog]

I do not think it's your lift pump , possibly the governor but then I'm no mechanic. When you say bogging down is that when your sitting still or working the machine? high , medium or low range.

 

[k0ua]

Let me ask this, when idling the tractor for a while does the fuel bowl eventually fill up under this very low fuel usage scenario? Then when you place the engine under load is it a fact the fuel bowl is not filled as fast as the engine uses fuel? Perhaps the fuel pump is defective.

 

[roadhunter]

Might look for a kink or bend in the hose that is preventing flow or the possibility something is in the line preventing flow. In that case some air pressure on the tank might push whatever is in the line out into the fuel water separator.

Another thing that could cause that problem woudl be an air leak somewhere in the system when it goes under vacuum as fuel is being sucked. Might check the seal on the fuel water separator as well as the air bleed screw.

 

[tman1020]

Two things come to mind. Do you have the correct fuel filter and if so check to make sure it is installed properly and nothing is blocking the passage on the inside where it connects to the tractor. Some guys have had problems with aftermarket fuel filters not fitting correctly to the tractor. Secondly I believe there is a purge setting on the shut off valve to your fuel filter. Check in your manual to follow proper fuel filter replacement procedure if you haven't already.

 

[ritcheyvs]

Lift pump. The filter SHOULD be full of fuel at all power settings. Lift pumps aren't that expensive (like $50) but you can open it up and check for a cracked diaphragm or debris blocking one of the check valves,

 

[johnsopa]

Let me ask this, when idling the tractor for a while does the fuel bowl eventually fill up under this very low fuel usage scenario? Then when you place the engine under load is it a fact the fuel bowl is not filled as fast as the engine uses fuel? Perhaps the fuel pump is defective.

James, eventually, it will fill when idling -- but it takes a long time.

 

[k0ua]

James, eventually, it will fill when idling -- but it takes a long time.

Lift pump... It sounds like your pump is defective in some way. Hole in the diaphragm likely. Take it apart and check it out.

 

[johnsopa]

Lift pump. The filter SHOULD be full of fuel at all power settings. Lift pumps aren't that expensive (like $50) but you can open it up and check for a cracked diaphragm or debris blocking one of the check valves,

OK, I think this is what I needed to know. So, under full power, if the filter/housing should be full of fuel at all times, and it's not, and if the lift pump is getting a clean, good flow of fuel, and if there are no kinks or blockages going from the lift pump to the filter/housing, then the lift pump is the likely culprit.

Just ordered one (only something like $35 from the Bobcat dealer, surprisingly) so will try it out when I get it.

Thanks everyone!

 

[ritcheyvs]

Supplemental: The lift pump is a simple diaphragm pump. The diaphragm is spring-loaded to push fuel out of the pump at a couple PSI and pulled back against the spring by a cam in the engine. This pump is upstream of the filter so debris could get into the pump and jam one of the check valves, which would definitely reduce fuel flow and pressure. But if the diaphragm is cracked fuel can migrate from the pump into the crankcase, which may cause the engine oil level to raise, but maybe not enough to notice. If you suspect a significant volume of fuel got into the engine oil you should change the oil.