Looking for help. I have a Kubota kx121-3 st excavator that I can’t get to fire and run. I thought bad gas was added to the machine because it would cough and stall like it was starving for fuel. Eventually it quit all together. I drained fuel tank inspected all lines and water separator. I installed new glow plugs even though the old ones seems to test fine. I replaced injectors also. After this I started it up and it ran fine for twenty minutes or so before I shut it off. Upon trying to restart it it again refused to start. No fire no smoking nothing. I replaced the fuel filter and fuel shut off and it’s still a no go. I bleed the air at the head and is is getting fuel to the top of the injectors but doesn’t fire. I’m at a lost at this point and hoping there’s something I’m missing someone can point out to me. Any help would be appreciated. Thanks
Not sure on that machine but bad lift pump maybe?
I put a new lift pump in it. The old one worked too but I thought maybe it was a bit slow so replaced it. This engine is in several different machines.
To bleed those all you need to do is turn the key to the run position, don’t crank, and it should just bleed the air out. Leave the key on for for a few minutes.you should hear the lift pump pumping, sounds like ticking. Also, any chance you have a bad fuel line or bad pickup in the fuel tank? Is the tank full?
All a diesel needs is fuel and air and adequate compression and it will fire, or produce a lot of smoke at the least. No fire, no smoke, means it's not getting any fuel or the intake is totally restricted, stopping air flow to the engine. Is there any electric solenoid that controls fuel that is not functioning? Is there a hose anywhere that could have an internal failure? I've had the inner lining of a hose peel off and bunch up inside, totally blocking flow. There's also the possibility of a foreign object that is blocking fuel flow when engine operating suction is applied, but will let fuel flow when you're hand priming. I can recall one time we had a tiny piece of circular metal from the centre of a punching, end up in a fuel line. It was a neat fit in the (steel) line, and when suction from the pump was operating, it would flip to the 90° to the fuel line position, and act like a clack valve, and block fuel flow completely! It was an infuriating job trying to find the problem, and it was only found by running a length of wire through the line.
I thought the fuel may have had water in it so I removed the tank all hoses and clean everything. Replaced tank blow out fuel lines reattached. I wasn’t aware you weren’t to let it crank over. If I don’t crank the engine over how does the fuel get to the injectors? Isn’t the lift pump just to keep fuel flowing to the injector pump? yes fuel and air is getting to the motor. My final guess would to be a compression check. But the machine only has a little over a thousand hours and are easy hours. Would a compression issue happen with such little hours?
Does the IP have a knob you turn out to bleed it? I've heard of Kubota's sometimes being a pain to bleed. Mine was one time in the winter when I didn't warm it up a little before changing the fuel filter. If you're getting smoke try leaving the glow plugs on for a minute.
Kubota engines are well built and normally 100% reliable, if the engine has had an easy life, and has only done 1000 hrs, I couldn't see any reason to have a lack of compression problem. Their biggest weakness as with all Japanese equipment is their electrics. Does it have engine protection devices (oil pressure failure/overheating) that could be faulty and failing to allow the engine to operate? I've just had an issue with a B-series Cummins in a Lincoln Electric welder that was shutting down intermittently. We suspected a faulty engine protection device, and checked them all and found them all working - but eventually we traced the fault to the Hobbs hour meter, that had an intermittent internal short circuit, which was causing the engine shutoff solenoid to operate, when the short circuit was occurring! We never completely figured out how that was happening, but we replaced the hour meter and the problem ceased! We suspect the short circuit was creating a voltage imbalance in the wiring to the engine protection device that simply caused it to register a potential problem, and thereby activate the shutdown solenoid.
If it's the older indirect injection version they need more glow plug time even on warm days to start. It doesn't hurt to leave the glow plugs on longer than 15 seconds. In the winter a minute isn't uncommon. That's why I suggested it. Also move the throttle to full. Once it fires you can move it back to idle.
No there’s no knob to bleed. I do notice air bubbles at the injector head while trying to bleed it out. I have closed off all lines into the injectors once the bubbles stop thinking the air is out. I’m also not getting any smoke which says the fuel isn’t igniting.
Take the fuel cap off. I lost mine and replaced it with another that was supposed to be a vented cap. It wasn't and the machine wouldn't start. I discovered this when I took the new cap off and there was considerable pressure/vacuum released. Returned that cap and got a vented Stant cap and problem solved. Any way you could put a little air pressure into the fuel tank? Another thought is a bad wire or connection if it shuts off with the key that finally quit altogether.
I My fuel cap was pretty nasty looking on the underside and was thinking from the moisture in the tank over time. All rusty and caked with it. I just bought a new one to change out while doing this fix. I’ll be using the new one. Had to replace the fuel sensor too that’s inside the tank because that also was covered in thick rust not allowing it to work. So I’m replacing that too. But I can’t see how those two things can keep it from starting especially since it was running while those parts were on it. I’m not thinking it’s a bad wire because it did start when I replaced the injectors and GP and ran for about twenty minutes. The problem started again once I shut it off and it wouldn’t fire again. I’m going to try these things and see if maybe I wasn’t doing something right with the bleeding off the air. I’m just at a loss at this point.
I don’t think I have any engine protect devices on this machine but I could be wrong too. I have a mini screen that tells me when to service it and what to service with codes. And like I stated it was running fine after I replaced the GP and injectors for like twenty minutes. The problem didn’t happen again until I shut it down with the key and went to restart it. Nothing not even a cough.
I wasn’t aware you only needed to turn the key to the first position and not all the way to crank it over. I thought the engine cranking sends the fuel to the injector heads. Yes the lift pump will start at first turn put it doesn’t send the fuel to the injectors as far as I thought. Everything in the tank was cleared out and lines were all checked with no issues.
I’ve looked at everything that would make this motor not start and I’m stumped. Is there any chance the glow plugs are not getting hot enough or the compression is being lost preventing a start? There’s no smoke of any kind coming out of the exhaust yet it’s getting fuel to new injectors. I’m assuming the alternator sends power to the plugs?
I wonder if the shut off valve on the water separator could be plugged with junk. Does the lever with the red end move when you turn the key on and off? If it was a glow plug issue you'd still get smoke if you were getting fuel. It really seems like you're not getting fuel. Did you put the throttle to full when trying to start it and is spinning pretty fast?
Nope fuel is getting to injectors. Took all the water separated off and clean it blow out lines. Fuel is feeding injector pump.
Plugged injectors or not enough pressure to open them? If the cylinders are getting fuel there will be some type of smoke or raw fuel mist.
New injectors. No smoke nothing so I’m headed in the direction of pressure or electrical
Yes I am on the same thought but there’s fuel at the injectors. So could it be glow plugs not operating properly not getting hot enough? Or compression issues?
The level with red end is the manual fuel shut off right? It doesn’t move unless I move it
Wondering if the electric fuel solenoid isn't working properly. Glow plugs would have nothing to do with a fuel issue. If you think they aren't heating enough, do you have a block heater you could plug in? I have a feeling it's something simple why it's not getting fuel and/or not starting.
Dave I replaced the fuel shut off too. This is why I’m starting to think possible electrical or compression. I also am thinking it’s something simple since I replaced all known fuel system parts. Again it’s got me stumped. I’m going to look for some type of safety switch that might be to be replaced or reset
If you disconnect the glow plugs, will it fire on ether? Disable the glow plugs before you try.
Have not tried ether was told it wasn’t good to use on diesels
It isn't good, but you are only supposed to use a little shot for diagnostic purposes here. Make sure the glow plugs are disconnected, have somebody crank and give it a little shot. As Oz mentioned, you need air, fuel and compression. If it pops off on alternate fuel that tells you that you have air and compression. Just eliminating basics.
A tiny shot of ether is fine without the glow plugs. Just don't think if a little is good more is better.
Hey I’m going to give it a try. At this point anything is helpful. I’m just trying to limit all the easy things before I get too aggressive on it .
This machine is timed for starting. Meaning the voltage is shut off to the glow plugs after 5 seconds.
Ok have ether a try and it did pop off and run for few seconds. But how does getting it to run on ether make the glow plugs ok if they are disconnected?
Why hasn’t anyone pm’d me.?? Just because you replaced the shut off solenoid, doesn’t mean the pump rack is moving.. In other words, just because you can hear the solenoid clicking, doesn’t mean the pump is doing its thing.. So you’ve taken the lines lose AT THE INJECTORS and there’s no fuel squirting out.?? That’s an easy one.. u have fuel going in, I’m assuming you checked, and nothing out.. it’s the pump..
Yes I remove the lines at the injectors and I stated it was getting fuel. So I removed the solenoid and that didn’t work so it’s not that. Yes I’m left with the injection pump
You should be seeing a distinct pulse of fuel at the injector near each TDC with injector lines cracked, as you're cranking. This shows the injection pumps are pumping. If there's simply "fuel" at the injectors when the lines are cracked and the engine is being cranked, then the injection pump rack is not open. You can have fuel coming out of the injection lines at the injectors with the injection pump shut off, this simply shows that the fuel transfer pump is operating. If fuel is being injected, even if the glowplugs are not working at all, you will get exhaust smoke.
Getting it to run on ether has nothing to do with the glow plugs. What you have proved is that the engine starts and runs on alternate fuel, which means your problem is fuel. Compression and air are good. If you spray ether into the intake while the glow plugs are lit it can wreck the glow plugs, that is why I said to disconnect them. The glow plugs aren't the problem here.
I’m getting fuel to the head injectors but it seems weak not spraying out hard. I’m going to remove the injection pump and inspect it. Hoping it’s just clogged
Careful, IP's are tricky business, one doesn't just tear one apart and clean it without having a thorough knowledge of what's going on in there.
Yup I understand. I’m pretty schooled in taking things apart with out screwing things up. Diesel hasn’t been one of my things until lately that’s why I’m seeking information before I tire into it. I appreciate all the help everyone has giving me on this site.
I wouldn't take the IP off. Follow the pumpguy's advice. He is the expert on injection pumps. See if the fuel rack is moving. I highly doubt you need a full IP rebuild with only 1000 hours on the machine. It might not be a bad idea to have someone experienced with Kubota IP's have a look at it. Too much ether can ruin your engine. A tiny shot like you tried won't hurt it. Ether with glow plugs could blow the heads off!
I didn’t use ether I used a starting fuel and the heads aren’t blow off because the plugs weren’t connected. I don’t know where you got they were connected from
Found the problem
Just saying what could happen. Starting fluid generally has ether as the main ingredient. So what was the problem? Is that piece part of the IP?
I used a starter fluid that is labeled useable for diesels and yes your right there was ether in it about 30%. That that part is from the IP. It’s the engine idler pin that sets the IP slide it looks like. The slide itself has scuff markings on its end that makes contact with this pin showing that both pin and slider were smashing into one another but became out of alignment and bending the pin. Looking to order a new one today and hope it’s the issue.
Kind of bizarre how it could get bent. Was somebody slamming the throttle lever hard or trying to force it further than it would go, maybe trying to get the engine to shut off? I would think there had to be some kind of abuse to cause that.
This machine hasn’t been used hard at all and has never had the throttle slammed. I was able to get a new pin and install it along with taking the pump apart and inspecting all the components and nothing showed up bad. But now I have a new problem. I had to remove the auto idler cable while inspecting and when I went back to reattach it the cable has retracted back into it sleeving and I can not now get it to pull back out far enough to reattach it to the mount. Traced the cable to a motor up under the front of the cab where your last foot rests and before I mess with it I need to know why it will not extend back to attach.
I meant left foot
Did you get it running. Was the idler pin the problem?
The problem was the injector pump. I went through everything and in the end it was the pump