Kubota KX41 Starter Saga

[aesmith]

The machine is a Kubota KX41 1.5 ton digger, the original model from the 90s. Kubota D1105-BH engine.

I'm struggling with two things, what's wrong with the starter, and where to source a decent replacement at a sensible price

The starter generally works fine, but It has episodes where it won't start, the lights dim but the starter does nothing, no click or anything. This usually when I come to start after it's not been used for a while, including when the battery has been on trickle charge.

I stripped down the starter, couldn't see anything wrong but cleaned up brushes etc. Back on the machine it worked right away. Perfect, until a few weeks or months when it did it again.

I've had two attempts at replacement, one was a cheap unit off Ebay that only lasted just over six months, the second a "WAI" branded supposedly European part which didn't last much longer. In both case they just got more and more sluggish until they struggled to start at all.

Any suggestions welcome.

For you pleasure here's the WAI first thing in the morning, battery on charge overnight ..

And swapping back to the old one, cold start next morning ..

 

[addjunkie]

When it doesnt go have you tried just bypassing everything and shorting solenoid out

 

[Nomad]

From experience working on cars - check all connections on the big battery cables (to starter, battery earth, engine block to chassis..)

As a quick test use a good quality jumper cable from the battery earth terminal (negative earth?) direct to a bare metal part on the engine (inlet manifold? alternator bracket?), I've had a few cars where earth cables looked ok but were failing inside or had a poor contact at the terminal due to corrosion.

 

[aesmith]

Thanks. The first time it started after fiddling around with different batteries and cables, as a result I replaced the battery and the battery cables so those are all known good. Return cable goes to a stud on the engine block right next to the starter.

I don't think I can short out the solenoid. It's a pre-engaged starter with the solenoid in the main body, and the motor piggybacked onto it (opposite of normal). If I bypass the solenoid (if that's even possible) the motor will spin, but not be engaged with the flywheel. I'm not explaining well, I'll see if I can find photos.

 

[Nomad]

That all makes sense ..

Not a lot you can do to check you pre-engaged starter as the solenoid (& engagement system) is all inside the starter - the older inertia starter motors are easier to test but afraid that doesn't help you..

 

[aesmith]

There is a theory that it might be voltage related, the solenoid not traveling fully and therefore not closing the contacts. That's a difficult one to test, and also you'd think that would mean it would always work if tried with the battery charger connected.

I should also note that neither of the two short lived replacements, Ebay Chinese or WAI, ever showed this symptom, which to me suggests it's an issue with the starter and not the machine or wiring.

 

[Barking Mat]

What size engine is it ?

You'll probably find you can unbolt the end cap, remove the plunger, wife brush the hell out of it and it'll probably run like new.

Can you post a pic of the starter ?

 

[aesmith]

It's 1100cc. Will post pictures tomorrow. I have to say that everytime I've stripped and cleaned the starter it's worked fine afterwards. It just doesn't stay working and the same fault pops up weeks or months later. It never fails on the bench either, even if not working before I removed it from the engine.

 

[m_c]

Just had a quick google, and I see it is the type of starter I thought it was.
Have you tried stripping and re-greasing the reduction gears?

The few of that style of starter I've dealt with, usually either the solenoid fails completely, or they seize.

 

[jsf55]

When it doesnt go have you tried just bypassing everything and shorting solenoid out

Good idea as it could be the ignition switch failing ?

 

[Jack_K]

I find that pre-engaged starters have issues when switches get old unless a relay is fitted. The solenoid itself draws a lot of current so many vehicles fitted a relay but not all. It can cause intermittent starting. In order to test it simply bridge from the starter battery terminal to the trigger terminal.

Try to crank and measure the voltage with one lead on the starter case and the other on the starter's battery terminal. Anything below 9.6v when cranking is a poor battery or connection. If below 9.6v, Check the voltage when cranking at the battery, if it's ok then the issue is a lead/connection.

 

[8ob]

Could be any of the above problems, before playing parts darts its worth testing out for some of the above. Could be a dead spot in the ignition switch.

The Kubota starters do suffer with solenoid issues, for any starter/alternator bits or complete starters you cant beat Woodautos
linky

Most Kubota starters are this type, the starter motor body gets bigger as engine size increases but generally they all seem to interchange.

They do suffer with the contacts burning.

 

[prepman]

I have a KX41-2b... only starter issue I had was a corroded crimp connector. It a had me stump. Refuse to start...nothing. + Good qualty battery make a big difference. Possible not your problem..
You had a need a manual..I have a lot of collect ....my writing all no good all present,

 

[aesmith]

Most Kubota starters are this type, the starter motor body gets bigger as engine size increases but generally they all seem to interchange.

That's the one, original part as per Kubota parts listing is 19269-63011, current replacement 19269-63013 which I think is 1.4kW vs the 1.2 original.

Just popped the cover off the solenoid housing and as before everything is free moving.

The contact surfaces could maybe benefit from a clean up. Would that really make it work perfectly most of the time, but sometimes not work at all? Will clean them up anyway as it can only help.

 

[aesmith]

I tried to measure voltage when cranking but my meter blinks off for a second and the engine starts before it recovers. Will try a different meter. But again would a low voltage while cranking stop it trying at all?

 

[Blobber]

They look a bit grubby, the shape of that contact plate looks odd in relation to the hole for the solenoid plunger bit, almost looks like its assembled wrong?

 

[sako243]

Would that really make it work perfectly most of the time, but sometimes not work at all? Will clean them up anyway as it can only help.

You may find there's just a bump or a bit of dirt which lines up with another bump etc., once in a while and that stops it making contact all the way around.

Handheld oscilloscopes are dirt cheap these days and will offer a far better view of what's happening to the voltage while cranking. You can probe various points along the wiring then to see if you're dropping volts anywhere. I have one of these and it's fine for this kind of job. Cheap enough it doesn't matter if I drop an engine onto it either. Better than lugging my £4.5k Keysight one about.

https://amzn.eu/d/cpGjKDP

Cheaper sources are available for the same thing but I posted that link for convenience.

 

[aesmith]

They look a bit grubby, the shape of that contact plate looks odd in relation to the hole for the solenoid plunger bit, almost looks like its assembled wrong?

You're right, compared to 8ob's photos it looks like connector for the start switch and the main stud are swapped round

 

[Blobber]

There is very little contact area on the plate by the looks of it?

 

[aesmith]

You're right, compared to 8ob's photos it looks like connector for the start switch and the main stud are swapped round

Looks like it's not just a missassembly that can be swapped back, the holes for the fittings aren't the same size. And even if I drilled it out, the plate would now be too far the other way.