Seat safety switch

[Save Old Iron 1,566]

what you have pictured there is a starter relay

[tthan43 1]

what you have pictured there is a starter relay

Well....shoot. Hmmmmm........I'll go out in a little bit and take a look again at the stuff under the hood. Will the magneto be housed under a cover or internally inside something?. Bet I can find it. It should stick out like a sore thumb tho unless it is under a cover of some sort.

[Save Old Iron 1,566]

Since we are on page 3 with this post, now might be a great time to recap exactly what is is we are trying to address (engine dying when PTO is engaged?)

You will need to pardon me, I have a short attention span these days.

Maybe a quick run down on what steps you have taken so far.

To answer your question posed in the post above, the magneto is located under the engine cooling tin. The photo I posted of the 416 has the tin removed and the magneto is positioned at the 12 o'clock position directly above the flywheel. A magnet located on the flywheel runs past the magneto, inducing a large magnetic pulse into the magneto. The magneto converts this magnetic energy into a spark to fire the engine.

Working this problem from the other direction .... grab the spark plug boot. Follow the plug wire back into the engine area. The wire will end at the magneto.

[tthan43 1]

Since we are on page 3 with this post, now might be a great time to recap exactly what is is we are trying to address (engine dying when PTO is engaged?)

You will need to pardon me, I have a short attention span these days.

Maybe a quick run down on what steps you have taken so far.

To answer your question posed in the post above, the magneto is located under the engine cooling tin. The photo I posted of the 416 has the tin removed and the magneto is positioned at the 12 o'clock position directly above the flywheel. A magnet located on the flywheel runs past the magneto, inducing a large magnetic pulse into the magneto. The magneto converts this magnetic energy into a spark to fire the engine.

Good idea:

1. Mower starts fine and the smoke problem seems to have diminished greatly. Will tackle that problem a little later if it persists.

2. Main problem now is the motor dying when I slowly push the PTO engage lever forward...the engine will die even when the PTO belt is removed from the pulley. Whatever I do, the engine will try to die when the blades first start to turn and if I push the lever a little farther, it will die. Mower will not continue to run if the PTO lever is fully forward.

3. The Seat Safety Switch light on the instrument panel remains lit when key is on whether I am sitting firmly on the seat of not sitting. The little red light stays lit. I have raised the seat, disconnected the seat switch from the plug, put in a jumper wire and the seat light remains on and has no effect on the engine dying when the PTO lever is engaged.

4. Haven't ferreted out the magneto check yet as I was not sure where it was or what it looked like. The owner and user manuals that I have are not very thorough and the trouble shooting is sadly lacking in details and analyses. The problem is that I don't read schematics. Never had the need to. Sure would come in handy though for stuff like this. Electrical problems can be a epic event to diagnose, esp. in much larger items like cars and trucks. This mower should be a lot simpler.

Someone mentioned a PTO switch. I have no idea where that is and the manuals only give a passing mention of it...nothing about its location or trouble shooting techniques. I have a little volt meter and I would assume I could check the voltage output in some way to test if the magneto was putting out a current. If it is, then obviously, that would eliminate any magneto problems wouldn't it? The way I understand it, the magneto does much the same job as a generator....produces electricity.

[tunahead72 2,424]

2. Main problem now is the motor dying when I slowly push the PTO engage lever forward...the engine will die even when the PTO belt is removed from the pulley. Whatever I do, the engine will try to die when the blades first start to turn and if I push the lever a little farther, it will die. Mower will not continue to run if the PTO lever is fully forward.

Just to clarify, because I'm not sure I understand ...

You've completely removed or at least loosened the mower drive belt, the one that goes from the engine to the mule drive and back to the mower deck? If so, how is it that the blades can still turn when you move the PTO lever?

One other thought -- can you rotate the mower pulleys or the blades by hand? There's not a big rock or something else jammed up under the deck, is there?

[tthan43 1]

2. Main problem now is the motor dying when I slowly push the PTO engage lever forward...the engine will die even when the PTO belt is removed from the pulley. Whatever I do, the engine will try to die when the blades first start to turn and if I push the lever a little farther, it will die. Mower will not continue to run if the PTO lever is fully forward.

Just to clarify, because I'm not sure I understand ...

You've completely removed or at least loosened the mower drive belt, the one that goes from the engine to the mule drive and back to the mower deck? If so, how is it that the blades can still turn when you move the PTO lever?

One other thought -- can you rotate the mower pulleys or the blades by hand? There's not a big rock or something else jammed up under the deck, is there?

thank you for the inquiry. Yes, I completely removed the belt from the PTO pulley after loosening the tension with the knob on the mule drive. I took the belt completely off the PTO pulley. Yep, the blades turn easily by hand. No binding there.

[can whlvr 993]

you need a spark tester to see what is happening to the spark when this happens

[tthan43 1]

you need a spark tester to see what is happening to the spark when this happens

Thanks. I can get one at our local auto parts house tomorrow. Will I check for the strength of the spark...is that the thing I will look for?

[bo dawg 516]

The PTO switch should be right under the PTO lever next to the battery. I don't think yours would be any different. When the lever is forward the linkage off it engages the switch.

[tthan43 1]

The PTO switch should be right under the PTO lever next to the battery. I don't think yours would be any different. When the lever is forward the linkage off it engages the switch.

Hey..thanks a lot..I was looking at the schematics in the manuals and I could not figure it out. And no where in the manuals does it show or explain where the thing is. It mentions it in the little list of switches but that is it. These old 1998 manuals are really lacking in detail. That is where I will look. I wonder if the problem I am having could somehow be connected to that switch. Hmmmm........... When the lever is pushed forward to turn on/engage the PTO so the mower blades will turn, the motor dies. Somehow, SOMETHING is not working right. Shoot, it was working perfectly about a week before I ran into the problem. Got lots of mowing done. Put the machine up, went out a week later and there's the problem. Just weird. Thanks again....I will tear into it and see what the deal is.

[Save Old Iron 1,566]

Here is a theory I would like to advance.

Incorrect operation of the "Seat Relay"

I will try to make the case by explaining the normal operation of the relay then explain your issue as could be caused by defective operation of the seat relay. (click on image to enlarge)

Situation A - Normal operation - PTO disengaged

PTO switch is "disengaged" which means there is no connection to the Kill wire on the magneto. You spin the engine and feed it gas and it will run.

Situation C - defective seat relay - PTO disengaged

PTO switch is still "disengaged" - once again, no connection exists to to ground the magneto kill terminal via safety switches. Even with the seat relay being defective (relay internal contact stuck on ground), the tractor will start and run with the PTO disengaged. All still appears normal at this point, but no grass is being cut at this time.

Situation B - Normal operation - Tractor Running - PTO closed

operator engages PTO lever - PTO switch now electrically connects the magneto kill wire to the safety switches. In this properly operating mode, the magneto kill switch is still not grounded due to the proper operation of the seat relay. With the operator seat switch engaged (you are sitting in the seat), 12 volts is applied to the coil of the seat relay. This causes the relay to activate and disconnects the yellow wire from the ground connection (BLK wire).

The engine continues to run since the seat relay has removed any possibility for the yellow wire to be grounded. Hey look at you, you're cutting your grass! Hurray!

Situation D - Defective operation of the seat relay - PTO switch closed

Due to a defect in the relay or associated wiring, the yellow wire remains grounded thru the relay contacts. When the PTO is engaged, the magneto kill terminal becomes grounded and kills the engine as soon as the PTO is engaged. Please note: the dark blue magneto wire is most likely not at fault - if is was, the magneto would never spark and the engine would never start. The PTO microswitch appears functional - in the disengaged position, the tractor starts. When the switch is activated in the engaged position, the engine stops running - following the action of the switch. Using this logic, I believe the fault lies in between the seat switch but before the PTO switch.

Soooo... some possible areas to investigate.

I am not familiar with the 300 series tractor and possible similarities to a 400 series. On my 416, an electrical connector just outside the engine tins support the oil level switch wiring, the B+ from the rectifier and the kill wire.

If your setup is similar to the drawing below, removing the kill wire temporarily from the harness will prove the case for the engine dying due to incorrect function of the seat relay / wiring.

That's it - just a theory.

[bo dawg 516]

nice detail Old Iron. I like that.