Kubota B7500 wont start

kevinj

Member

Equipment
L3940hstc - B7500hst - BX1860 - Farmall 560D - Farmall M
Jun 4, 2018
89
2
8
Michigan
Yes, this model B7500 has a spring return to the starting position.
I have a B7500 since new, it does not spring return to run.

It snaps out and stays, You have to push it back in over the snap point to start it.
 

GeoHorn

Well-known member
Lifetime Member

Equipment
M4700DT, LA1002FEL, Ferguson5-8B Compactor-Roller, 10KDumpTrailer, RTV-X900
May 18, 2018
2,508
703
113
Texas
Just to elaborate on the “NO STARTER FLUID” warnings:

Starter Fluid or “Ether” is intended for SPARK-IGNITION Four-Cycle engines... NOT COMPRESSION ignition engines....and not 2-cycle engines.

Why? Because a spark-ignition engine has a specific MOMENT that the fuel is ignited via electrical-control of that timed event. But a compression-ignition engine (such as diesel) times the ignition event by injecting the fuel into the hot/compressed air which instantly ignites the fuel. Spraying fuel (starter-fluid/ether) into the intakes completely ignores the correctly timed ignition-event.

Spraying a fuel which is easily-ignited at low temps (starter-fluid/ether) into the intakes of an engine which will compress that mixture PRIOR to the piston reaching Top-Dead-Center will result in IGNITION occurring prior to the correctly-timed moment. If you’re lucky that will be while the intake valve is still unseated which will relieve the intense pressures of that event.
But it is highly likely that the fuel (ether, perhaps now mixed with diesel) will ignite PRIOR to TDC and will produce more energy than the engine can physically endure without serious damage.
This can result in blown-pistons, bent connecting rods, etc etc.

(Starter fluids should also not be used with 2-cycle spark-ignition engines because the fuel/air mixture normally has access to the crankcase for lubrication of the lower engine-unit purposes. A portion of the ether can remain in the crankcase and when the main fuel-charge is ignited.... so may be the lower crankcase...which is not designed to contain combustion-pressures. )
 

JerryMT

Member

Equipment
Kubota M4500, NH TD95D,Ford 4610
Jun 17, 2017
234
7
18
The Palouse - North Idaho
Just to elaborate on the “NO STARTER FLUID” warnings:

Starter Fluid or “Ether” is intended for SPARK-IGNITION Four-Cycle engines... NOT COMPRESSION ignition engines....and not 2-cycle engines.

Why? Because a spark-ignition engine has a specific MOMENT that the fuel is ignited via electrical-control of that timed event. But a compression-ignition engine (such as diesel) times the ignition event by injecting the fuel into the hot/compressed air which instantly ignites the fuel. Spraying fuel (starter-fluid/ether) into the intakes completely ignores the correctly timed ignition-event.

Spraying a fuel which is easily-ignited at low temps (starter-fluid/ether) into the intakes of an engine which will compress that mixture PRIOR to the piston reaching Top-Dead-Center will result in IGNITION occurring prior to the correctly-timed moment. If you’re lucky that will be while the intake valve is still unseated which will relieve the intense pressures of that event.
But it is highly likely that the fuel (ether, perhaps now mixed with diesel) will ignite PRIOR to TDC and will produce more energy than the engine can physically endure without serious damage.
This can result in blown-pistons, bent connecting rods, etc etc.

(Starter fluids should also not be used with 2-cycle spark-ignition engines because the fuel/air mixture normally has access to the crankcase for lubrication of the lower engine-unit purposes. A portion of the ether can remain in the crankcase and when the main fuel-charge is ignited.... so may be the lower crankcase...which is not designed to contain combustion-pressures. )
]
Well starter fluid (ether) was used as a cold starting aid on lots of the old diesels and it was factory installed. I've seen plenty of CATs and TD's, JD Tractors, etc that had a place where a canister of starting fluid was mounted on the fire wall and there was plumbing to carry the ether to the intake manifold. I don't know how the operator triggered it but none the less it was used on diesels in the 40', 50's and the 60's. When intake heaters like the MF heated grid and the Ford Thermostart came along, you could damage the engine by squirting ether in to the intake manifold while operating the heater, especially the Thermostart which has an open flame. So there were warnings about not using ether with these systems.
The old system was designed to give a wiff of ether to aid in cold starting but now a days impatient people spray a half a can and end up damaging the piston lands and rings, etc as George points out . Ether never was a cure for a worn diesel engine with low compression that was hard to start. I agree with George. It should not be used on the modern diesel engines especially those with intake heat starting aids.
 
Last edited:

GeoHorn

Well-known member
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Equipment
M4700DT, LA1002FEL, Ferguson5-8B Compactor-Roller, 10KDumpTrailer, RTV-X900
May 18, 2018
2,508
703
113
Texas
Well...I”m sure Jerry means well....but those comments only apply to engines which Approve it....and I worry about noobies who may take those older designs and apply them to their own machines.

I believe it’s safer to say that IF YOUR machine doesn’t have a built-in starting-fluid provision Approved by the manufacturer.... then Don’t use Starting Fluid.
Read your Kubota Owners Manual. It likely says what mine says:
0A26CC4A-A265-4CEB-A626-FA0BB6041126.jpeg
 

CornGold3

New member

Equipment
Kubota B7500
May 27, 2021
17
0
1
Arkansas
Hello JerryMT,

How can I determine which shop manual to download?
How do I know which engine I have?

Please advise, thanks!
Hello everyone, I removed the injectors and performed a newbie compression check on all 3 cylinders from the fan back toward the fuel tank 1,2.,3. There was 120 psi on #1cylinder and 60 psi on both cylinders #2&#3! Any suggestions at this point?
 

JerryMT

Member

Equipment
Kubota M4500, NH TD95D,Ford 4610
Jun 17, 2017
234
7
18
The Palouse - North Idaho
Hello everyone, I removed the injectors and performed a newbie compression check on all 3 cylinders from the fan back toward the fuel tank 1,2.,3. There was 120 psi on #1cylinder and 60 psi on both cylinders #2&#3! Any suggestions at this point?
What's a "newbie compression check....."?

Those numbers are very low. Generally speaking, the numbers for diesels should be above 350 psig. The two low adjacent cylinders imply a blown head gasket between #2 and #3 cylinders. Did you put some motor oil in each cylinder and conduct a " wet" compression test? You should do that. If the pressure increases in the wet test then rings are bad. If there is no change, it could be bad valves, cracked or burned through piston crown. How many hours on this machine?
 

CornGold3

New member

Equipment
Kubota B7500
May 27, 2021
17
0
1
Arkansas
What's a "newbie compression check....."?

Those numbers are very low. Generally speaking, the numbers for diesels should be above 350 psig. The two low adjacent cylinders imply a blown head gasket between #2 and #3 cylinders. Did you put some motor oil in each cylinder and conduct a " wet" compression test? You should do that. If the pressure increases in the wet test then rings are bad. If there is no change, it could be bad valves, cracked or burned through piston crown. How many hours on this machine?
A "newbie compression check" implies, I may or may not have done it just right!! :)

I put some oil in it but in an attempt to start it and it did act like it wanted to start. I will perform the wet compression test as you have described and let you know what I find out. Oh by the way, I used a compression tester that has the rubber tip so I know some of the compression escaped passed the guage. I don't have the tester that you screw into the cylinder.
 

kevinj

Member

Equipment
L3940hstc - B7500hst - BX1860 - Farmall 560D - Farmall M
Jun 4, 2018
89
2
8
Michigan
A "newbie compression check" implies, I may or may not have done it just right!! :)

I put some oil in it but in an attempt to start it and it did act like it wanted to start. I will perform the wet compression test as you have described and let you know what I find out. Oh by the way, I used a compression tester that has the rubber tip so I know some of the compression escaped passed the guage. I don't have the tester that you screw into the cylinder.
You need a diesel compression tester, it must screw in as you never hold against 400 or so psi.

Harbor freight has some pretty cheap.
 

drewzee87t

Active member

Equipment
B2910 HST, Modern RC, Gannon Earthcavator, Frontier 1150 Tiller, Woods RM306
May 20, 2016
118
31
28
misery
You will also need the adaptors as none of the HF fittings will fit anything that doesn't say ford or chevy and even that is debatable. It took me forever and searching here to find the glow plug adaptor and then to also find the paintball air gun adaptor. Even the injector adaptors from HF won't fit as the injectors are recessed a bit into the head.

Sounds like you have my old B7500. I sold it to a very nice tractor recycle/junker in Arkansas with 1625 or so hours and very low compression :)
 

CornGold3

New member

Equipment
Kubota B7500
May 27, 2021
17
0
1
Arkansas
You need a diesel compression tester, it must screw in as you never hold against 400 or so psi.

Harbor freight has some pretty cheap.
Ok, thanks Kevinj, I purchase the one I have from HF, but the other one with all of the different attachments was $120 and I passed on it, so do you think that's the one I will need in order to get an accurate assessment of the compression(can you tell I'm waffling?).
 

CornGold3

New member

Equipment
Kubota B7500
May 27, 2021
17
0
1
Arkansas
Get yourself a diesel compression test kit with the adapter that fits the glow plug hole. Make sure the battery is fully charged.

Remove the glow plugs wires and then the glow plug. Remove them all to make it easy on the starter. Install the compression tester adapter in the first glow plug hole. Attach the hose with the compression gauge to the adapter. Crank the starter until the pressure does not increase any further and record the "dry" compression pressure reading. (Do not engage the starter for more than 30 seconds). Remove the gauge and put a couple of table spoons of engine oil in the glow plug hole, reconnect the gauge and repeat the test, recording the "wet " compression pressure. Do that on each cylinder and come back here with the numbers.

In general, your pressures should not be lower that 350-375 psi. Higher is better. They should not vary greatly ~+/- 10%. ( The WSM for your model will give you better numbers as these are based on my general experience.) If you see that that the wet pressures are significantly higher than the dry pressure this would indicate worn rings. If you have a cylinder that is low and does not improve with adding oil that indicates a leaking valve and it could be burned or out of adjustment.
Sorry for the delay in response, somewhere in the other post I missed your post about the compression check. I will try to perform it but I don't know that I have the tooling to remove the glow plugs, I will verify. It's been raining alot and the tractor is sitting outside, so as soon as the rain subsides, I will get started again. As always, thanks for your help.