Kubota B7100HST Won't Start

[CyberBill]

Hey - thanks for taking the time to read this, I'm having trouble getting a Kubota B7100HST to start.

I've got a video showing the status:

When I crank the engine it seems like its making compression, but the starter isn't giving it enough ooomph to get it going. Replaced the battery (using a known good car battery - also used jumper cables from a pickup), confirmed glow plugs have low resistance, took the fuel lines off of the injectors and confirmed that fuel dribbles out, put some diesel in and bled the system (as best as I can tell) - and really not any change. I get a tiny bit of 'smoke' coming out of the exhaust manifold - but I don't think its doing any combustion.

The tractor is a neighbor's - about two years ago they went to use it and it wouldn't start. They said if I could get it going I could use it whenever - so I took it up as a project! Unfortunately I don't know anything about tractors, never worked on a diesel, but know plenty about wrenching and have worked on some cars.

Next thing I'm going to try is to remove the fuel injectors (seems like it would be harder to remove the glow plugs - the intake manifold is in the way) and see if I can spin the engine a few times to blow out any crap from the cylinders. I also want to see if the starter will spin faster then. If nothing comes out, and it's still spinning slow, then I'm thinking it's the starter. We shot plenty of starter fluid in the intake filter housing without anything happening, so I also might try taking off the intake (up to the manifold) and making sure its clear and shooting starter fluid in more directly.

I'd love to hear some suggestions of things to try!

Thanks everyone!

 

[GeoHorn]

STOP ”SHOOTING” STARTER-FLUID in the intake! That’s a great way to seriously damage a diesel. Kubota specifically says don’t do it.

Ether/starting fluid can/will ignite BEFORE the piston gets to TDC and can bend a rod or worse.

 

[Dave_eng]

If you know nothing about diesels at least get the free workshop manual at this link.
WSM
I think you will also find an operators manual at the same location.
These old engines need a lot of glow plug pre heating time. Up to a minute. From your video I think you do not heat enough!
You may have already destroyed the engine using quick start.
Buy a cheap diesel engine compression gauge from amazon and remove the glow plugs to do the test.
If the compression is too low it will never run well and rarely start,
There is no crap in the cylinders so do not waste your efforts on that.
Post some photos of the top of the battery and also where the ground cable attaches to the tractor frame.
Since you have a multi meter study this DENSO troubleshooting guide which will let you know if bad connections are holding the starter back.
Dave

 

[Runs With Scissors]

 

[N3BP]

The issue is your batteries. A battery isn't considered fully charged unless it's around 12.6-12.7V. If the battery in the tractor is bad, it will draw from the good battery until it reaches equilibrium. I'd suggest fully charging the good battery, then hook it directly to the tractor cables without having the bad battery in the circuit.

 

[Lencho]

I also think your battery is the problem. Even with the extra battery you can see the voltage drop and the starter spins very slow. Can you get a vehicle close enough to jump start it?

 

[tsp159]

I also think your battery is the problem. Even with the extra battery you can see the voltage drop and the starter spins very slow. Can you get a vehicle close enough to jump start it?

A weak battery is bad, but poor connections can also make a starter slow. A good clean ground and connection to the starter are necessary. This tractor looks very clean (better than mine!) but you never know. Sometimes the cables can have internal damage causing poor current carrying.

These old engines need a lot of glow plug pre heating time. Up to a minute. From your video I think you do not heat enough!
You may have already destroyed the engine using quick start.

Louder for the people in the back of the room. Not enough glow plug? It'll never run. Give'r about 30-60 seconds? Pop right off. My B7100 sits for...a long time (it's not neglect, I swear!), but all they need is some plug.

The D-750 series engines have an aggressive pre-chamber to initialize the combustion. Starter fluid doesn't really do the trick for them.

 

[ve9aa]

Just a datapoint. My 23+ yr old TG1860 (700cc 3cyl diesel) wouldn't start on the hottest day of the year w/o glow plugs even when it was "relatively" new (@ 500hrs I got it). At 960 hrs, it's no better.

In the spring, when it's cool, the first few starts of the year sometimes I have to glow it 2 or 3 times if it's 30-40-50*F (0-10*C for us CDN's)

More heat, longer - - good battery connections.

 

[ve9aa]

p.s.- if the battery in the tractor is utter cr@p (you can't know w/o a load test) and your little starter/jumper battery is good, all you're doing by putting them in parallel is loading down both batteries. (the good battery in essence is trying to charge the bad battery with not much left over to do any amount of glowing and cranking)<<<---and boy is that cranking slow.....TOO SLOW

There are times when paralling 2 batteries will work in your favour, but if the one in the tractor is totally zonked, you'd be better off just using the one "known good" battery.

JMO

 

[Muskilunge]

does it have the decompression knob? Might help to see if it will spin faster with it pulled. My bet is with the rest, bad battery not helping.

 

[CyberBill]

If you know nothing about diesels at least get the free workshop manual at this link.

Dave

Thank you! I thought I had the whole WSM, but apparently I only had 'part 1' of 3! I'll review those as well.

 

[North Idaho Wolfman]

Don't make me drive over there and fix it, I'll do it!
HAHAHA...
Has it ever started good for you or is it a new acquire that you haven't gotten running yet?
Does it look like the engine has been opened up?
Tell tale signs are gasket sealer, scratched up bolt heads.

#1 Get a new battery that ones toast.
You can load test it just to make sure.
It will drag like that with a bad battery.
#2 Then if that does not yield a fast spin, then look very closely at both cables and connections.
If the look bad replace them, those cables are fairly cheap.
#3 Then if you still don't get good spin, remove the injectors and you should be able to easily spin the engine by hand, if you can't you have an internal issue, and need to go through the engine.
#4 If it does spin easily, try cranking it, still an easy spin fast or does it sound labored?
I would invest in a new starter.

 

[CyberBill]

Thank you all so much!

Seems like a lot of consensus on two points: Bad battery, more glow plugs!

On the battery, I picked up a new replacement battery yesterday and will get it installed today. I've also let my jumper battery fill up on the charger overnight, so it should be good. Before hooking it up I will clean off the terminals and the starter wire as well. For the video I had placed the bad battery in parallel, but for testing we had it removed and were jumping straight off of a running pickup - so we should have had 14V and plenty of juice.

I will also hold down the glow plug for a full minute before the next test... and I'll hold back on my starter fluid usage.

If the starter is still going slow with extra battery on it, I think the next thing on my list is to determine if the issue is a bad starter or something in the engine causing excess drag. Since this tractor does not have a decompression knob, I want to remove either the plugs or the injectors. I could also remove the starter and inspect it to see if it looks worn out.

I'll report back this evening and see if I have any luck with it.

 

[ve9aa]

"...If the starter is still going slow with extra battery on it, I think the next thing ..."

I'll report back this evening and see if I have any luck with it.

If your original (in the tractor) is NFG, then (imo) you are doing yourself a small disservice by putting another in parallel. It's just going to drag the voltage down, making the starter roll slower. You can use your voltmeter to watch this before you even touch the starter.

If it's just a little low, or a little soft,(capacity of amps-wise, not voltage-wise) then by all means parallel it up to a known good one.

 

[CyberBill]

If your original (in the tractor) is NFG, then (imo) you are doing yourself a small disservice by putting another in parallel. It's just going to drag the voltage down, making the starter roll slower. You can use your voltmeter to watch this before you even touch the starter.

If it's just a little low, or a little soft,(capacity of amps-wise, not voltage-wise) then by all means parallel it up to a known good one.

This would be a brand new battery + a good jumper battery. The old dead battery was returned for the core charge.

 

[ve9aa]

This would be a brand new battery + a good jumper battery. The old dead battery was returned for the core charge.

ahhhh-perfect. I misinterpreted your message.

Good luck.

I'll check back in later and hopefully have a smile that I'll read you got it going and now have a free tractor to use.

 

[number two]

Interesting post!
What is the correct battery group number for this tractor?
I saw a B7100HST last year that had what looked like a lawn mower battery.
Thanks!

 

[N3BP]

Interesting post!
What is the correct battery group number for this tractor?
I saw a B7100HST last year that had what looked like a lawn mower battery.
Thanks!

Group 51R, which are marginal performers on a diesel engine due to their size limitations.

 

[CyberBill]

ITS ALIVE!!

Thanks everyone for your helpful advice.

I removed the main positive wire from the starter & battery, cleaned it and the 'jumper' wire that goes from the solenoid to the main starter. Then removed the ground wire from behind the control panel and cleaned it as well. I used a brillo pad to scuff all of the electrical connections, sprayed them with electrical contact cleaner, made them nice and shiny. Honestly they weren't that bad to begin with and (to me) looked like they had been replaced before.

The battery was replaced with a brand new one ($250!!), and I also used another battery in parallel for good measure. I double checked all the fuel lines and positions of the control levers to make sure it was in neutral and getting fuel. I held down the glow plug for a solid minute. And then it started right up instantly!!

Here's a video of starting up (after I spent a few minutes driving around my neighbors yard testing everything out):

 

[N3BP]

Glad to see (and hear) it starting properly. Have fun with it!