shuts off when jumper cables removed

[David_Kb7uns]

I could understand why a car would stop with the short and ignition being too much load for the alternator at low rpm. But a tractor with only 100 hours on it sounds like it would be new enough that it would have a fuel shutoff solenoid that would only be energized when you turn the key off. It would normally NOT be energized. Did I miss something???

Sounds like for some reason there is enough charge in the battery to pull the key stop solenoid in once the key stop/safety timer relay looses power and goes into the shut off mode.

I would check to see if there is a fuse or link that is burned on the circuit coming from alternator or dynamo and make sure if it has a dynamo that the regulator is good.

David Kb7uns

 

[catfishdaddyengineering]

It is not a typical short (like in the cable/system that would drain the battery), but it is in the battery itself. It is almost like you took a cable and jumpered across the positive (+) and negative (-) of the battery terminals. The battery will not charge, and the system will not run without the battery disconnected because it is a hard short.

He doesn't say how old his tractor is. 100 hours for some people could be 1,2,3,4,5,15 years old. I replaced my 3 year old battery with 300 hours on it because it sits outside and split the case. Found it because it would not hold the charge and was hard to crank without jumping off.

 

[LD1]

You have been given great advise so far. Do the checks others mention. I would certainly figure out what the problem is before I spent the money on a new dynamo or modified wiring

 

[sailorman]

Identical situation happened on my B2320 . Had battery completely tested at auto supply store and it was bad . New battery and no problem since . That was a year ago .

 

[robbyr]

I unexpectedly started having cranking issues with our Kubota RTV. Could jump it off and ran fine til you switched it off. Checked battery with multimeter (not under load) and it showed 12.88 VDC. So I thought maybe the alternator wasn't charging. Not a mechanic by any stretch but after trying to figure it out for several days I finally bought a battery. No problems since.

 

[Soundguy]

load testers help you out i these cases. 100-500a ver are available pretty cheap at HF. if you own many battery powered vehicles.. not a bad purchase. most of them also have a load setting for testing charge output as well.

 

[k0ua]

load testers help you out i these cases. 100-500a ver are available pretty cheap at HF. if you own many battery powered vehicles.. not a bad purchase. most of them also have a load setting for testing charge output as well.

I used to borrow the one my boss had, It sure was handy.

 

[robbyr]

You talking about those battery testers with the big alligator clamps to clip on the battery then push a switch to put under load and watch the needle? If so, I need to get another cuz I did have one but it quit reading accurately for some reason. Was old though.

 

[k0ua]

You talking about those battery testers with the big alligator clamps to clip on the battery then push a switch to put under load and watch the needle? If so, I need to get another cuz I did have one but it quit reading accurately for some reason. Was old though.

yep, just a big calibrated resistor and a meter. Puts a nice load on the battery to see how it holds up.

 

[Soundguy]

yep.. probably nichrome wire.. like from a toaster.. etc..

 

[chim]

My first guess would be bad battery. "Bad" in this case is high internal resistance -AKA dead (as opposed to a short). An alternator requires outside power from the battery to generate electricity. Old cars with dead batteries and generators could be jumped and they would run unless the load on the generator was too great. Residual magnetism in a generator provides enough field strength to make it work.

Alternator-equipped machines with truly dead batteries will die as soon as the jumpers are removed because there's no way to excite the alternator.

Edit to add: A bad connection or "open" internally is possible in a fairly new battery. Several years ago I had a dead battery in my truck. That particular battery had both top and side terminals. When they ran a test on it, it was only dead on the side terminals. It tested fine on the top terminals. It was a relatively new battery and was replaced.

 

[Soundguy]

except he has a dynamo.. that's essentially a permanet magnet low output fixed field alternator. no power input needed for excitation.

My first guess would be bad battery. "Bad" in this case is high internal resistance -AKA dead (as opposed to a short). An alternator requires outside power from the battery to generate electricity. Old cars with dead batteries and generators could be jumped and they would run unless the load on the generator was too great. Residual magnetism in a generator provides enough field strength to make it work.

Alternator-equipped machines with truly dead batteries will die as soon as the jumpers are removed because there's no way to excite the alternator.

 

[chim]

except he has a dynamo.. that's essentially a permanet magnet low output fixed field alternator. no power input needed for excitation.

I thought there were generators (dynamos) and alternators. Kubota says they use alternators Any further info would be appreciated.

 

[Soundguy]

I thought there were generators (dynamos) and alternators. Kubota says they use alternators Any further info would be appreciated.

on the low end of the food chain you basicalle have a permanent magnet dynamo that makes ac volt output that is then rectified and regulated in an external regulator. there is no field control. it's a ball of wire spinning inside a fixed magnetic field ( ie.. magnets glued to the inside of the casing ). it's low output.. but fairly reliable.

then you have the standard old style DC generator. .. basically 2-3 types.. 2 brush regulated and un regualted, and 3 brush ... all have field coils instead of permanent magnets. the external regulated ones use a 2 or 3 bobbin external mechanical voltage regulator to control field current.. the contact literally vibrates open and close to power the field, and thus vary field current. as field strength changes, so does output strength on the armature. the genny has a built in comutator which is just a clever wireing scheme with brush pickups so that the output of the generator is actually DC.. it's bumpy ugly dc.. but it is DC..... other variants use a 3rd brush to control field current manually with a dial moving the 3rd brush.. some also use a 'tickle' switch tied to a lamp switch that is essentiall a fixed resistor controlled field circuit... most of those fixed ressitor types have a hi / low setting depending on lamps or switch position.. different manufacturers used different versions.

then you get the alternator.. whole new ball game.. harder to explain without getting techno-geek... but it is also variable field.. uses a stator, has a diode trio and produces essentially 3 phase ac that is rectified in the alternator. alder alts use a external regulator.. somewhat like an old style generator reg.. some use a solid state built in reg. just depends on what ya got.

I've seen tractors that use all 3. I'm not a kubota guy. OP stated dynamo. I answered based on 'dynamo'.....

 

[Leejohn]

Tractor should run even without a battery or alternator, just couuldn't shut it off with the key. Check the fuel shutoff solenoid relay-timer, it's bad. The battery could also be bad?????

 

[Tx Jim]

Tractor should run even without a battery or alternator, just couuldn't shut it off with the key. Check the fuel shutoff solenoid relay-timer, it's bad. The battery could also be bad?????

Please explain how the engine can run with no battery or alternator attached? I'm not stating your statement is incorrect I just want to know "HOW/WHAT" controls the fuel with no electricity?? Thanks,Jim

 

[Soundguy]

many diesels have a fuel lift pump built into the front end of the injection pump.

some machines also have cam driven fuel pumps, not to mention.. many times tanks are perched for gravity feed to the IP.

all depends on the setup...

as long as nothing is killing a fuel-shutoff solenoid. a diesel .. an older diesel.. don't need a battery..

With a striaght gear trans, you could park on a hill, roll her started and run all day as long as you had say.. a mechanical oil pressure gauge and not an idiot lamp... and never need a single volt / amp of electricity.. at the end of the day, fuel up and park on the hill again. I know some farmers that have tractors with bad starters that STILL do that... couple that with manual fuel kill cables like my ford 1000 series have.. and you are good to go.

 

[k0ua]

My Kubota B7500 had a manual fuel shut off knob/cable. Start her up, and throw away the key. As long as you didn't pull that knob out, she would run all day.. The instrument panel didn't work but the tractor run and operated fine.

 

[robbyr]

I think my dad's L2600 will do the same thing.

 

[Tx Jim]

But not on a Kubota B2320 which is what this thread was started about as it has an electrically operated fuel controller