Mower no start

[shadetree#1]

Final test: cables directly from car battery at 12.40V, Neg cable to engine grounded, Pos cable to starter post (still measuring 12.40V), I get a spark, but starter DOES NOT WANT TO TURN!. Sheeeeeesh!

TAKE THE SPARK PLUG OUT AND SEE IF THE STARTER WILL CRANK THE ENGINE OVER.

You need to keep a heads up and not burn/toast/smoke your starter by holding voltage on it too long.
Them replacement starters are expensive for that Tecumseh.
Here is a link to look at parts lists using your model number.

https://www.jackssmallengines.com/jacks-parts-lookup/part/206820b

https://www.jackssmallengines.com/jacks-parts-lookup/part/206820b

 

[noquacks]

Final test: cables directly from car battery at 12.40V, Neg cable to engine grounded, Pos cable to starter post (still measuring 12.40V), I get a spark, but starter DOES NOT WANT TO TURN!. Sheeeeeesh!

TAKE THE SPARK PLUG OUT AND SEE IF THE STARTER WILL CRANK THE ENGINE OVER.

You need to keep a heads up and not burn/toast/smoke your starter by holding voltage on it too long.
Them replacement starters are expensive for that Tecumseh.
Here is a link to look at parts lists using your model number.

https://www.jackssmallengines.com/jacks-parts-lookup/part/206820b

https://www.jackssmallengines.com/jacks-parts-lookup/part/206820b

Wow, I didnt think about that. Great idea! Like that, there will be much lower load on the starter. Will try that tomorrow!! Thanks to all here so far that have had so much patience with me. You guys are just plain great.

 

[noquacks]

Final test: cables directly from car battery at 12.40V, Neg cable to engine grounded, Pos cable to starter post (still measuring 12.40V), I get a spark, but starter DOES NOT WANT TO TURN!. Sheeeeeesh!

TAKE THE SPARK PLUG OUT AND SEE IF THE STARTER WILL CRANK THE ENGINE OVER.

You need to keep a heads up and not burn/toast/smoke your starter by holding voltage on it too long.
Them replacement starters are expensive for that Tecumseh.
Here is a link to look at parts lists using your model number.

https://www.jackssmallengines.com/jacks-parts-lookup/part/206820b

https://www.jackssmallengines.com/jacks-parts-lookup/part/206820b

I removed the plug, and engine turned over easily a bunch if times (where with plug in, engine turned only about 1/2 circle, and stopped). So, key switch is good, solenoid is good, and I guess starter is also good. Put the spark plug back in, and now nothing happens at all. Not even a jolt from the starter.

 

[smalltimerpm]

Sounds like it is too much for starter to turn when motor lands on compression stroke. Adjusting the valves might help the situation but still might end up needing to replace the starter. Adjusting the valves is cheaper plus a normal maintenance. Hopefully it will help but I think the starter is gonna need to be replaced

 

[noquacks]

UPDATE: So desperate now, I resorted to testing all safety switches, including the key switch. Used an ohmmeter. I tested the blade safety, the clutch safety, and the key switch. All 3 were good. Only one I could not find/test is the neutral safety switch. Where is it? There is a goofy thing about my MTD mower with the lever to change forward/reverse/neutral, when placed in neutral (center position) the mower many times does not freely roll- it rolls with much resistance and sometimes, just by pushing it with resistance it eventually "frees up", and rolls easily. Not sure if this could be the problem. Anyway, I am studying the parts diagram on my brochure looking for the neutral safety switch.

Also, I tested for V on the fine orange/white wire which clips onto the spade connector on the (new) solenoid, and I am supposed to get 12+ V with key on the start position. NO voltage! No wonder why the far end red wire on the solenoid does not show 12V. And no wonder why the starter wont turn (currently, although it turned sometimes, when tested).

Anyone know where the neutral safety switch is?

 

[shadetree#1]

What is the Model number and serial number of your 1998 MTD tractor?
We need this info so as to try to give you logical answers to your questions.

The neutral safety switch is usually close to the clutch/brake rod linkage and is sometimes not easily seen in behind the engine and the plunger covered by dirt and grass. You might even have to remove the deck so as to see the body of the switch from underneath but the plastic wiring plug is usually on top of the frame behind the engine.
Sometimes the parts list WILL NOT SHOW the actual location of the switch on the frame of the tractor. You have to just knuckle down and look at the linkage and wire loom to find it's location.

 

[noquacks]

What is the Model number and serial number of your 1998 MTD tractor?
We need this info so as to try to give you logical answers to your questions.

The neutral safety switch is usually close to the clutch/brake rod linkage and is sometimes not easily seen in behind the engine and the plunger covered by dirt and grass. You might even have to remove the deck so as to see the body of the switch from underneath but the plastic wiring plug is usually on top of the frame behind the engine.
Sometimes the parts list WILL NOT SHOW the actual location of the switch on the frame of the tractor. You have to just knuckle down and look at the linkage and wire loom to find it's location.

MTD Model is 134A 667 F118, (mentioned post #27). Hope that helps. My diagram from the Tecumseh manual is sooo small, hard to tell what wires go where. EveN WITH A MAGNIFYING GLASS. Anyway, let me peek around for this switch, as you described. I am not quitting.

PS: am am also trying to ohm out some wires for continuity.......

 

[noquacks]

I found it- it is activated when the clutch is depressed all the way, and levers push down the pin/plunger on top to close the circuit, for starting (right?). I was unaware that this is called the neutral safety switch (Duhhhh). I tested this switch yesterday, not knowing it was a netrau switch. It is fine.

Thing is, none of the wires have the same orange/white wire which activates the coil in the solenoid. How does this switch interface with that Or/Wh wire which, for now, I m not getting any voltage with key ON? The end of that OR/WH wire goes to the blade safety switch. That has continuity.

 

[bertsmobile1]

The wiring on all mowers is basically the same
The power to energise the starting solenoid goes from the battery through the key switch ( B + S ) through the PTO switch then through the parking brake switch to the solenoid.
If it is a 2 trigger wire solenoid then the other terminal at the bottom is ground and on some mowers it is switched as well
My method of diagnosis is to bypass each switch one at a time with short jumpers inserted into the switch plugs
If still no then I use longer ones to bypass the loom, one section at a time till the broken wire is found.

Most CRANKING safety switches are N-O and close to make the circuit.
If the plug has 4 pins then the pair that are open with the pin out & closed with the pin in are the cranking circuit
The other pair are the ignition cut out circuit
The connections are always FLAT SIDE to FLAT SIDE and you need to be careful because it you put battery voltage down the ignition circuit for the briefest moment you will kill the magneto .
Depending upon exactly where the switches are located some go key>brake>PTO>magneto while others go key>PTO>brake>magneto .
Wire colours fade over time so an orange wire can become a tan wire when exposed to heat or light .
In fact most wires will end up tan to beige to white over time
On top of this the looms are not designed to run for more than 10 years so there is no support for the wire / crimp joint and it is very common to find a wire broken off at the crimp .
The usual symptom of this is a random fault
But a random fault can also be corrosion

I like to pull the key plug, jump the battery & start terminals then I can use a test lamp to follow the power from there .
Way easier than trying to use a meter while turning the key with our 3rd paw .

 

[noquacks]

OK, so heres what In got, based on following advice above- The blade safety switch plunger was not being depressed enough to activate the switch terminals and allow the voltage to flow to the solenoid. I tested the blade connector wire tip (tiny wire that energizes the solenoid) and was getting 12V with the safety switch removed, depressed only by hand. Then I installed it in its slot and I pulled the big blades height lever all the way to STOP which depresses the plunger on the safety switch, but got no V at the solenoid-zero. The plunger was not being depressed far enough. So I added a "shim" to the top of the plunger to take up slack, and now I do get 12v on the energizing wire! Yipeee!

Thing is, while I am getting much closer now, while I do get 12V at that wire (removed from the solenoid spade attachment) when I slide it back on the bracket on the mower frame and test for Volts I get only 6-7 V. How can that be? The solenoid is clicking, but I dont understand how it can get only 6-7 V with wire attached but yet get 12V with wire unattached. Maybe the other safety switch (the one depressed when the clutch pedal is pushed all the way down, in back of the engine area) als needs a shim, maybe supplying the other 6V?? Why am I getting just 6-7V? Thats where I am stuck now, people.

Thanks.