KX040-4 Mini Excavator Fuel System Issue

[Pistol817]

I recently purchased a 2017 KX040-4. The fuel system was getting air in it an shutting down when running at high idle. I isolated the issue to the water separator bowl and got it fixed. I also noticed that the fuel pressure is negative 10-20 psi at full throttle and 0 - negative 5 psi at lower idle(constant vacuum on the system).

Here is what I have tried so far with no change in pressure:
Fuel filter - replace with new
Water separator filter - replaced with new
Completely bypassed filter and separator
Checked all hoses for kinks/blockage
Replaced 12V fuel pump
Added additional in line 12V fuel pump
Checked/cleaned tank

It appears to me that the system doesn't have any suction issues, but is bypassing via the injector return lines to the tank. The only way I can get the suction pressure to rise is to "pinch" down on the return/bypass lines. This causes a rise in pressure but the machine then kicks a "fuel pressure" code.

 

[GreensvilleJay]

curious, I looked online(KX040-4Ca) and there's a LOT of 'rubber' fuel lines with hose 'spring' clamps. It's possible one or more aren't tight enough and allowing air to be sucked in.
perhaps replace the 'spring' style clamps with 'gear' clamps ?
Over time , heat and vibration ,tend to loosen stuff up. Hopefully you have good access to all of the hoses.

 

[Pistol817]

curious, I looked online(KX040-4Ca) and there's a LOT of 'rubber' fuel lines with hose 'spring' clamps. It's possible one or more aren't tight enough and allowing air to be sucked in.
perhaps replace the 'spring' style clamps with 'gear' clamps ?
Over time , heat and vibration ,tend to loosen stuff up. Hopefully you have good access to all of the hoses.

Yes sir, you are correct, there are a ton of connections. I have changed several of these and seem to have the air issue resolve. Now I just can't figure out why I have so much vacuum on the suction side of the injector pump and so much fuel bypassing back to the tank.

 

[ruger1980]

First off where and with what are you measuring fuel pressure? Yes a negative pressure is a vacuum but vacuum is measured in inches of mercury or water. I would say if it is running strong with no faults or complaints you may be looking for a problem that does not exist.

 

[North Idaho Wolfman]

Yes sir, you are correct, there are a ton of connections. I have changed several of these and seem to have the air issue resolve. Now I just can't figure out why I have so much vacuum on the suction side of the injector pump and so much fuel bypassing back to the tank.

Where are you measuring a vacuum???

 

[Pistol817]

Where are you measuring a vacuum???

I’m using a harbor freight fuel pressure gauge connected to the air bleeder on the filter. I’m getting the same results downstream of the fuel filter just before it enters the injector pump. See attached pics.

 

[GreensvilleJay]

OK, I'm confused, so DOES the engine run fine without the vacuum gauge installed ?

 

[North Idaho Wolfman]

I’m using a harbor freight fuel pressure gauge connected to the air bleeder on the filter. I’m getting the same results downstream of the fuel filter just before it enters the injector pump. See attached pics.

What does the WSM say about it?

 

[Pistol817]

Yes, it seems to run just fine.

 

[Pistol817]

Some additional history; it has always had this fuel pressure since I got it. Then a few weeks ago it went into regen mode and wouldn’t come out of it.

Then it started giving a system engine error code 22 (exhaust inlet sensor). The code would reset if the key was turned off and back on. I continued to run it to complete the regen, but it sent a code for dpf clogged needs repair, system error code 22, and reduced hp.

I cleaned the dpf and found the sensor had a worn spot. Ultimately, took it to the dealership to get it reset.

They told me the dpf was fine, but the engine was starving for fuel and the sensor was bad. They had already changed the fuel filters, but wanted to change them again and clean the fuel tank for about $3,000.

I picked it up, did the work myself and didn’t find any issue with bad fuel or dirty tank. I replaced the $260 sensor and it’s still showing to be in regen and system engine error.

Kabota service said the fuel issue would need to be addressed before the dpf could under go a “forced” regen.

 

[Pistol817]

What does the WSM say about it?

I just bought one and have been going through it. I haven’t see anything that has really addressed the issue.

 

[GreensvilleJay]

great , now we get more 'history'.... the more we know, the better we can think about it...
No, I don't fix them for a living but after reading a few 1,000 posts here, I have a question, some 'sensor' was replaced, did you reprogram the ECU to update for the new sensor ??
It seems common here than any 'DPF' problems usually need the 'computer' (ECU ) to be reprogrammed. Have seen where ,when replacing injectors, the ECU needs to be reprogrammed so neding to tel ECu 'you have a new sensor' makes sense. After all each sensor probably has slightly different characteristics.
Perhaps one of the experts will reply

 

[GreensvilleJay]

Curious, found this at Kubota Canada. There's 3 sensors ! One unmarked, one gray, one black. So, question, which one was replaced and was it the proper sensor ? If it was the 'gray' one, did you SEE the gray marking on it ?
If you just 'bought and installed', it's possible it's not the correct sensor for that location.
Obviously those 3 sensors don't have the same charcteristics(temp range, slope,DVDT,etc. but probably will fit in any hole.
Again, hopefully one of the experts whose handled these 'sensors' will reply soon.

 

[Pistol817]

great , now we get more 'history'.... the more we know, the better we can think about it...
No, I don't fix them for a living but after reading a few 1,000 posts here, I have a question, some 'sensor' was replaced, did you reprogram the ECU to update for the new sensor ??
It seems common here than any 'DPF' problems usually need the 'computer' (ECU ) to be reprogrammed. Have seen where ,when replacing injectors, the ECU needs to be reprogrammed so neding to tel ECu 'you have a new sensor' makes sense. After all each sensor probably has slightly different characteristics.
Perhaps one of the experts will reply

I did not reprogram the ecu. Do you have a recommendation for a programmer or is this gonna be a dealership process?

 

[Pistol817]

Curious, found this at Kubota Canada. There's 3 sensors ! One unmarked, one gray, one black. So, question, which one was replaced and was it the proper sensor ? If it was the 'gray' one, did you SEE the gray marking on it ?
If you just 'bought and installed', it's possible it's not the correct sensor for that location.
Obviously those 3 sensors don't have the same charcteristics(temp range, slope,DVDT,etc. but probably will fit in any hole.
Again, hopefully one of the experts whose handled these 'sensors' will reply soon.

It was the one labeled 010 in the picture. It was identified and provided by the dealership when they had it.

 

[GreensvilleJay]

from what I've read here, the dealer has to do it.
I'd have thought the dealer's service manager or the parts person would have explained the process, if it's required.
time to twiddle thumbs for someone who knows ........

 

[ruger1980]

Where you are measuring is the supply side of the feed or lift pump I would not be surprised to see a vacuum there. If the electric pump is not running you would definitely see a negative pressure there.
Kubota is messed up in there terminology, typical Janglish. What they call the supply pump is the high pressure pump and what they call the injection pump is the feed or lift pump.
It is hard to tell with the WSM and a good fuel system diagram what the [purpose of the various lines and valving are in that fuel circuit. I could imagine it could be a pain to bleed the air out.

As far as the issue with regen it is more likely and issue where the regen is not fully completing and resetting the soot load. Do you still have codes and what are they? Replacing a sensor because you have a code for the sensor is just firing off the parts cannon. More often the issue is a plausibility code which means the sensor is not see the value it wants to see.

 

[North Idaho Wolfman]

Bottle feed the fuel filter (from above, gravity) and see what that does for you, that should eliminate any fuel delivery issues.

 

[GreensvilleJay]

hmm, looking at the drawing I posted and wondering IF the connectors can be put into the wrong location ? Should be unique keyed but.......

 

[Pistol817]

Where you are measuring is the supply side of the feed or lift pump I would not be surprised to see a vacuum there. If the electric pump is not running you would definitely see a negative pressure there.
Kubota is messed up in there terminology, typical Janglish. What they call the supply pump is the high pressure pump and what they call the injection pump is the feed or lift pump.
It is hard to tell with the WSM and a good fuel system diagram what the [purpose of the various lines and valving are in that fuel circuit. I could imagine it could be a pain to bleed the air out.

As far as the issue with regen it is more likely and issue where the regen is not fully completing and resetting the soot load. Do you still have codes and what are they? Replacing a sensor because you have a code for the sensor is just firing off the parts cannon. More often the issue is a plausibility code which means the sensor is not see the value it wants to see.

I agree with the firing of the parts cannon. That’s why I picked it up. I can’t afford the dealership guessing at $180 and hour and parts changing at $250+ a part.

I check the fuel pressure between the fuel filter and the supply pump. Should be swing the pressure the 12v pump is producing.

DPF codes attached.