12v Coil on Kubota

[fredbear241]

Hi Kubmech,
Thanks for confirmining there are no points. When it is working there is a spark as you suggest. When it stops there is no spark. The test you mention is what I'm doing. When it cuts out, I pull the plug & test crank, => no spark. Wait a while (from 5mins to 12hrs) and test again => sparks back so replace plug & away we go. Unfortunately & can't put my weekends on hold, to coincide with the sparks leave of absence What I'm trying to confirm is if the coil is breaking down somehow when it gets warm/hot. or if the problem is in the relay box, or maybe somewhere else. From what you say, disconnecting the small wire from the coil, really just disables the safety switch system, right? Can you tell me why it only carries ~1v? is this normal, or an indication of a problem somewhere else?

 

[fredbear241]

Hi Rich,
Only 2 wires to ign coil. 1 x HT lead and 1 x thin black wire. There are 2 green wires that go under flywheel, but these go to the charging coil which is under there.

 

[kubmech]

Yes, disconnecting the small lead disables the saftey system.
If it shuts down and you get no spark, pull the black lead, if spark comes back it's in the shutdown system and not the coil. As far as the voltage you're reading I don't know, I've never had a reason to test for voltage there. Could be just a "stray reading" The new multimeters are very sensitive. Is this tractor a T1400? Can't remember for sure but I think your saftey system uses a module and not a relay box. The easiest way to test the module is to have one you know is good and replace at the time of failure. (a luxury I realize you don't have) I have found that running the ohm/continuity tests in the manual are usually unreliable for the module, however on the relay box system, continuity tests are usually reliable. I'm pretty sure that the G1900 was the only system with the relay box. So I geuss the moral of the story is if it's not in failure mode, it's very difficult to pinpoint the exact cause of the problem. Test saftey switches for good continuity, look for any obvious wiring problems, check for good clean connections in harness for now. When/if it fails again, isolate the problem to the coil or the saftey system and we'll try to go from there.

 

[Mike_Dumond]

Hate to be the bearer of bad news, but here goes. There is no way you are going to find your problem with static tests. The test equipment needs to be hooked up when the problem occurs. Heat related problems are the hardest to find and fix. I mean, who would pay a mechanic to watch a motor run for 12 hours, just to see if it'll stop. I'm assuming you checked all visible connections first? ie: good crimps on wires in connectors, and not on the insulation. Seen it happen on lots of electrical/ electronic connections. Runs well, then shifts with the heat and presto, instant dead motor.

If this has been checked, then I would replace the CDI box or the ing. control box, (little black box). These are most likely to go bad with a heat related problem. Easiest way to fix it. But, not necessarily cheap. Especially if the problem lies elsewhere, like the coil.

Speaking of which, not sure where you live, but if you can find a small engine mechanic or snowmobile mechanic who happens to have a Merck hanging around that he'd be willing to lend you for a day or so, then you could check the coil. The Merck acts as an ignition system for a coil, allowing it to run under load for extended periods of time. Wont run the motor, just the coil.

Except for the fact that i have access to a Merck, what I would do, is check the connections, then switch out the black box.

Keep the greasy side down.
Mike

 

[fredbear241]

Hi KubMech,
Yep a T1400h. I have a small regulator which is connected to the green wires that go to the charge coil. And I have a relay box which has 2 relays on a circuit board. Relay * reg pass std tests. Both also passed testing by Auto electrician. However the motor also runs 'perfectly' - when it wants to!.
I've bypassed all the saftey switches and makes no diff. Last night I had it started, did a lap of lawn. Ignition cut while I was going along. No spark. I waited 20mins. & restarted. Did another 3-4 laps....and it cut out again. Couldn't get spark back again. This is typical. After playing in shed I get it started. Think I've solved problem. Shut it down. Reinstall all the covers etc. Restart it OK. All seems good. I might get 2mins or 30 mins running then it cuts again....no spark. Wait a while (variable length of time) & it might come back again. Usually 12hrs is the max I have to wait!. Could you rewrite the first couple of line in your prev reply....I'm not sure I follow. TIA

 

[PaulT]

I'm no expert on ignition systems - just a shade tree mechanic with an old muscle car and some lawnmowers (my new 2710 ignition is still a mystery to me - it works, so I don't have to know about how or why at this point). However, I do have some real-life experience with "black-boxes" of many types. These boxes invariably contain circuit boards. In vehicle applications, they usually are epoxy sealed from the elements. All of these boxes are subject to constant heating and cooling cycles, and are usually subject to vibration as well. These conditions usually cause a crack in the circuit board that breaks a trace, or etched circuit. Because the board expands and contracts and vibrates, the trace "edges" on either side of the crack may or may not be aligned at any point in time. A brief cooling period may cause them to realign enough, or it may require a longer cooling period. Sometimes a hit with a hammer (if its one of those epoxy sealed jobs) can jar it enough to make it work again. (I had to do this once when our family station wagon was stranded 20 miles form home, 10 miles from a service station, and 20 miles into an 800 mile vacation drive. We got to the dealer and replaced the box. 2 hours later we were on our way with no more trouble). The intermittent nature of the problem is just not characteristic of other mechanical (or large scale electrical) devices. As you say, it sounds organic in nature (something I think our semiconductor-based circuit boards are becoming/w3tcompact/icons/wink.gif). Just bite the bullet and get a new black box. I bet you won't have any more trouble until the next black box you own gets its "intermittent failure orders" from the union boss of the association of black boxes, and it is his turn to fail unreliably for you/w3tcompact/icons/tongue.gif.

PaulT

 

[kubmech]

Hey Fredbear, sorry about the wait, I was "out of town" for a few days. Number one: Forget about the regulator, it has nothing to do with your ignition system. Number two: Disconnect the small black lead going to the ignition coil and put it in the kitchen. Go mow, if you have no problem it's in the saftey system. If you still have a problem it's in the ignition coil. Just remember with the lead disconnected from the coil you will have NO way of shutting the engine down quickly SO BE VERY CAREFUL. Putting the carb in choke and loading the hst should shut the engine down.

 

[fredbear241]

Thanks for all replies etc. I've been waiting a week for courier to arrive with a new ignition coil / ignitor (all one unit.) I sort of derived that the prob was in there somewhere, hence the idea to bypass it with a 12v coil which was referenced here also. (I'd still like to figure out how to use a 12v autocoil & the magnets on the flywheel ) Anyhow, installed & mowed all weekend (18+ hrs in all) with no prob (other than sore butt!)....must get a bigger mower some day when $$ are avail. But then I'd have to go back to doing small areas around the house by hand mower :-( .....anyhow thanks again to all posters.

 

[scruffy]

Kubmech, question for your memory. Does the Kubota run an external ballest resistor? Not to unusual on Japanese products, and can be a pain in the rump. Used to have a Nissan p/u that ate them alive, until I switched to a GM coil with an internal ballest resistor.

 

[kubmech]

Scruffy, Most Kubota gas engines are magneto/electronic ignition. The only two model Kubotas I can think of that have a 12 volt ignition system would be the G1800 or is it G1900 I forget, but that's the one with the diesel "transformed " into a gas engine. The other model would be the T 1760 with the Kawasa...... oh-uh-err kubota liquid cooled 2 cylinder. Which requires 12volts for ignition. The T1400 has the Hond....uh, I mean kubota air cooled single cylinder which is a solid state magneto ignition. None of which has a ballest resistor. Although I always carried a spare in the glove compartment of my '71 Duster./w3tcompact/icons/wink.gif