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Kubota Diesel

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Any one here with any experience with a 3 cylinder Kubota ? I got a 721D Grasshopper that won't start.
*G*
 

JimDawson

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Short of catastrophic mechanical failure a diesel requires 3 things to run, Fuel, Compression, and Timed Injection.

The good news is that a Kubota engine is pretty simple to work on.

Will it fire on starting fluid?

I guess I would start out with the obvious, does it have fuel?

Then is the fuel getting to the injector pump? Is the filter plugged up? Is the lift pump working? Maybe replace the fuel filter (be sure to fill it with clean fuel when installing)

Is the fuel getting to the injectors? Crack open an injector line at the injector and crank to see if the fuel is being delivered.

Is the fuel cutoff working correctly?
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kvt

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Does it have glow plugs, If so does it get power to them to preheat and help start it.
but like Jim said three things, Fuel, Compression and injection timing. Sometimes extras to help start like glow plugs.
Fuel from tank, to pump, pump to injectors, if all that is working
then check compression after that start checking the injection timing.
I wish gas was that simple at times.
 
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Guess I should have started with what I have all ready done.
Upon visual inspection I noticed that the fuel lines had been replaced with 3/8" instead of the ¼" that it came with. Being the wrong size the hose clamps were cinched down till they mushroomed off the back side of the hose barb and were still not tight.
So I bypassed the two fuel filters and pump and set up a gravity feed temp fuel can. Then with fresh fuel I bleed the air screw on the pump and the injectors {While Turning the motor over} till all air was purged from the system. I checked the glow plugs and they were getting 12.5 volts. And air filter is new.
Decal on motor and air filter housing say's "DO NOT USE STARTING FLUID"
Still no start. Light white smoke out exhaust and seems like it wants to start.
In the morning my plan was to remove and bench check the glow plugs.

I will admit up front I'm a gas guy so was wondering if I might have forgot something.
Saving compression check for last because of pre-bent steel fuel lines.
Kubota 005 (Small).jpg
And yes I know the white plastic rod from the fuel solenoid to the pump is broken but it still moves the stop/start lever the right distance.
*****Thanks*********G**********


 

JimDawson

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If you have fuel delivery to the injectors, then I'm going with low compression, bad glow plugs, or a bad injection pump.
 

CluelessNewB

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Unlike my old Perkins (Mr Leaky) my 2 Kubota engines (different models than yours, tractor and boat) absolutely need glow plugs to start. Depending on the temperature 5 to 15 seconds of glow plugs is sufficient. I actually suspect you have a fuel problem and the engine needs a good bleeding. Diesels really don't like any air in the fuel lines. I believe there is an air bleeder circled in yellow below. You may want to find an owners manual for your specific block to verify this. Many can be found online. (I suspect your engine is a Kubota D722 block, here is a link to a marine version of that engine, cooling and exhaust systems will be different but the basic block should be the same: http://www.betamarinenw.com/Engines/Resources/Manual - Beta 10, BZ4#D8E09.pdf )

Kubota3.jpg
 
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kvt

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Glow plugs, Do you have a ohm meter, Check the resistance on each if they are out you should not get a good ohm reading between the lead and the block. Like an open circuit, I have had them burnt out by being held on to long.
Another thing to check is have someone turn it over as you crack the line lose on one of the injectors, does it spray out good. If you do not get a good squirt each time it is supposed to then you have a problem like air in the system, plugged input or something. If getting good flow at the injector connection, and the glow plugs have good resistance, then start looking at something like compression or timing. Had a Mercedes that jumped timing one time. Not fun.
 

jpfabricator

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If I run the 4000 ford out of fuel, the only way I have been able to get her fired up again is to drag it with the pickup.
Put the tractor in high gear and start it rolling then dump the clutch.
After it starts running it usually has to be drug a few more laps around the pasture to purge it completly.

Sent from somewhere in East Texas Jake Parker
 

dave2176

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Use a test light between battery + and the glow plug connector. That will tell you if the glow plug is open (bad).
 

jocat54

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Disconnect the glow plugs and try the starting fluid---I am pretty sure the reason for no starting fluid is the glow plugs and use just a very little cuz you can wash down the cylinder walls and possible score them up.

My old 3 cyl ford diesel is hard to start after running out of fuel or doing a filter change, takes alot of bleeding to get the air out
 
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f350ca

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Your engine looks to be the same family as the D600 Im using in the wood processor. I'll agree with them needing the glow plugs to start, even in the heated shop. The glow plugs are easy to twist off if they haven't been out in a while. Remove the buss bar and feed power to each one with a wire. If you get a good spark they're probably good but could be shorted(not likely).
You said the fuel shut off works with the broken rod but just to be clear, in the picture the arm is in the off position. Its backwards to my Kubota tractor, thats the run position on it. Just made up a cable shut down for the processor and built it backwards.

Greg
 

Ulma Doctor

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Guess I should have started with what I have all ready done.
Upon visual inspection I noticed that the fuel lines had been replaced with 3/8" instead of the ¼" that it came with. Being the wrong size the hose clamps were cinched down till they mushroomed off the back side of the hose barb and were still not tight.
So I bypassed the two fuel filters and pump and set up a gravity feed temp fuel can. Then with fresh fuel I bleed the air screw on the pump and the injectors {While Turning the motor over} till all air was purged from the system. I checked the glow plugs and they were getting 12.5 volts. And air filter is new.
Decal on motor and air filter housing say's "DO NOT USE STARTING FLUID"
Still no start. Light white smoke out exhaust and seems like it wants to start.
In the morning my plan was to remove and bench check the glow plugs.

I will admit up front I'm a gas guy so was wondering if I might have forgot something.
Saving compression check for last because of pre-bent steel fuel lines.
View attachment 127015
And yes I know the white plastic rod from the fuel solenoid to the pump is broken but it still moves the stop/start lever the right distance.
*****Thanks*********G**********
Hey gator,
the 3/8" line they replaced in the picture is an injection nozzle return hose.
it only returns leftover fuel that was not injected by the injector pump. it will have no effect on engine performance unless air is being introduced.
more likely one or more of the o-rings under the fuel return cap has been eroded, cracked, or otherwise introducing air into the system.
the reason they don't want you to use starting fluid is because of the explosion danger of shooting start juice into the precombustion chambers and setting it off with hot glow plugs
you can start it on start juice if you disconnect the power to the glow plug relay or otherwise disconnect power from the glow plugs.

white smoke is an indication of low compression or contamination of the combustion chamber.
compression temperatures are normally in excess of 1000*F when things are right, even in the lil diesels.

it may be best to think safety when performing the compression check.
when you remove the steel lines, the fuel pump will still develop thousands of pounds of pressure that will exit the pump through the fittings whether there is a line attached or not.
you'd do best to plan for that
the injectors(nozzles) in this engine are (High) pressure operated, the timing is set by the fuel pump.

i'd consider extraction of the glow plugs and go from there
i hope the info is helpful
 
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cathead

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When did this engine run last? Can you supply some history on the engine and a few details? How is the battery?
Diesels need to turn over at a fairly good clip to fire off. What is the temperature outside when trying to get it started?
Do you have the 15 second glow plugs or the 60 second ones? If you have a voltmeter on the rig, you can see a
voltage drop when you hit the glow plugs. Usually the glow plugs draw enough current to drop the battery voltage
at least a volt or so. If you don't see a voltage drop, the glow plugs are likely not good. Does the engine fire at
all when cranked? I have found that warming up the engine first will go a long way towards getting it running
if anything is marginal.

The problem can very easily be a combination of marginal things. This is especially true
in cold weather climates where any marginal thing is amplified by the cold.



Only maybe use a small waft of ether as last resort in my opinion...

  • :chemist:



Sometimes it takes a bit of detective work to get to the bottom of it all after which they run like a clock...
  • :sherlock:
 
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CraigB1960

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We had a 3 cylinder 15KW Kubota generator years ago. It was a bear to get it to start if you ever run it dry, which we did twice. Very difficult to get the air out of the lines. We used starter fluid carefully, but until we got the air out, it would not start. We had to crack the lines at the injectors as part of the purge. (carefully).

The glow plugs are critical to getting that engine started as well. We had one go bad, easy enough to ohm them out. But I suspect you still have air in the system.
 

jpfabricator

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In the past I have also cracked the lines and had someone crank it while I blew compressed air into the fuel tank. I just cupped my hand over the fuel neck and added a little pressure.
It made purging about 10 times faster than normall.
I have also used ATF in the filter, its a little thicker than diesel fuel and helps to really push the air out.


Sent from somewhere in East Texas Jake Parker
 

dlane

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I was always told white smoke means lean fuel burn , my tractor and truck both have lift pumps that supply the injector pump with plenty of fuel might check that and filter. using starting fluid is not good ,
if anything WD 40 is best in diesels
Let us know what the prob was when you get her figured thanks
 
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Gator, smoke tells me that you are getting some fuel to the injectors, though maybe not enough. You might still have air in one of the lines. Crack the nuts on all three at the injectors and crank her over, just make sure to stay clear of any spray as it will be under very high pressure and could penetrate skin under the right circumstances. That would not be good! When it appears that you have fuel coming from one of them without bubbles, go ahead and tighten up that nut. Once you get two of them purged she will probably start, so be sure to stay clear of moving parts. When I purge lines I tighten the nut while still cranking. Avoid situations where you stop cranking and then tighten the nut.

If you feel that you have the lines properly bled but she won't fire, skip the starting fluid (probably have a hard time finding that in Florida anyway) and use a plain old hair dryer. Remove the air filter and blow the hair dryer into the intake at a point as close to the intake manifold as possible. Let it warm things up for a minute or two, then crank her over while continuing to blow hot air into the intake. If she starts that way you then know that the problem is with the glow plugs.

If you feel that the problem is fuel related, or if you have difficulty bleeding the lines, pressurize the fuel system and check for leaks. You might have a point that is sucking air in to the system.

All of the things that the others guys have mentioned are good, too, but I thought I might be able to offer a few more tips and tricks.

Good luck!
 

ogberi

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Having owned a couple of old diesel VW Rabbits, I'm unfortunately familiar with diesel engines. All the advice here is spot on. They require only four things to run - Fuel, Air, Compression, and the on-off switch in the on position. A lot of diesel pumps have a lever or solenoid actuated lever that kills fuel delivery. If you have electrical wires going to the pump, I'd check that out. You could try pull or push starting it if possible. I had a diesel rabbit with a starting issue once. The relay wouldn't cut in with the key in the start position, allowing the pump to distribute fuel. But you could leave the key in 'Run', roll it 1-2 feet backwards with your foot out the door, then pop the clutch in reverse and she'd fire right up. Applying 'percussive maintenance' with a screwdriver handle to the relay sometimes fixed it for a while.
 

FOMOGO

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Had a hair line crack in a steel the suction side fuel line on one of my backhoes. Took a while to track that one down. It would start (not easily) but had absolutely no power. Good advice above, will be interesting to find out what it was. Mike
 
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I pulled the glow plugs for a bench check.
Kubota 013 (Small).jpg
The break off torque was under 5 Lbs. And the showed rust on the threads.
On the bench they passed the ohm test. And all three lit up under power with in 8 seconds.

I'm going to clean the threads and look up the correct install torque as they seemed too loose to me and showing rust might be a bad electrical connection.
Thanks for all the tips y'all.
Will report progress or lack of tomorrow . I got to go and find the Brute another plane ticket.
**Keep your powder dry*********G********

 
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After some cleaning.
kubota 018 (Small).jpg
*G*
 
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First thank you for all the suggestions.
As far as pulling or pushing it to start thats not an option with this unit.
kubota 019 (Small).jpg
kubota 024 (Small).jpg
The hydrostatic drive will not turn the motor over.

I'm going to install the clean glowplugs after I finish my morning coffee.
Updates to come.
*G*

 
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Hi Gator
I don't like ether start it can ruin the bores. But I have found that a twist of wire to hold a small piece of rag soaked in fuel mixed with lube oil set alight and held at the inlet manifold will get the most obstinate motor going. the flame and oil smoke sucked into the engine makes a mixture that the engine cant ignore providing the injectors are working. If you hold the injector pipe while the engine is being cranked you should Be able to feel the pulse of the pump as it injects the fuel, although this may be faint on such a small motor .
You can undo the high pressure lines to the injectors one turn and crank the engine fuel will come out of the pipe when the pump works. It will NOT gush out at high pressure because the pressure is only there when the injector is trying to stop the flow before the now developing pressure overcomes the spring loaded valve in the injector.
Brian.
 
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Thank You for that explanation Brian,
The lit fuel/oil mixture will be tried if the motor does not start after I put the clean glowplugs back in.
Out to do that now.
*G*
 
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Update:
Ordered a new fuel pump. Only took 10 days by slow boat to get here.

Replacing all the old fuel lines and filter with new.
kubota 034 (Small).jpg
I sure hate it when the warning comes in another language.
kubota 035 (Small).jpg
I don't use gasket goop. To my mind the gasket should do the job or it ain't a gasket. I paint mine.
kubota 036 (Small).jpg
New lines installed.All thats left is clean the tank and add fresh fuel.
kubota 038 (Small).jpg
This don't work then the injectors come off for cleaning and a bench check.
*G*
 
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Had to jump on a new project that rolled into the drive way.
Will get back to the 'bota in the AM when it's cooler.
*G*
 

dlane

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Hope it fixes it , they do start easier when eng temp is 70^
 
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