pony ran great, now no spark and no start

did you disconnect the switch wire at the magneto terminal? Wire could be shorted to something if you just disconnected the end at the switch.

It's possible you turned something inside the mag unscrewing the outside nut on the mag "kill wire" terminal. Open up the cap on the mag and carefully remove it. ***Note how the rotor button is timed up if it is one of those that has a gear drive on the back of it BEFORE you pull it off the shaft it rotates on.

you can check the terminal on the wire attached to the inside of the stud that goes through the mag casing to the external kill wire stud. Insulators could also be broken down around the stud and shorting it out to the case.
If this doesn't yield anything positive, check that the points are still making good contact and breaking with a gap of about 0.020". I have had the rub block break off a set in a distributer a few times.

While you are at it, you need to check that the mag shaft is rotating smoothly and it is still in time. Sometimes on shutdown or startup especially teeth will break on a drive gear and get it out of time. If you need the instructions for the timing, they're on here somewhere. Come back and we'll find them for you. They're also in the operator's instruction book.

When you replace the cap on the mag, carefully align it and press it on squarely so the spring loaded carbon brushes are pushed back into the cap sockets smoothly and don't break off.

On old tractors with worn transfer pumps, it is sometimes a lot easier to bleed the diesel injection system if you pressurize the fuel tank to a few psi while you crack all the bleeds in turn, working toward the injectors and ending up with the line nut on the side of the injector if you haven't gotten it to start by that time. A piece of innertube clamped over the filler neck with the valve stem on it will allow you to blow it up like a balloon (just a little) and maintain pressure on it while you are bleeding it out.

good luck

Here's a link to Peter and Rita Forbes' engine pages entry for the Eisman RC-2H mag originally used on the J series D2 pony motor
http://www.oldengine.org/members/diesel/Magnetos/MagData18.htm

I had a simular problem with the pony on my D8. It always started very easy and ran good. Then one day I had a problem starting. I too thought my switch was bad and disconnected it. I removed the cap and found the rotor had some cracks and replaced it, but I think the main broblem was the points needed filing again. I hit it with a file and then one of those emery boards for sanding your finger nails. blew out the dust and ran a clean paper through it and then tried to start. The pony ran good then. I don't know if oxidation built up again or maybe its better on the points to shut the pony off by cutting the gas off and letting it run dry instead of using the switch to ground the magneto.

If it is your mag i rebuild them and also have exchange units for your machine call me at 309 923 7346 or email at
[email protected] Thanks Rick Fuller

If it is your mag i rebuild them and also have exchange units for your machine call me at 309 923 7346 or email at
[email protected] Thanks Rick Fuller

Thanks for the replies. Some family came into town yesterday and we were occupied all day. If it helps we have a bosch mag. The weird thing about it is the pony previously started on one pull. We kill it by closing the petcock on the fuel bowl and letting it run dry and die before we close the mag kill switch. The pony ran for about 10 minutes spinning the main engine trying to bleed the fuel lines before we shut it down and it ran and shut down like normal. It was only off for 15 minutes before we tried to start it again for at least a hour. We tested the switch and it appeared to have gone bad showing it was grounded in both positions, so we disconnected the wire from the thumbscrew on the top of the mag and still no spark. When we came back from dinner friday night I tried a couple of times to start the pony hoping maybe it was heat soaked and just needed to cool down but no such luck. Do you have to pull the dash to remove the mag cap or is the enough room? It looks awful tight. Can you pull the mag out by just removing the dash and the 2 mounting bolts and pulling it out just like a distributor or does it have something else holding it in?

I wouldn't pull the mag yet. Maybe do some checking under the cap and try to see if the timing is correct still before you remove it. It seems to me
a failure of something is more likely than corrosion or miss adjustment problems. Anyway it's easier to check what it's doing on the engine than off unless you rig up a test stand to spin it.

Before you get carried away with dismantle check continuity across the points.
You will have to lift the wire at the upper left hand screw to do this as the whole system is grounded. May take some serious point filing to knock the oxidation off it you can't get conductivity. If that doesn't do it (most times it will) then it's on to bigger things. You can get the cover off in place but it's a bit of an exercise to do it.