Kubota Z402 Manual
Parts of this manual to be outdated. KUBOTA distributors and dealers will have the most up-to-date information. Please do not hesitate to consult with them. Service manual for the Kubota Z402-B diesel engine. 187 pages in English, French and German.
Kubota Engine Service Tips Johnson City Kubota & Equipment, LLC Kubota Engine Service Tips Engine will not crank at all The number one cause of this is dirty or defective battery cables. Please use eye protection before attempting this repair procedure! Remove the ground (-) cable from the battery first and after it is securely away from the battery, remove the positive (+) cable. Clean the battery posts and cables using a battery post/cable cleaning tool (available at your favorite auto parts store) or your trusty pocket knife if that's all you have.
If the cable is really nasty looking you may just want to go ahead and replace it to prevent a recurring problem. When re-installing the cables always attach the positive cable first and then the ground cable. This will prevent that unpleasant sparking which might cause a battery to explode or other bad things to happen. We have made dozens of expensive service calls to clean battery cables. Do it yourself and spend the 'service call' money on a nice night out!
Number two cause is, of course, a bad battery. A simple digital volt-meter will tell you a lot about the condition of your battery. A reading less that 12 volts is indicative of a battery that is failing or in need of charging. If the reading is 11 volts or more while you are trying to crank the engine see the check below.
Please, always charge your battery before buying a new one! Many, many 'good' batteries have been replaced unnecessarily. Number three cause is defective safety switches.
DON'T EVEN THINK ABOUT BYPASSING THIS IMPORTANT SAFETY FEATURE! If you think you might have a bad safety switch you can check it simply with an ohm-meter or a continuity tester. Remove the switch from the circuit (unplug it). If the switch will not conduct with the 'plunger' in either position you can assume that it is defective. If it does conduct, it may just be out of adjustment. Other causes include a blown fuse or 'fusible link'.
If NOTHING electrical works (lights,etc.) you probably have 'blown' the 'fusible link'. This is a loop of wire generally located near the starter.
They rarely 'blow' but it does happen. (Especially if you hook your battery up backwards!) If you know your battery is good, all safety switches are OK and the starter is not the problem, your engine might be 'locked up'. If the engine has been otherwise operating normally, one reason might be that 'junior' has stuck the water hose in the exhaust pipe and filled the crankcase and cylinders with water. This creates a 'hydraulic' lock, which will prevent the pistons from moving up in the cylinders thus preventing rotation. If you suspect this has happened remove all of the glow plugs, turn the engine over by hand to expel the water, change the engine oil and filter, re-install the glow plugs and give it another try. If it starts and runs normally, then change the oil again at least twice at 1 hour intervals. Now, go put your water hose in that cabinet that has a lock on the door.
Engine cranks but will not start I have a question for you. Do you see any 'smoke' at all when you are trying to start the engine? Well guess what? No smoke means no fuel is getting to the engine for some reason. Now I know you didn't run the tank dry (did you?) so check your fuel filter first.
Is it full of water or 'crud' (or both)? If it has been a while since you changed the filter(s) it's not going to hurt anything to go ahead and do it now.
If it's freezing weather and there is water in the fuel system (tank, filters, etc.) ice will form and stop everything. If that's the case your gonna have to 'drag' your tractor to a warm place to thaw out. There is NOTHING we are aware of that you can buy to pour in the tank to melt ice once it has formed! Another reason that you may not be getting fuel to the injectors would be a stuck fuel control lever on your injection pump.
If your tractor has a 'manual' engine stop cable (or rod), follow this rod out to the 'business' end at the injection pump. When you push in on this cable (or rod) to put it in engine start position there is a lever on the injection pump that is 'spring loaded' to follow it.
If it doesn't, there's your problem. You can usually push it into 'start' position with your fingers but you will want to soak it good with some penetrating oil to free it up properly. If you have fuel in the tank and the fuel filters are OK and you see some kind of smoke when you try to start the engine you may have enough for the engine to start.
Other causes include defective glow plugs or low cranking speeds from a weak battery. The best way to check glow plugs is to yank 'em out and hook 'em to a battery (ground on the body, positive on the connection end.) If they glow red, they're OK. (Watch that you don't burn yourself!) Another problem with glow plugs is found in the connection wires between the plugs.
These connections tend to corrode over time (just like battery cables). Clean them with some sandpaper before reinstalling to the glow plugs. If you don't want to test your glow plugs before replacing them, can I have your old ones? Glow plugs rarelygo bad folks. One cause I hate to mention (but have to) is that someone (not you, of course) has poured gasoline in the tank of your diesel tractor. Seriously, it has happened more often than you might think. We have not seen it 'ruin' anyone's tractor yet, so drain the tank, refill with diesel fuel, change the fuel filter(s), bleed the fuel system (including all injector lines) and hit the 'GO' button.
Now, Don't EVER let anyone else put fuel in your tractor again, OK? One note of caution concerning starting fluids in a Kubota diesel engine; DON'T DO IT! You WILL ruin your engine. The increased pressures from the resulting explosion are simply more than the pistons can tolerate. Diesel Engine Compression Diesel engines depend (in large part) on heat generated by compression in order to ignite the fuel-air mixture. As a gas (in this case the air/fuel mixture) is compressed, the temperature of the gas increases. Diesel fuel 'vapors' will ignite (if exposed to a flame source) in the 100-125 degree (F) range, as this is the 'flash point' of diesel fuel.
However, for 'spontaneous' combustion of the air fuel mixture to occur, the air must be compressed to the point that the temperature is increased to nearly 1000 degrees (F). Although starting is generally assisted by glow plugs, there is a minimum compression needed below which starting becomes a difficult proposition. A new Kubota diesel engine will develop pressures in the range of 450+ P.S.I.
If something happens to lower this to around 325 P.S.I. Starting problems develop and you will begin to notice a decrease in horsepower. The chief cause of low compression is the piston rings. They either 'wear our' because of dirty air infiltration or 'weaken' from overheating the engine.
If you think you may have low compression you can check for dirty air infiltration by removing the hose from the intake manifold and looking down in the manifold with a flashlight. Do you see any dirt down in there? If you do, you more than likely have what we in the trade call a 'dusted engine'. If the intake manifold is clean, think about how many times the engine has overheated. Overheated rings that have 'lost their temper' (no, rings don't get mad) can't expand to fill the gap between the piston and cylinder walls, thus sealing the compression gases. In either case the only cure will be at minimum a new set of rings. One other cause of low compression might simply be low cranking speed.
In order to develop 'peak' pressure in the cylinders, the engine must be rotated at an established minimum speed while cranking. If it falls much below this speed, it will not be possible to develop sufficient pressure for combustion to occur. A little side note.
You may be wondering why you have to 'preheat', although your engine is still very warm. Remember that the air you are 'drawing in' is much cooler than the inside of the engine and this serves to effectively reduce the temperature of the 'air-fuel' mixture below what is needed for combustion.
Engine oil level is increasing Call Exxon and stake your claim! No, what probably is happening is that your hydraulic pump is transferring oil from the transmission to the engine. This usually happens when the 3 point lift is 'out of whack' and is trying to raise the lift arms further than Mr. Kubota ever intended for them to go.
This is a very common problem with mid-mount mower deck tractors. Often the deck lift system gets out of adjustment (or was never right to begin with). Don't sweat it. Move the little do-hickey, at the rear of the slot that your lift lever works in, forward so that the lift will quit raising sooner. With the lift all the way up and nothing mounted on the 3 point hitch, you should be able to raise (with your hands) the lift arms another inch or so before they 'bottom out'. If you have corrected this and are still 'making oil', it may have progressed to the point that the hydraulic pump is too worn to contain it.
You guessed it. Another less frequent cause of this problem is a stopped up transmission breather. (Look under your seat for this.) Least frequent of all is a defective fuel lift pump allowing fuel to get into the engine. It's somewhat hard to tell but generally the engine oil will be thinner if fuel is the culprit. The nice thing about transmission fluid is that it has about the same viscosity as the engine oil so it won't harm your engine as long as you don't get too much in there. A large amount of fuel in the oil, though, can cause loads of problems so let's keep a sharp eye on those oil levels mates! Engine is overheating 99.9% of the time, this is caused by restricted air flow through the radiator.
When it's dry and dusty you might find it necessary to clean the radiator daily. The best method we have found is to blow through the fins with compressed air.
A garden hose with a hand nozzle does not develop enough force to do a good job of cleaning. Use caution if you have a pressure washer. What you don't want to do is bend all the fins over flat.
Manual De Taller Aixam Kubota Z402
Another cause is seizure of some component in the engine. This can occur after repeated episodes of overheating so that even if you have cleaned your radiator, you will still have a problem. Less apt to be the cause is defective thermostats and water pumps (though for some reason a lot of people like to replace those first). One freaky thing we saw happen (once) was a customer who continually put creek water in his radiator. The mineral deposits accumulated to the point that some of the smaller water passages between the cylinder head and the block became 90% blocked. I think this is a problem that would take a very long time to develop, however, so let's keep it as a last resort. It is assumed that you have checked the fan belt tension (not too tight, please) and you are using a 50-50 mix of antifreeze and distilled water.
If you are 'consuming' water over a period of time it may be due to a leaking cylinder head gasket or even a cracked cylinder head. One major point NEVER pour cold water into a hot engine. That is an excellent method for ruining the cylinder head. Engine runs a while and dies This could be caused by a restriction in the fuel supply system i.e. Some foreign object in the fuel tank that is blocking the free flow of fuel from the tank. On the other hand, your fuel filter(s) might be clogged with dirt. A diesel tractor with will do this as well.
You can usually smell the gas in the tank if this is the cause. Another cause is overheating. When the pistons try to expand beyond design limits, seizure occurs.
Blow your radiator out (the fins) with compressed air and try it again. Sorry, folks, the water hose will not get it clean enough.