Kubota BX2670 cranks but won't start, fuel system seems fine

CasualObserver · Apr 14, 2022

Tractor was running perfectly, no issues at all. Used it for about 5 minutes, left it idling a couple minutes. Came back and it was off with clicking still going from fuel pump. Tried to start it. Turns over fine but never catches.

I replaced the fuel filter under the floor pan first. No go. Checked fuel flow coming from tank - full heavy stream before the first filter - so fuel tank is not blocked. Took fuel line off after the second fuel filter right before it goes into the engine. It pumped a over cup of fuel into a bottle in about 15 seconds so fuel flow seems good to engine.

After I try to start it the stop solenoid arm moves when the key is turned back to the off position. 9 seconds later the relay timer kicks in and the stop solenoid arm moves back to the normal position. So that appears to be functioning correctly.

Does not appear to be a seat / PTO interlock since those prevent the engine from cranking at all when I tested them.

Any other ideas on what I should check next?

Thanks!

Roadworthy · Apr 14, 2022

Usually safety switches will prevent the engine from turning over at all so I don't think it's a safety switch. If you've followed the bleeding procedure after checking fuel flow consider checking the air supply - both the filter and ensuring a clear path from there to the intake manifold.

CasualObserver · Apr 14, 2022

Bled the fuel lines by loosening the bleeder bolt that goes into the engine until it pumped out fuel in steady stream no bubbles.

Removed air filter, very clean. Have had mice in tractor air filters in the past, no signs of intrusion for this one. Removed air hose after air filter going to engine. Cranked and right away it developed enough suction from engine to suction hose to my hand and start collapsing the hose.

JWR · Apr 14, 2022

Well, it only takes 2 things for a diesel to run -- fuel and compression. You are missing one of the two. Compression would not suddenly disappear or certainly not in all cylinders at once even if a ring broke or whatever. So your problem is fuel.

You could have injector problems but not all 3 at once.

I gather from your description of bleeding that it was after the fuel pump and before the injection pump. So... I think you have an injection pump problem of some sort.

They can be pretty finnaky and will not squirt water at high pressure through the injectors even to clear itself. At this point there is the dilemma of whether to debug the thing further or seek professional diesel medical assistance... I would loosen the lines at your injectors and see if you get flow at all 3 (or at all.) That will tell you a LOT about the problem. If you are way luckier than I ever am, you will get some flow at the injector lines and maybe it will pump long enough and full flowing enough to clear the thing. If you are that lucky, run it long enough to get flow at all 3 lines. Impurities, a tiny bit of water, who knows. If you get NO flow at the injectors you have no choice but to decide who pulls the injection pump and repairs, cleans or replaces it. Not cheap...

Good luck and hope you find one of the less severe problems.

Ed ke6bnl · Apr 14, 2022

I just picked up a B7800 sitting 6 years, put fuel in started right up, 5 minutes later died woul not start. Pulled hose from filter water and oil came out then had to start with the dirty word ether. Has been running great since.

CasualObserver · Apr 15, 2022

After reading the replies from "JWR" and "Ed ke6bnl" I decided to replace the filter next to the engine also even though it appeared to have good flow through it. I actually used the lift pump to pump all of the fuel out of the tank until it was dry. I then replaced the fuel filter and filtered the 5.5 gallons of diesel I took out through a "Mr. Funnel AF3CB Fuel Filter" that I use and put it back in the tank. Seems to do a good job removing any water and other dirt from the fuel.

Once I did that I tried cranking it and got some black smoke from it trying to start. Much better than before when I had no smoke. I then cracked open the fuel lines after the injector pump and tested to see if I was getting fuel there as "JWR" suggested. Two of the lines had fuel coming out pretty quickly. the third one did not. I cranked a little longer and had fuel at all three lines. I then tightened them up and tried starting it again. It started really rough and died once. Started again rough and then cleared up after about 10 seconds. Appears to be running good now.

Thanks for the help! Appreciate it.

JWR · Apr 15, 2022

Great to hear ! Glad it was nothing serious. I think it likely that you picked up some water or other impurity that the injection pump did not tolerate and opening the high pressure injector lines allowed it to "clear it's throat." You are lucky that is all it took.