I have a glitch in my Dixon ZTR 542 circuit that keeps it from starting. OTOH, I can just disconnect the ignition switch and start the engine and it runs fine. I can't seem to find any circuit diagrams or electrical troubleshooting info, All I have from Dixon is a wiring loom drawing that gives no info on how it works./
It would seem that the trouble is in the kill circuit, something is telling the engine to stop. Presumable a malfunctioning safety interlock but I'm having trouble tracing the circuit. It seems I have
12 volts to the magneto when the 'ignition' is off and 3 volts when it is 'on', but is that normal?
Any clues where to get info? I have never been able to find a repair manual for this model on ebay or elsewhere.
None of the experienced electrical/automotive folks posted so I'll just jump in.
Are there just two wires to your ignition switch? If so they may be used to provide a ground to retard the power flow enough to stop the engine. Have you checked your switch with a meter yet? If disconnecting the switch helps perhaps you just have a bad switch which is internally stuck in the "off" position? Good luck.
I wired in a kill switch, to the wire provided by the wiring harness, on a 14 hp Tecumseh motor. It didn't work correctly. The switch conducted in the off position. It turns out that the kill switch wire grounds one of the magneto coils and the voltage is high enough to arc across the contacts in the first switch I used. I diagnosed this problem partly by holding the wire and cranking the engine. Got a good jolt. Not as much as a spark plug, but still plenty strong. ERS
Generally, these "transistor" ignitions are magneto-powered, and don't need any power from the battery to run the engine. Is there some possibility that a wire was removed and put on the wrong contact? Most of them need the magneto wire grounded to run, and open-circuit to shut down. Is that how it works when you disconnect the engine from the switch? Then, just probe around on the switch until you find an isolated circuit that is closed for start and run, and open for stop. You will need a ground wire for the other contact of that circuit.
If you have replaced the ignition switch with one from an engine with battery ignition, then it will connect the magneto to the battery for start and run. If the engine ignition is not designed for that, it will not run, and may damage the ignition module. Most of the (small) tractors have an ignition switch circuit that is isolated from the battery circuit, so it can do the grounding as I mention above.
There are lots of wires on the switch, and the switch moves from off to on to start and has 5 connectors (each has several wires). I don't have a truth table for the switch so I can't tell if it's doing the right thing or the wrong thing. If I had a wiring diagram I could follow the logic and figure it out.
On "off" 2 and 5 are connected In 'on' 4 and 2 are connected In 'start' 4 and 3 are connected In the middle between on and start 2 and 4 are connected (?)
4 appears to be battery voltage
I seem to have weak or no spark, I'll have to rig a tester for the voltage when no spark. Could it be a bad magneto? It always seemed to start & run OK before it got soaked in a 5" rain, but it also ran fine once afterward, I ran it for an hour. I bought it used over 10 years ago.
One symptom of a bad magneto is an engine that will start, run a couple of minutes, and then sputter, gasp and quit. Let it reat just a few seconds, and you can start it again, but it will quit after a few seconds. So, it could be a bad magneto, a bad switch, error in reconnecting wires, etc. If it uses points (you usually have to pull the flywheel to get to the works) they may need replacing/adjusting. A bad "condenser" will also cause weak or even no spark. On some of them, the condenser is outside, on others it is under the flywheel, too. If it is electronic ignition, then the ignition module could be bad.
Does it have ONLY a magneto, or a magneto and separate ignition coil? I have a 12 Hp Wisconsin with early transistor ignition. It has a magneto connected to a coil that looks EXACTLY like an automotive ignition coil. Confused the heck out of me at first, but this system does NOT connect to the battery at all.
It has ONLY a magneto, and apparently the output is weak. It will not fire plugs with spec (.035") gap. It also fires both plugs in series, so both fire or neither fires. Before I realized this I tried cutting the spark gap to .015" and got no spark, but then I tried reducing BOTH gaps to .020" and they fired and ran the mower.
This brings up the next problem, how to get a stronger spark. Is the magneto coil weak or is the flywheel magnet weak? I might be able to jury rig a zapper to re-magnetize the flywheel magnet, or does anyone do it commercially? I could replace the magneto coil, but that will do no good if the problem is in the magnet. Is there any test to see if the magnet is up to snuff, like a pull test on a piece of iron?
I'll bet it's not the magnets. Has this mower been outside and gotten wet? Are the points clean and gapped properly? Have you changed the condenser? If yes to all the above it may be moisture in the magneto coils. They can be dried out in a 200 degree oven.Put the mag in the oven and bake for a rew hours and let it cool in the oven. The first time I tried this I was dubious. So I grabbed the plug wire and gave the mag a spin. It made my arm really hurt. ERS
No points. The mower did get a bit wet but had the problem before it got wet (that's WHY it got wet) and seems very dry now. I ran it for over an hour so I'm sure everything got up to 200 deg.
Why would it not be the magnets? Shaking a magnet for 15 years should weaken it, no? Any way to test?
Nick, Make a quick test of the magnet by holding a screwdriver tip near it - if it pulls it over to the magnet fairly sharply - the magnet is good enough - CLEAN the inside of the flywheel with sandpaper to eliminate a coating of rust (magnet face too), then CLEAN the ends of the poles of the mag - same way - then make sure mounting bolts/surfaces of the mag to the block are clean and tight (good grounding) and adjust the gap to about .010" and you should get a decent spark. HTH Ken.
Greetings nick, The reason I doubt bad magnets is because I used to mess around and restore old gasoline engines. And I have only seen one bad magnet, and it was on a very old outboard motor. I don't know how to test them other than they should hold on to a screw driver pretty well. ERS
I would of chimed in earlier but wifes in the hospital making my time short (I'm barely keeping up with reading the group). My experience with these is that Kohler magnetos are prone to failure. My bets are on a new magneto fixing your problem.
1) an internal open in one of the conductors, either primary or secondary.
2) insulation breakdown from the secondary windings to the primary or to ground. Because one end of the primary lead is often tied right to ground those two will appear to show the same symptoms.
Both catagories of faults can be intermittent, and be temperature dependent.
First off measure the primary resistance, it should be somewhere around an ohm or so. Could be as low a half ohm, as high as a couple.
Then measure end-to-end on the secondary windings. Because your mag has both ends brought out, this is easy. Don't move the coil while measuring, the earth's field will induce enough voltage in the winding if you do this to make a DVM waffle around.
This should be around 10K ohms or so. Open is bad. Less than one K is bad.
The second catagory of failure is leakage, and you really need a megger or a hi resistance ohmmeter to check this totally, but one *strong* suggestion that the insulation is leaky, is that the spark goes away when the mag coil gets hot. The trap states in the insulation will become much more strongly populated at elevated temperatures, so the leakage current will shunt the secondary winding and plugs won't spark.
If the engine fires right off when cold, use a heat gun to warm up the coil. If the spark becomes very weak or goes away when the coil's hot, that's nearly a wrap, you need a new coil. A megger test will show that a coil provides good spark with about 10e9 ohm isolation, below about
10e7 ohms it won't reliably start a motor unless the mag is really spun fast.
Don't try to spark mags with plug wires removed. They can develop enough voltage without a breakdown gap someplace to punch through their insulation. Don't take magneto rotors out of the mag body without putting a keeper on them, especially older alnico rotors. The correct way to shut down one side of a two plug, waste spark system is to
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