B2400 Starting Problem

Pks · Apr 1, 2002

After putting nearly 60 hours on the meter while clearing land for new barn, my Kubota just died. It's the wierdest thing too. The engine starts and runs well, at any throttle position as long as I hold the key switch in the START postion. I can hear that the starter is spinning freely once the engine catches so I'm not running the engine by keeping the started engaged. But as soon as the key is placed in the RUN postion, the engine dies; just as if it were shut off!

I replaced the fuel & air filters. Fuel flows back into the filter easily and quickly. The tank is about 1/4 full. I next removed the injection pump solenoid and verified that it functioned correctly: In when key is in run position, Out when ignition is turned off.

Then I measured the voltage in the three wires going to the solenoid: White, Black, Red/Black. During the start sequence, the Red/Black gave 12 Volts and the White gave about 9 Volts. The Black was used as ground for both other wires.

It seems to me that somehow the solenoid is being told to move to the Stop position when the key is placed in the Run position. Even though the earlier test showed proper position.

I have not yet been able to identify why: bad key switch, bad connections, bad solenoid coil(s). Could water in the fuel do this? The fuel has stabilizer in it.

Anybody have any experience with this kind of problem?

EdKing · Apr 1, 2002

My guess would be either a bad key switch or bad connections. If the fuel solenoid was bad, you wold think it wouldn't run at all, same with water in the fuel.

Pks · Apr 1, 2002

That's basically what I was thinking. It's almost as if the machine is being told to shut down when the key is in the Run position. But the weird part is that when I tested the movement of the fuel solenoid, it went to the correct position when the key was put in the run position.

That's what makes me wonder if it could be the fault of the solenoid. The wiring diagram shows two coils: one that operates with power from the Starter, another that operates from the ignition key switch.

Sure would like some help with this problem.

EdKing · Apr 1, 2002

<font color=blue>The wiring diagram shows two coils: one that operates with power from the Starter, another that operates from the ignition key switch.</font color=blue>

With that type of setup, it could be the solenoid. You could disconnect the wires from both coils, and do a resistance check on them. I would imagine the resistance should be close to the same. If the one going to the ignition switch reads open, thats probably your problem.

hayden · Apr 1, 2002

Do you have the workshop manual?

Were your measurements made with the harness connected to the solenoid? Sounds like they were.

Try disconnecting the harness and measuring voltages. In the Run position, the R/B wire should show 12V, and it looks like the W will show zero. In the Start position the W should show 12V too.

For some reason that's not apparant to me there are two circuits to activate the solenoid, one in the run position and the other in the start position. The Run position (R/W wire) has a fuse. Could that be blown?

Last, the manual says the resistance between the R/B and B should be about 1.5 ohms, and the resistance between the W and B should be about 0.4 ohms.

Oh, I think I see why there are two circuits. The Start circuit is lower resistance and hence will power the solonoid more strongly. This gives it the jolt for the initial engergizing and activation. From there, the solonoid is already activated and the higher resistance circuit stays on to simply hold the solonoid in position. The lower power reduces power draw on the alternator and reduces heating in the solenoid wirings. It's really pretty clever.

I'd bet a quarter you have a blown 5A fuse for the "hold" circuit. If not, you could jumper 12V to the R/B terminal and I'll bet it will run fine. If not, the solenoid is shot.

Pks · Apr 2, 2002

Hayden,

I think you have hit the nail on the head. I had some suspicions about it but I'm happier to see that someone else (given my preliminary data) came to a similar conclusion.

It may take a day or two, but I'm going to re-run the tests and be far more careful about the combinations of settings and voltages.

As far as the fuse for the R/B wire is concerned; I checked the fuse block and that fuse was OK. But I'll revisit that question first. I have been moving a WHOLE LOT of dirt in preparation for our new barn and I wonder if the contacts in the circuit just got full of dirt and corroded. Our sandy soil has a high acid content so maybe some corrosion set in. Does your manual mention how many Amps are drawn on the White and R/B wires during Starting and Running? The would be most conclusive, I think.

Thanks for the help. I'll keep the thread up to date.

kubmech · Apr 2, 2002

Hayden broke the code, /w3tcompact/icons/clever.gif PKS when you checked the fuse did you just pull it out and look at it? Or did you check for power on both sides and/or fuse continuity. I have seen bad fuses that look good as well as the connector that the fuse plugs into broke and not allowing good contact.

Pks · Apr 8, 2002

This Saturday, I followed the instructions in the Service section of my shop manual. There were two tests for the fuel shutoff solenoid.

One test looked at the number of Ohms across each of the two resistor coils inside the solenoid. The Run circuit (the red lead) had an infinite amount of resistance, which, by the book, meant the solenoid failed the test.

The second used battery power directly from the battery terminals to each terminal on the solenoid pigtail. The Start circuit (white lead) worked like a charm. The Run circuit (red lead) failed. The plunger did not move at all.

I called my dealer and ordered a new $120 solenoid. Yikes /w3tcompact/icons/shocked.gif Oh well, without it, my earthmoving job won't get finished.

I'll post some photos of the earthmoving job when they get developed. I have been pleasantly surprised at how much this little tractor can do (given enough time). /w3tcompact/icons/smile.gif

hayden · Apr 8, 2002

Sounds like you nailed it - good job

Pks · Apr 19, 2002

Thanks for the help guys. If I would have flipped a few more pages in my Service Manual I would have found the Stop Solenoid tests.

After receiving the new solenoid, I popped it in there, tightened the two bolts and gave the starter a whirl. And wouldn't you know, that little tractor started right up like usual. And when I put the key into the RUN position, IT STAYED RUNNING. Ya-HOO!! /w3tcompact/icons/grin.gif/w3tcompact/icons/grin.gif

Now I can go back to the barn and level the dirt floor. I need to make it ready for the concrete that will someday get poured in there.

Thanks again.