Kubota B7500 Continued

A couple weeks ago I posted on here about some fuel issues with my Dads B7500. It was stuttering after about an hour of use, to the point where he could only limp it back to the shop and shut it off until it cooled down. After doing seasonal service the problem started happening after a few minutes of running. Many of you suggested lack of fuel flow to the IP, and we tried removing the gas cap but that didn't help. Today he went to start it and it wouldn't start at all.

So, here's what I know:
-Good fuel flow to at least the filter
-Filter was replaced less than a month ago
-All fluids changed out/seasonal service less than a month ago

Where do we go from here? Should I suspect IP? He's ordered a new gas cap but it didn't even start w/ the cap all the way off so I doubt that will fix the issue.

Not sure where you're located, but I know here in northern NY we had a significant problem with fuel this winter. Several big fuel places got bad batches of diesel and when cold weather hit there was a huge glut of problems with fuel gelling, to the point where some places were changing filters every day in order to get their equipment to run. If you're still getting cold weather and if for some reason your fuel is still old stock (for instance, you got a bad batch in the fall and don't go through enough to use it up over the winter) it's possible you've got a gelling problem. At a minimum, change out the filter and see where that gets you, and draining and refilling with known good, fresh fuel might also be a good idea.

Could be a bad fuel filter. Occasionally, I've seen new ones that just don't pass the fuel. Also check for water in your fuel. It can
come from condensation in the fuel tank if it was not full during the damp season or from a bad fuel delivery. Good luck!

I'm assuming you've bled it properly following service? I've not worked on a kubota that small. Later ones have self bleeding knob or a priming pump.

-How clean was everything during filter service? I've found debris in the fuel inlet to injection pumps before that could have only entered during filter change.

-Can't recall if the 7500 is old enough to have a manual shut off / emergency shut off. Sometimes find the pump has this function and is shut off almost all the way.

-If main shut off is a power to run fuel solenoid, may have bad solenoid or valve.

Yes of course rule out water in the pump too, but that should have been noticed during filter change. It won't run if the injector lines are full of water.

To my knowledge there is no fuel pump. I may be wrong, but I could only see a line going straight from the tank to the filter then to the injector.

The filter looked ok. There was a bit of mess in the plastic cover we couldn't get out, but it was stuck pretty good.

We're in Eastern NC so it can get humid. I'll have my dad check for water in the tank. Maybe we should drain the entire system?

If it is cold weather just take one of those small torches and warm the filter up if that changes things you have a fuel problem whether gelled or froze, might even be a bit of dirt and warm fuel flows through better. If no change check for fuel out of the low pressure pump, or try repriming with the air out better. My welder has a little Kubota engine. It is tough to get all the air out so it will run right.

Are you getting fuel to the injectors? As in fuel comes out when a line is cracked loose when cranking?

If no, check the kill solenoid, or whatever shuts it down. If that checks out, and there is fuel available at the pump, something is up with the injection pump.


If fuel to injectors, is there white smoke (fuel vapor) when cranking?

If no, there may still be air in the system, the injectors are clogged, pump not making pressure.


If white smoke, but no start, glow plugs or intake heater working? Compression? Pump timing?

Will the engine fire if you spray a whif of quick start
into the air intake?

Dad said it smoked when he tried to start it this morning. I don't know why any of those other things would've been off. I don't think it has glow plugs. The tractor hasn't given us any other trouble so I'd be surprised if compression was the issue. Seems to have good flow up to the filter for fuel. I dont know about after the filter.

It does have glow plugs and they are absolutely necessary for the older B 7500. easy to take a test light and see if you are getting current to the glow plug strip but that does not mean that the plug it self is not bad.

Yep, i have one.(bought new)

Glow plugs needed year round. 5 seconds in the summer & 10 to 15 in the winter.

Sounds like maybe ya need a manual for it.

Don't know if has a shut off solenoid or not, but the one on my BX was sticking causing the no start problem

"Dad said it smoked when he tried to start it this morning. I don't know why any of those other things would've been off. I don't think it has glow plugs. The tractor hasn't given us any other trouble so I'd be surprised if compression was the issue. Seems to have good flow up to the filter for fuel. I dont know about after the filter."
That sounds like glow plugs

But, you stated ran for an hour limped back restarted after an hour after it cooled down
Not a glow plug related issue although have to agree they start much better using the glow plugs.

Now As Steve Questioned
"Are you getting fuel to the injectors?"
If this a fuel problem crack one of the fittings,(while cranking) I can't remember if mine had a bled screw? but if you have good flow with out air. It should run, If it doesn't then there is something else going on.
Like Steve@Advance posted, follow his line of diagnosis, try to answer his questions.
My personal experience is that I had B7500 for 17 years and wish I still had it, but sold it to get a bigger tractor.
I had aftermarket fuel filter issues returned to kubota brand solved it.
Fuel cap vent plugged clean the vent solved.
They really don't like dirty air cleaners dramatic smoke and power loss. Make sure you check or change both.
Never had a glow plug fail but originally used to think I would use them up if I used them all the time. Got over that much easier on engine to use regularly.
Had a wire connection corrode for the fuel solenoid cleaned replaced connector -solved. Also used several other pieces of equipment that had Kubota engines the largest issue of all was failure of the fuel solenoid but mostly because of wiring problems.
Only real complaint was that I would have to blow the radiator out couple times when mowing alot. just had to learn to keep it clean.
Ken Macfarlane's post
I'm assuming you've bled it properly following service?
Answer some of these questions and I'll bet someone on here will point you to a solution. They've helped me solve a few.
The more information you can give the better the answers will be.