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Hey all, I’m new here and am having a lot of trouble with a mower (17.5hp 42 in deck yard machine MTD) I just picked up. Long story short, it worked when I bought it (when he jumped the battery), we put it in my truck with a forklift, I unloaded it at home, replaced the battery with the standard mower battery found by the mowers in Home Depot, it didn’t start, tried jumping the battery, didn’t start. When I turn the key the engine turns maybe once per second, consistently, failing. Mower in neutral, blades disengaged, seat safety wires disconnected and he showed me the mower starts like that in front of my own eyes. I haven’t messed with the older gas or oil to drain and replace or anything.

This has been my first run in with trying to diagnose an engine, and it’s been a pretty ignorant and in the dark process haha. Things I have done: I saw the wiring from the battery to the engine etc. was pretty old and jacked up, so thinking that was the problem I ran current straight to the starter (I believe) with a battery jumper and turned it on- same thing happened as when I turn the key. Next I talk to my neighbor, get a spark plug tester from him. It lights up in sync with every failed turn of the engine, so the spark plug is good, correct? I poured a tiny bit of gas down the air intake because I read if it starts temporarily it means “yada yada” is the problem, it didn’t start which is why I’ve forgotten what that’d indicate (spark plug?).

I have a multimeter and most basic tools, I’d really like to fix this problem myself I just need a good talk down and pointing in the right directions. I can upload pictures as well if that would be helpful!

I should mention, it’s completely missing an air filter, I obiviously intend on replacing before I go out running the mower, but i didn’t think it’d be preventing it from starting, right?

Sorry for any ignorance and million thanks to anyone who might have a moment to share some advice. Appreciate it

Fin

I would start with draining and replacing the gas. If it's been running without an air filter that's not good at all. May as well pour sand into the engine.

You said you replaced the BATTERY, ... did you install the NEGATIVE terminal to a cable (usually BLACK) that goes to the frame of the machine ??
The POSITIVE (usually RED) cable should go to one of the LARGER terminals on the starter solenoid.

Now lets get your machines model numbers, should be a sticker under the seat or on back of tractor, your engines info should be on the engine itself.
see example: ..... post the information so we can find the manuals to help you.

Boobala said:

You said you replaced the BATTERY, ... did you install the NEGATIVE terminal to a cable (usually BLACK) that goes to the frame of the machine ??
The POSITIVE (usually RED) cable should go to one of the LARGER terminals on the starter solenoid.

Now lets get your machines model numbers, should be a sticker under the seat or on back of tractor, your engines info should be on the engine itself.
see example: View attachment 36414..... post the information so we can find the manuals to help you.

Click to expand...

Yes, thick red wire to the positive terminal and thick black wire to the negative. I’ve swapped batteries before, but I do think cleaning the terminals might help (but doesn’t seem like the whole problem). Here is that info:

Darryl G said:

I would start with draining and replacing the gas. If it's been running without an air filter that's not good at all. May as well pour sand into the engine.

Click to expand...

Yeah... I wasn’t even aware of what one was until I went looking. Not ideal but not much I can do about the past abuse other than not buy something like this again in the future. I’ll try changing the gas because that needs to happen regardless

GREAT for the mowers model number... (you need to save that pic and keep it safe, you will need it EVERYTIME you order parts for the MOWER !! )

Now ...... Annnnd the mystery engine numbers arrrrre ???? .........

OK I just checked your mower manual, and it looks like you have the Briggs & Stratton, eng. ( 17.5 HP )
I"m going to start a new post (in this thread to make life easier..

Make sure the battery is fully charged (12+ volts)
Be sure the engine oil is full...( not OVER-filled )
Remove the spark-plug... now using jumper cables... connect the Neg. battery cable to good frame ground and take the cable from the Pos. battery terminal and touch the cable post on the starter, the engine should spin fairly fast, ( no sense in trying to trying to start if the engine has other issues.

If that much is good, replace the spark-plug, BE SURE ALL the battery cables ends ARE CLEAN AND tight! especially the NEG. (ground) cable ..... check the solenoid wires, and make sure the solenoid (if mounted to the frame ) is touching BARE metal ( remove and clean if necessary, now try to start the mower as a "normal procedure with the key, " does it spin normally, or does it rotate a bit and then seem to "hang at a certain point" .....if it "hangs" then try adjusting the valves (see enclosed link for your Manual, see Section 1,..Page 21 ).. after adjusting valves, see if engine rotates easier now ( normal start with key procedure ) sitting in operators seat,.. blades disengaged .. push clutch pedal (if equipped)

after we get this far (if engine rotates normally) push throttle wide open ( but NOT on choke if single lever !! ) put a SMALL amount of gas in the carb throat and try to start .... POST your results !

https://docs.google.com/file/d/0B6NaqjIxWV1ybEN0LWo3azl6OUU/edit

Still need the ENGINE numbers !! see top of valve cover or engine shroud on engine

Lifting a mower with a Forklift can break things. Look for your safety switches that could be damaged or dislodged from lifting with a Forklift.

BlazNT said:

Lifting a mower with a Forklift can break things. Look for your safety switches that could be damaged or dislodged from lifting with a Forklift.

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Good thinking on that point Chuck !

BlazNT said:

Lifting a mower with a Forklift can break things. Look for your safety switches that could be damaged or dislodged from lifting with a Forklift.

Click to expand...

My first thought too BUT as I understand it the engine is spinning good and has spark. Never the less first thing I would do is disconnect the Kill Wire from the terminal on the throttle box OR Kill Wire may come out the cooling shroud on the opposite side and simply unplug. Then try starting. Be aware that you will have to have an alternate way to shut the engine Off IF it does start. Ground Kill Wire terminal with jumper, shut off gas, pull plug wire for instance.

Walt Conner

Tinkerer200 said:

My first thought too BUT as I understand it the engine is spinning good and has spark. Never the less first thing I would do is disconnect the Kill Wire from the terminal on the throttle box OR Kill Wire may come out the cooling shroud on the opposite side and simply unplug. Then try starting. Be aware that you will have to have an alternate way to shut the engine Off IF it does start. Ground Kill Wire terminal with jumper, shut off gas, pull plug wire for instance.

Walt Conner

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No I don't think the engine is spinning good... He mentioned that the engine turned over once per second and he did have a spark.....

I was gonna reply to take the spark plug out and then see if the engine turned over like it should, but Boo beat me to it..

I also think he needs a valve adjustment.... If it's a OHV engine, which I think it is......

Thaaaaanks once again for that reply Tink from a couple weeks ago ~!~!

Boudreaux In Eunice La. said:

No I don't think the engine is spinning good... He mentioned that the engine turned over once per second and he did have a spark.....

I was gonna reply to take the spark plug out and then see if the engine turned over like it should, but Boo beat me to it..

I also think he needs a valve adjustment.... If it's a OHV engine, which I think it is......

Thaaaaanks once again for that reply Tink from a couple weeks ago ~!~!

Click to expand...

Well Bo, more heads will prevail ! from what I found, he's got the OHV, like mine, good lil engines EXCEPT for the BACKFIRE upon shut-down, but I found if you bring it back to idle and let it run a few min. that will usually eliminate the loud "BANG" associated with this model Briggs, I sorta like it at times, ( scares the schitt outa anything or anybody near-by !! ) .. :laughing:..:laughing:

Hey all, sorry for taking awhile to get back here. I had my neighbor who lent me the spark plug tester come take a look at it with me. We sprayed some ether into the engine and it’s started running for a bit, then I turned it off and the starter kept spinning, we had to disconnect the batterry and the wires were getting all hot, it was freaky like a ghost machine! We determined after looking and seeing a bunch of blown wires and melted casings that it must have been on its last electrical legs and all the jumbling from being lifted and driven in the truck bed sent it over it’s edge. I definitely got played when I bought it and wish I’d taken a closer look, ******.

Anyway, it looks like I’m going to have to go wire by wire and replace them. What would really help me out with that is some sort of wiring diagram? I can go get that engine number if that’s needed, but would you all know where to find something to help me get an idea of things like that?

There is some phenomenal help here on this forum, thank you all!

All mowers are basically wires the same and they are not particularly difficult to wire up. if you can read wining diagrams.
The cranking circuit goes S on ignition switch through PTO switch through brake switch to solenoid trigger wire.
A simple daisy chain
The kill circuits are all in parallel
Seat + PTO
Seat + Brake.

Briggs did a book called "Alternator repower guide" and in it are the basic wiring diagrams of all mowers.
Toro put out the "Demystification Guide " which explains how all of the circuits work and has the wiring diagrams for Toros in it.

Most switches are double with 4 terminals in them.
Inside is a plunger with some brass on it so it either makes or breaks contact between the terminals FLAT TO FLAT.

Disconnect the wire going to the magneto before you start.
The cranking circuit is a power circuit, all others are ground circuits.
If you accidently hook up power to the magneto kill wire you will destroy it so leave it disconnected till you have finished then hook a test light between the kill wire & ground.
Go through ever operation ( spark plug removed so the engine does not start ) and make doubly sure the lamp never so much as blinks .
Then hook the test lamp to power and make sure it glows everywhere that the engine should stop.
When you are sure it is right, hook the coils back up.

I've taken these from the MTD shop manual for the 600 series mowers ( which I believe you have ) you will have to enlarge them, with your puters zoom feature to get a good view, hope this is helpful, keep us up-dated .......

View attachment 36484...View attachment 36485..

.View attachment 36486..... same as first one but changed rotation to save your n

RE-posting these because they are NOT showing up in my previous thread (THE SITE is the problem) something changes a viewable pic into non-viewable ..?????

these are the same pics, but I rotated one in the past posting to view it easier, (that's why 3 pics) it's rotated her though. ... Boo

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