Random Hard Starts

jp2code · Jun 14, 2020

I posted this on another forum, but it got only one reply.

I have a Kubota L4400DT.

The engine turns over fine and the battery is nice and strong. Sometimes the engine starts immediately, but other times I can crank and crank and it will not start at all.

A couple of possible clues:

When it doesn't crank, after a long {burr-rur-rur-rur-rur} of the engine, sometimes I let off the key and it sounds kind of like the engine turns backward just a bit. Maybe it's just the compression letting off and turning the engine back a quarter turn or so.
As I turn the key, sometimes I hear a single relay click but other times I hear several clicks. The sound is like one or more relays is energizing and then loses contact. I think my non-starts occur typically when I hear several relay clicks. Like I said, it is intermittent.

How would I go about troubleshooting this?

The one response I got on another forum was to replace the fuel cutoff solenoid. I did a little research on their forum, and it seems a faulty fuel cutoff solenoid only prevents the engine from shutting off. Maybe that one guy replying didn't know what he was talking about. But then again, maybe he's enlightened where I am not!

Note: Last fall, my L4400 would not crank every time, and it left me stranded miles from home on one occasion. I suspected the "under-seat safety switch" and the "neutral gear position safety switch". I was able to remove the "neutral gear position" switch and test it, but the Delphi connector on the "seat safety switch" was crushed and I could not get it apart without destroying it. I sent it to the Kubota dealership to get it fixed, and the bill came to $1475. They said it took lots of man-hours to diagnose the problem because it was intermittent, it turned out to be the "seat switch". I'd rather not send my tractor back to the Kubota dealership until after I have won the lottery.

Roadworthy · Jun 14, 2020

If your engine turns over that's a clue that all the safeties are satisfied. It's a diesel so if you have fuel, air, and compression it should run - oh, yes, the glow plugs. Check your air filter and passages so we can eliminate that one. I'm just guessing you have compression because the non starting is a "sometimes" thing. If you've been around tractors awhile you already know about glow plugs. Besides, summer is coming on and you probably don't need them that badly in Texas. That leaves fuel. I think (do not know for sure) the Kubota solenoid is a normally open valve which shuts off the fuel briefly when you turn off the ignition. What happens if it sticks in that closed position and doesn't reopen? That may be farfetched but it's food for thought. You could try bypassing the solenoid to have fuel all the time. You could put a little valve in line to turn off fuel flow to kill the engine. That was just another thought. It would be too simple to have your BX with the same solenoid as the L. Then you could just swap them to see if the problem follows the solenoid. Of course if your problem is computer related (if you have a computer on that tractor) that would open a fresh can of worms. This is just blue sky stuff. Perhaps something will click.

jp2code · Jun 15, 2020

I don't think either of my tractors use computers. I've owned the BX since 2008 and the L4400 since 2014. I've got the parts manuals in PDF, and neither have shown that. But, I can't seem to find this fuel shutoff solenoid in the parts diagrams either. If I knew where it was on the tractor, it would make debugging it easier. Would it be mounted close to the injectors or under the instrument panel?

thepumpguysc · Jun 19, 2020

The s/o sol. will be very close to the inj. pump.. it痴 either up by the throttle or screwed into the side of the block, directly inline w the inj. pump..
That clicking u hear is either the relays clicking or the actual sol. itself engaging and disengaging..
Have a look around the inj. pump area.. you値l find it..
Good luck

number two · Jun 19, 2020

The Kubota Owning/Operating forum would be a great place to post this problem for additional imput.

Good Luck!

jp2code · Aug 7, 2020

So I found and replaced the fuel shutoff solenoid. It took a long time for the part to get here.

Apparently, that $200 part was not the problem. The tractor is still difficult to crank.