1997 NH 3930 - No Start

kubotaorange76 · Aug 20, 2021

Ran fine when parked about 5-6 months ago after Dad tilled his Garden. Visited property with him about 5 weeks ago (right before he passed), tried to start to no avail. Came back a week ago with more time to spend on cutting roads, I inherited a little problem looks like as I still couldn't get it to start. Here is what I tried (in the dark)

Fuel tank is full of clean fuel, topped off to be sure
Filters have fuel, i pulled plugs on bottom to verify and had steady flow of clean fuel, I did not bleed filters from the top because I was unaware of that procedure until doing some reading on here this morning.

I did verify fuel is flowing to pump by removing bleeder screw, and pump is turning internally. But fuel did not spray out of bleeder when turned over, kind of bubbled/drizzled out, and was not running out of pump when not turning over.

I pulled the electric shut off solenoid and verified it moved when key is turned. Tried tapping with hammer while on pump in case it was sticking. Manual shut off lever on top of pump is pushed towards the front of the engine as it should be and springs back that direction when pulled as it should.

Cannot get fuel spray to injector lines. Cracked line(s) at pump and no bubbles, no spray, same at injectors(obviously)
IS there something I am missing?

Tractor is 3 hours away, so I'd like to come prepared. Seems odd it ran fine, was shut off and now wont start. No fuel leaks were observed anywhere so I don't know how it would have lost prime. Tractor has apprx 800 hrs.

With the fuel supply(or is it return?) line off the side of the pump(this is how i verified pump is turning) after turning over for a short while it does briefly spray a tiny bit of fuel out of that line when you let off the ignition key, not sure what that means. Fuel ran steady out of the pump with this cover plate removed, I had to shut off fuel at tank to get it to stop.

Thinking more about it after typing all of this out, I should probably pull the filters and check that first huh? Maybe they are nearly clogged and not allowing enough pressure/flow to fully bleed the pump?

I dont know when the last time the filters were changed, its def been over 5 years, I remember maybe 10-12 years ago it got algae in the fuel and had to have injectors and tank & sock cleaned and new filters.

kubotaorange76 · Aug 20, 2021

Just learned there is an inlet screen on the CAV pump thanks to this forum. Im going to go down there armed with new fuel filters and an inlet screen filter. This tractor sits under a lean to and gets used only a handful of times per year, so Im guessing water/rust from filters plugged up inlet screen. As this happened to the Kubota 8540 about 2 years ago(inlet screen got plugged with rust).

JC-jetro · Aug 20, 2021

i would loosen the nut that holds fuel line to the injector just a bit, crank the engine just to see if you get a bit of air and fuel coming out. This is to bleed the air right up to the injector. Injector pump can pump liquid but not air. Air is compressible but not fuel, so if you have air it keeps getting squeezed by pulsating action of the injector pump but would not move fuel. That might help to get your rig started. Be careful not to damage the nut or strip the threads.

JC,

PS. RIP to your dad. I hope he is in a better place.

Seven Gables · Aug 20, 2021

kubotaorange76 said:
Just learned there is an inlet screen on the CAV pump thanks to this forum. Im going to go down there armed with new fuel filters and an inlet screen filter. This tractor sits under a lean to and gets used only a handful of times per year, so Im guessing water/rust from filters plugged up inlet screen. As this happened to the Kubota 8540 about 2 years ago(inlet screen got plugged with rust).

I’d say very much on the right track with your plan. Change filters , New screen and make sure air is correctly bled and should run. As a owner of many of that vintage tractor over the years I have much faith in them especially with that low of hours

Jerry/MT · Aug 22, 2021

kubotaorange76 said:
Ran fine when parked about 5-6 months ago after Dad tilled his Garden. Visited property with him about 5 weeks ago (right before he passed), tried to start to no avail. Came back a week ago with more time to spend on cutting roads, I inherited a little problem looks like as I still couldn't get it to start. Here is what I tried (in the dark)

Fuel tank is full of clean fuel, topped off to be sure
Filters have fuel, i pulled plugs on bottom to verify and had steady flow of clean fuel, I did not bleed filters from the top because I was unaware of that procedure until doing some reading on here this morning.

I did verify fuel is flowing to pump by removing bleeder screw, and pump is turning internally. But fuel did not spray out of bleeder when turned over, kind of bubbled/drizzled out, and was not running out of pump when not turning over.

I pulled the electric shut off solenoid and verified it moved when key is turned. Tried tapping with hammer while on pump in case it was sticking. Manual shut off lever on top of pump is pushed towards the front of the engine as it should be and springs back that direction when pulled as it should.

Cannot get fuel spray to injector lines. Cracked line(s) at pump and no bubbles, no spray, same at injectors(obviously)
IS there something I am missing?

Tractor is 3 hours away, so I'd like to come prepared. Seems odd it ran fine, was shut off and now wont start. No fuel leaks were observed anywhere so I don't know how it would have lost prime. Tractor has apprx 800 hrs.

With the fuel supply(or is it return?) line off the side of the pump(this is how i verified pump is turning) after turning over for a short while it does briefly spray a tiny bit of fuel out of that line when you let off the ignition key, not sure what that means. Fuel ran steady out of the pump with this cover plate removed, I had to shut off fuel at tank to get it to stop.

Thinking more about it after typing all of this out, I should probably pull the filters and check that first huh? Maybe they are nearly clogged and not allowing enough pressure/flow to fully bleed the pump?

I dont know when the last time the filters were changed, its def been over 5 years, I remember maybe 10-12 years ago it got algae in the fuel and had to have injectors and tank & sock cleaned and new filters.

But fuel did not spray out of bleeder when turned over, kind of bubbled/drizzled out, and was not running out of pump when not turning over.
It should shoot fuel over the front tire when cranking. This says that you don't have adequate fuel delivery to the pump. make sure you change the fuel filter and properly bleed the fuel delivery system.
When properly bled, fuel should flow out of the line from the filter to the Injector Pump (IP) like a cow peein' on a flat rock!

jaxs · Aug 22, 2021

Jerry/MT said:
But fuel did not spray out of bleeder when turned over, kind of bubbled/drizzled out, and was not running out of pump when not turning over.
It should shoot fuel over the front tire when cranking. This says that you don't have adequate fuel delivery to the pump. make sure you change the fuel filter and properly bleed the fuel delivery system.
When properly bled, fuel should flow out of the line from the filter to the Injector Pump (IP) like a cow peein' on a flat rock!

So don't overlook taking a change of clothes when you go.

JC-jetro · Aug 23, 2021

Again folks, air is compressible and diesel is not. When you crack open the injector retaining nut at the injector, it will only fizzles the air out plus some fuel at the same time (assuming if there is air in the line). The high pressure at the injector is made when small volume of fuel is pumped by reciprocating action of tiny piston/cam lobe against a very stiff injector spring. The stiffness of the injector is what is behind the high pressure. injector pump only squirts pulses of fuel if the pump discharge line is open.

kubotaorange76 · Oct 22, 2021

Sorry for the delay guys, I thought i had email notifications turned on but appears i did not. Ive been down twice now and here is where I am at.

So i got the tank & everything cleaned out & filled to the brim, got the drain valve un clogged(someone had removed the sock) and new filters installed. Filters bled till clean airless fuel came out the top. Now down to the pump i loosened the bleeder screw while turning over and got a ton of fuel coming out, left it cracked until all the air was purged and was sure to close bleeder while still turning engine over.

With a good Battery charger, and utilizing a gas soaked rag over intake for extra rpm I tried and tried and tried and could not get anything to come out of the lines, removed the lines from the pump head and nothing is coming out. It was wet with fuel but nothin flowing. I verified the pump fuel shut off is working and free of debris inside. I have bled this style injection system before and I know what ive done is enough based on previous experiences.

The fuel that came out was very very varnished(yellow & smelly) and there was very light surface rust inside the filters and injection pump. Is there something i can remove/clean in the pump head that might be sticking? It seems like this pump is stuck and not pumping fuel. I tried some light taps with a hammer in various places as well as let it sit overnight with injection lines loose to see if gravity would do it's job and still nothing.

Thanks for any suggestions you might be able to provide