Help Resurrecting a 312-8

[chesbaycruiser 83]

Last weekend I picked up 1988 312-8 purchased on e-bay, with the idea that, depending on condition, I would either get it running or part it out. It seems solid enough...I've removed the mouse nests and cleaned it up some, and I'm pretty sure it will run without too much effort.

Right now, though, I'm a little stymied! I've got no spark, and I'm not sure why. I'm no expert in small engine repair, but as I read the service manual, basically the only things involved in creating the spark is the flywheel/magnet, magneto ignition module and the plug. I've checked the wires, replaced the plug, cleaned and gapped the magnet & ignition module, but I get nothin'! The guy I bought it from tells me he replaced the ignition switch and installed a new ignition module.

Is there something I'm missing? Any thoughts or suggestions would be appreciated! If a safety switch was bad somewhere, would the engine still turn over but kill the spark?

[Save Old Iron 1,571]

Does the engine turn over via the ignition switch ?

[chesbaycruiser 83]

Yes, the engine turns over strong.

[Save Old Iron 1,571]

And how are you testing for the presence of a spark ? If you are removing the plug from the head - make sure the plug is grounded well to some part of the engine - make sure the plug is not defective or flooded with gas and not able to spark.

You could also remove the kill wire from the magneto and try to start the engine - if it does - do not let the engine run without the cooling skins on - kill the engine by reattaching the kill wire to the magneto.

also check if the previous owner used the correct ignition switch designed for magneto ignitions

[dscott2000 1]

This is what I do on most occasions. Just take a peice of sandpaper and clean any and all grounding connection points. (this requires that you will have to remove the coil.) Clean the mounting points as well as the coil itself. Then, clean the magnet on the flywheel. (It doesnt have to be shiny. But, it helps.) Now, when you go to put the coil back on the engine. Use either a flimsy peice of plastic or a feeler gauge at .020. This should give you spark. If not, your coil has gone bad. I have done this to many, MAAANY mowers and it works like a dream! Also, change your spark plug. This will help. I hope this fixes at least part of your problem!

[hodge 6]

On my 310, I had disconnected the safety switch for the PTO, and it would turn over, but not fire. Check your safety switches.

[WH nut 553]

Unplug the connection to the motor and spin by hand. If you have spark then, you know its in the wiring or staety switches

[chesbaycruiser 83]

save_old_iron - I am testing the plug out of the block, but grounded firmly against it. I've tried with 2 differnt plugs, one of which is brand new. Tried it with the kill wire connected, and also removed.

dscott2000 - Removed the coil, cleaned all contacts and regapped as spec'd by the service manual.

hodge/WH_nut - all safety switches seem to check out, however tried with all connections disabled and spun flywheel by hand. Still no joy.

Current status - Although the coil is supposed to be new, I'm pretty sure it is bad. I checked the resistance at over 25K ohms. Service manual calls for 7,900-20,000. Also, based on some continuity tests, it looks like the ignition switch that was installed is not the correct one.

So I'm thinking maybe using a switch that is not a "break befor make" may have fried the coil, or possibly trying to start the tractor with the ignition switch in the "run" position by jumping the solenoid leads?

Any other thoughts or feedback are welcome!

[Save Old Iron 1,571]

. Also, based on some continuity tests, it looks like the ignition switch that was installed is not the correct one.

This is a mistake that is too easy to make.

Obtain the correct switch and restest - you have done a great job in actually troubleshooting the problem and avoiding "just slam parts in" method of repair, but I think we are looking at a dead magneto. If you remove the kill wire and still do not have any spark, look at replacing the coil.

And just so it's been said - "new" doesn't always mean "good"

Your on the right track with the coil and switch (re)replacement.

:scratchead:

[HorseFixer 2,013]

Nice looking tractor Looks like Ole Iron has you heading down the right path! :scratchead:

[chesbaycruiser 83]

Thanks for all the help and input. For a rank-amateur like myself, sometimes even though you THINK you know what the issue is, it's nice to have more experienced minds confirm (or correct ) your thinking!

I'll keep you posted, and I'm sure once the spark issue is corrected, I'll be back whining about the carb!

Thanks again,

Chris

[chesbaycruiser 83]

...you have done a great job in actually troubleshooting the problem and avoiding "just slam parts in" method of repair...

Thanks Iron, although I must admit that part of the reason for that is prety self-serving.

This tractor was purchased as part of a grand, "move up the tractor ladder" plan, so I'm spending as little as possibe, especially early on. It was essentially purchased sight unseen with the intention of either getting it running, cleaning it up a bit and then re-selling it (the preferred option), or, if it's problems appear too great, parting it out.

Right now, I'm still operating under the assumption it's option #1, but until I'm certain, I want as little cash outlay as possible! Once I'm sure of it's potential, I'll be (a little) more liberal with the $$$! :scratchead:

[chesbaycruiser 83]

In the "for what it's worth department"...bought a used mag/coil on ebay, picked up the proper ignition switch, installed a new feul line, taped a few safety switches closed (most of the tins are off) and viola!!! Running like a....well....like a Wheel Horse!!!

Thanks for all the help!

Chris

[rickv1957 74]

Chris,I had to buy a new mag for my 312 a while back,it lost spark ,Rick