BX23 cranks briskly but no start for 20 seconds

[RRTREU]

I have a BX23 that is about a dozen years old. It has always started quickly until a couple weeks back.

Now it cranks as fast as ever but with no hint of starting for 20-30 seconds. Then it starts fine and runs perfectly. There is no period of half catching and failing. It goes straight from unproductive cranking to giving a little cough of soot and running smoothly.

I replaced the Fuel Shutdown Solenoid but it made no difference. Then I tried an experiment that left me puzzled. When I remove the solenoid I can see a little lever it pushes to shut off fuel and kill the engine. I can turn the ignition with no solenoid in place and the tractor starts promptly. I can kill the engine by pushing in the lever within the injector pump and the tractor stops just as it would if the solenoid piston had been there to extend.

As soon as I put the solenoid back on the 30 seconds of unproductive cranking returns. I went back and forth, trying with the solenoid removed and then with it installed. Every time the solenoid was installed, the problem returned. Every time it was removed starting was perfect.

Help

 

[100 td]

Sticky solenoid or bad connection to it somewhere, so there is not quite enough voltage getting to it (voltage drop) and with 30 seconds of cranking it vibrates into action. Not sure if yours has a timer/OPC controller, I would suspect a bad/poor electrical connection somewhere. Rats/chewed wiring.

 

[Grouse Feathers]

Maybe the linkage is sticking. Try moving the throttle to full and back to minimum and then starting. If moving the throttle works and the tractor starts right up, clean and lubricate the solenoid and fuel shutoff linkage.

 

[twomany]

Other references to similar issues.
http://www.tractorbynet.com/forums/kubota-owning-operating/121576-bx23-solenoid-location.html

 

[thebicman]

I don't have that model nor am I sure this is correct. Are you positive the which way the solenoid works? As in is it normally on or off.

 

[North Idaho Wolfman]

Did you buy a genuine Kubota supplied solenoid?
There are some Chinese knock off that are junk and require more amps than normal to pull it in.
You next test would be to do a voltage test on the wires when the are connected to the solenoid.
ONe wire is the pull in coil and one wire is the hold coil.
It sounds like you have a week feed on the pull in side of the solenoid.
I would need a schematic on that model, that I don't have, to know if the feed comes from the switch, a relay, the OPC, or the solenoid.

 

[RRTREU]

Thanks for your thoughts.

The solenoid is only active for a few seconds at shutoff. When the key is turned off, the solenoid pin extends a half inch. After 10 seconds, power is removed and the pin retracts.

There is a spring loaded valve built into the injection pump and the pin impacts it to cut off fuel. It pops back up when the pin retracts.

The solenoid does nothing at engine start.

It is hard to imagine how this could be a solenoid or electrical problem when everything works perfectly with no solenoid (I kill the engine by pushing in the spring loaded valve with a screwdriver.)

The spring loaded valve moves smoothly when pressed by hand and pops back up promptly (no sticking).

 

[twomany]

I have a tractor with a similar system. There is a "controller" box associated with the solenoid operation. The unit would "act up" and shut off sporadically, then not allow a restart
for some period. A defining "clunk" signalled when the controller decided to release the solenoid.

I diagnosed the problem by removing the "black box" controller. and then using the manual fuel shut off. Everything worked perfectly. On enquiry, the "black box" is priced north of $400. For a f^#*king fuel shut off!

I've threaded a length of TIG filler rod through the firewall to the manual valve. Just like the old days. It works PERFECTLY!

The black box is torn to bits down on the work bench. If I get a wild hair, I may repopulate the circuit board. I'm sure it is an aged capacitor causing the troubles.

 

[RRTREU]

Thanks twomany

It sounded promising but I can hear the solenoid pin retract about 10 seconds after shutting off the key. The defining "clunk" comes right when it should,

I may end up with a work around like yours if I never find the cause.

 

[Grouse Feathers]

I would try jumpering the interlock switches; seat, pto, and hydrostatic neutral. Easy to check and its always best to check the simple stuff before making modifications or replacing expensive parts.

 

[North Idaho Wolfman]

You think I would learn....
I jumped without looking it up, when I point out how the solenoid operated on your model.

So, back on track, times that you hear of this happening it's a start spring on the governor that is missing or stretched that causes it to delay starting.