My 2015 L3901 has been dying suddenly. I get these codes P0606, P0627 and P0629. It will start back up immediately and run for a few seconds or a few minutes more. Water separator is clean and gas is flowing. The fuel filter is only 1 year old and I will replace it this week. Any idea on what the issue is? Also, where is the fuel pump relay located?
L3901 HST dies suddenly
- Thread starter AustinSC
- Start date
cliffboyer
Active member
Equipment
L3301 w/LA525 loader, G5200 mower w/RC48 deck, Kawasaki 610 Mule, DR mower
Had similar issue a while back on my 3301, but no codes. Fuel tank outlet was plugged. Did have visible debris in fuel bowl.
North Idaho Wolfman
Moderator
Staff member
Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Do you hear / feel the fuel pump running?
Have you turned the key on and opened the bleeder to see if it's moving fuel?
Have you turned the key on and opened the bleeder to see if it's moving fuel?
Yeah, it's diesel. I meant that the fuel pump is getting fuel and pumping but I'm not sure what the pressure should be or if it needs to be replaced.If not, I think I know what the problem is!
The first thing I did was clean the water separator and blow out the fuel line to the tank and yes, it was clogged. But the problem continues.
Yes, I can hear and feel the fuel pump working. I disconnected the line coming out of the fuel pump, turned the key on to see if fuel is being pumped out and it was. I put my finger over the outlet to see if the fuel pump would shut off once pressure built up but it never did. I have bled the air out of the fuel system as per the manual several times. The tractor will start up instantly each time after it shuts off.
Maybe your fuel shut off solenoid isn't working. Some solenoids have two coils. Once the key is released the fuel shut off needs to be active to keep fuel flowing. It that solenoid isn't working properly and closes you get no fuel. Not sure, just guessing.
North Idaho Wolfman
Moderator
Staff member
Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Yea, I like older machines!New Common rail engines don't have fuel shut off solenoids.
I don't think it is supposed to shut off. IIRC, the lift pump only needs to put out about 4-6 psi, so if it's burbling out, it's probably not the pump. With pressure that low, there's really no need for it to shut off or even have a bypass. But I don't know your tractor, so I'm guessing based on general principles.
Sure sounds like insufficient or intermittent fuel.
Perhaps something with the injection pump?Have you removed an injector to see what the spray looks like?
I am no expert but I dont think thats a good idea or likely to yield meaningfull information.
This engine uses a very high pressure common rail fuel injection system operating at 5000 to 25000 PSI. Each ignition event is four separate fuel pulses of different sizes and duration.
The size and duration is controlled by the ECU based on real time feedback from multiple engine sensors. Diagnosis requires special test equipment and sophisticated software and hardware.
Dan
I’ll 2nd this
The only way I’d be “testing” HPCR injectors is through a reputable injection shop, and I’d be testing the whole set together.
It would at least tell him if the injection pump is functioning at all, I think.
Again I am not an expert but this us not mechanical fuel injection and AFAIK there is no "injection pump" in a Kubota common rail system.
In common rail a high pressure fuel pump (HPFP) maintains 5000 to 25000 PSI fuel pressure in the common rail. That pressure is maintained by a pressure regulator and rail pressure can be checked using a fuel pressure test gauge. The ECU also monitors rail pressure in real time and sets diagnostic fault codes if its not correct. Those cades can be read using an appropriate scan tool.
The injectors are piezo-electric devices that inject that common supply of high pressure fuel into the combustion area of each cylinder. They are individually controlled by the ECU which uses signals from a multitude of sensors to determine the appropriate timing, pulse width, and magnitide of each injection event. On this engine there are four separate injection events for every ignition event and they are highly atomized and lightning quick (milliseconds). The injectors are tested and calibrated on the bench using specialized test equipment that measures things like pulse width, volume. and response time. That data is then loaded into the ECU as a timing map for each individual injector.
Blindly playing with this system is simply not a good idea and messing with the high pressure side (red) is dangerous
Dan
Last edited:
I had a broken wire on the side closest to the ECU that even if the seat switch was bypassed, would have caused me problems.
That said, if you had one chunk that you found that you cleared, it’s very likely that’s the only one you might know about. Have you had to use Biodiesel down your way?