Kubota Electrics especially the starter

[David Jackson]

I have a 20 year old Kubota L3350DT which is a 32 PTO hp 4WD tractor with hydraulic forward and reverse shuttle transmission.

The mechanical part of the tractor has generally been reliable but the electric systems have not; especially the charging system and the starting system.

Last year I replaced the alternator and some years before that the voltage regulator. About a week ago I did all the tests in the Kubota FSM on both the regulator and the alternator. All passed. However my charging voltage at the battery is only about a half a volt, or at the most, when the engine is screaming; possibly 1 volt over battery voltage when the motor is not running. What could possibly be wrong?

Starting is also a big problem. For a couple of years I used one of those push botton hand held jobs instead of the key switch. I simply bypassed the tractor's system and jumped between the hot lead from the battery and the relay terminal. Worked fine.

This summer I decided to refurbish the tractor to original and am having nothing but problems. The main switch passes all the tests in the FSM yet sometimes will not send 12 volts to the black/white wire for the starter solenoid. This afternoon it started about 10 times in a row; I then moved the tractor around for about 5 minutes; shut the motor off and now it won't start; not even with the jumper.

What on earth could be going on? These electrics are not Joe Lucas but act as if they were at times! (For those who don't know, Joe Lucas, aka the Prince of Darkness, made lighting, charging and ignition systems for English motorcycles.)

Any help?

About an hour after the post. I put my charger on the battery in the start setting for about 1/2 hour and the tractor fired right up; using my jumper button, not the Kubota electrics. That would indicate a discharged battery may have been the problem but not why I would not get 12 volts through the wiring.

I did do a search but found nothing and so would really appreciate any expertise which someone would be willing to share! I am stymied.

David Jackson

 

[Berniep]

What on earth could be going on? These electrics are not Joe Lucas but act as if they were at times! (For those who don't know, Joe Lucas, aka the Prince of Darkness, made lighting, charging and ignition systems for English motorcycles.)

Q: Why do the English drink warm beer?
A: Lucas refrigerators.

From what I have read the problem with lucas stuff was mainly corrosion.
Get a little oxide on the connectors or in the switches and it can cause all kinds of problems. Maybe some contact cleaner in the switch. Maybe a new solenoid. Maybe clean connections to the generator/alternator.
Probably not much help but you brought up Lucas and I had to post my favorite electric joke

 

[guyrj33]

I think that is a good suggestion checking for loose or dirtyconnections.
Don't forget to check the ground connections also, including the starter bolts.

 

[David Jackson]

I love the Lucas Joke!!!

Connections and corrosion; I am indeed sensitive to that potential problem. I have made every effort to clean every connection I can get to! Berrymans, sandpaper, wire brushes, compressed air, dielectric grease, on and on.

The key switch is a sealed unit; I can't get to the contacts and there does not appear to be any place to spray anything into it either.

Here's a puzzler; The key switch passes all tests in the Kubota workshop manaul including the test where resistance is measured between different terminals of the switch at different switch positions. The resistance between the B (where battery voltage enters the switch) and the ST (the terminal which is connected to the B terminal when the key is turned to the "START" position is minimal; being on the order of .1 or .2 ohms; yet even though at the B terminal 12 volts is detected there is NO VOLTAGE at the ST terminal with the key in the "START" position. What could possibly be going on?

Here's a general question; Is starting a deisel (even the small one in my tractor) such a drain on the battery that it will lose its charge after 10 or 20 starts?

More Help Please!!!

David Jackson

 

[bigjohnkub]

This was a problem with the older L series tractors. The neutral/start wire left the key switch and went through several neutral switches to get to the starter. It requires 8 volts to activate the solenoid. Our fix , after checking all connectiions, is to install a three post starter solenoid close to the starter. Run a 10gs wire from the big post on starter to solenoid Positive post. Run 10 ga wire from other big post to starter solenoid where black/white wire plugs in. Put black /white wire to small post on solenoid. When you hit start on key, it will energize aux. solenoid and put 12v to starter. Hope this will help. As to reference values in wsm,I find very few that are accurate.

 

[David Jackson]

Hi Big John;

First of all; very interesting that you find the values in the Kubota Shop Manual inaccurate. Very intereting.

It is also interesting that you mention several neutral switches. My tractor will start in gear if I push the clutch in or bypass the safety clutch pedal switch; there is only the one switch which gets a circuit completed when the clutch pedal is depressed, that I know of. (A 1985 tractor.)

I have tested about everything and don't quite know what is going on. I have ordered a new key switch; did that before I read your post about the extra solenoid.

Also very interesting about 8 volts being all needed to energize the stock solenoid.

I tried to measure voltage at the small spade trerminal while cranking. The motor starts so fast the needle does not get past 8 volts before the motor is running. I held the key on the start position a little after the motor was running once and the voltage went up to around 10 volts before I let it go.

I got the key switch to work; somehow it started working after I put a fast charge on the battery and it has been working ever since (about 20 or 30 starts I would guess). Somehow I thought maybe the battery is weak. I put an ammeter in series between the B terminal of the alternator and the wiring; I got a charge of 15 to 20 amps briefly and then sometimes 5 to 10 amps at idle. Then after a few minutes idle produced no current. I have the old voltage regulator and put that back in; that gave better results by a little bit plus the current reading was steady. I swapped back and forth again and wound up leaving the old regulator in. My alternator checks out ... in the book that is; idle unregulated voltage is about 17! More with more rpm.

I am going to try the new key switch out and if that does not work out after a while I have two alternatives 1) try out your extra solenoid method and 2) wire up the starter to be able to plug in my pushbutton on wire starter (the way I had it for about 4 years!).

However; right now it is working like a champ. (If it ain't broke don't fix it?)

If 8 volts is all the starter solenoid needs then perhaps I have wasted the $50 for a new key switch. However, I would not expect a 2 to 2.5 volt drop from the battery terminal of the key switch to the ST terminal, would you?

Maybe there is something I am missing here.

David Jackson

 

[rbargeron]

Hi David - Reading down through this thread I didn't notice any mention of the fusible link. I've had trouble with them on my Lxx50's so I figured I'd mention it here. The fusible link is a small loop of special red wire with a white plug just above the starter motor. This link passes (and fuses) power to the starter switch. In my experience, they corrode internally, leading to the symptoms you describe - sometimes the starter switch works, sometimes not. Sometimes a fresh charge pushes enough electrons to make it function for a while, but if the battery drops to a slightly lower voltage, it fails again. You can test it by unplugging it and jumping the terminals with a piece of heavy copper wire. If it works it's ok to run that way for a while - but then there is no fuse to protect the starter switch wiring. The long-term answer is to replace it (part no. 36330-75380 - maybe 5 bucks).
Prompt cheerful refund if info is irrelevant. Take care, Dick B

P.S. I think Kubota buys these fusible links from Lucas

 

[ByteMe]

Had a similar problem with an older tractor. It turned out that somewhere along the way the glow plugs had been wired into the keyswitch in the run position instead of the glow position.

The plugs were drawing current any time the engine was running and would drain the battery. Just something to check for.