Who's Up for a Real Mystery? MTD Problem...

[deandome]

I have a mid-eighties Montgomery Ward/MTD 17hp/42" tractor (all manual tranny, etc). Model # is TMO 3100002 (here's the manual, if that helps: http://manuals.mtdproducts.com/mtd/DocGetter?doc=770-8087h.pdf )

Anyhow, I got it out for the first time this year a few days ago, it fires up fine (as it's done for the 10 years I've owned it), and I cut the front yard fine. Right at the end of that, I hear the motor bogging down/conking out, sounds like it does when it runs outta gas, so I raise the deck/disengage the mower & turn it off.

There was gas left, but I add a buncha fresh gas to top it off...start up and it runs fine, UNTIL I try to engage the mower...then it bogs/dies.

Figuring it might be a problem w/the deck (bad bearings causing lotsa friction or something), I remove the deck & the belt completely.

Here's the mystery part....it STILL bogs down & dies when you move the mower deck lever out of "off", even though the deck isn't sucking any 'power' from the motor!!! It doesn't matter if you're in park or driving, it just bogs/dies (I always disengage before it actually dies, though).

Does anyone know what this might be...what I should check? The belts are old, but they seem fine, and the main double-pulley below the engine (that drives the deck & the transmission) isn't even driving anything when it bogs/dies (no deck/in park)!!! I can't see, or even imagine, how moving the mower deck lever could effect the engine, if the mower isn't even on the tractor!

Any help would be appreciated..THANKS!

 

[waynokakid]

One of the first things I would check in that situation. Is the vent on the fuel filler cap. That will cause a small engine to act like that. May have gotten plugged while in storage by wasps, mice or such.

 

[rec]

check the seat switch

 

[brin]

Might as well check the air filter...could be when under load it sucks more air...????

 

[sailorman]

My guess. A safety switch thinks you are in reverse and will not allow engine to run. At least that's the way mine works. If I engage reverse with mower engaged engine kills.

 

[deandome]

Air cleaner was clean, even took off pre-filter. New fuel filter & fuel line put in, along w/all-fresh, premium fuel.

Still same problem.

I thought of the safety switch, but I don't think that's it. The 'bog-down' is distinctly different than the seat-switchoff; it's clearly a hard strain, like the motor's fighting against something (and losing!) vs. a smooth/fast cutoff. And like I said...I was mowing fine for 1/2 hour & it the problem just kicked in.

Now, maybe the switch is kind of 'semi-activating' even when I'm seated, so the fuel gets partially cut off or something, but the switch looks to be a simple contact-plate kinda thing, and the plates are separated/straight/fine-looking. As for the reverse switch, I'll take a look, but reverse wasn't part of the process; again, I can be in 'park', engage the PTO & it'll do the struggle & bog thing.

What's so odd, to me, is that this happened when the deck was off...when there was NOTHING dragging on the driveshaft pulleys!!

 

[zman007007]

sounds like it maybe electrically related. check pto switch for shorts. zman

 

[deandome]

Thanks, all!

I'm ALMOST ready to give up & burn most of my tax return on a new tractor. So I was talking to a few dealers & asked them about this problem, and they seemed pretty sure it had to be a safety switch problem, given the fact it happens when the deck isn't attached. They mentioned a PTO safety switch...

I knew about the one on the seat..it's fine. I know there's one for reverse, but this problem has nothing to do w/that...it happens in forward & even 'park'.

So I reexamined the diagram & saw the PTO safety switch. It's certainly hard to access, but I did clean a LOT of grass from that center 'channel' where you see the steering linkage, etc. Maybe there's some more messing w/the switch, so I'm going to give it one more try tonite after work.

I also see there's a solenoid in the main leads coming off the battery (see diagram on pg. 30: http://manuals.mtdproducts.com/mtd/D...=770-8087h.pdf ) ...is that what actually cut's off the engine? Maybe I'll look at that too (yes..disconnect the battery leads first!!)

Finally, as a last gasp, is there a way I could TEMPORARILY 'bypass' the PTO switch & wire them together to see if that fixes things? Looking at the diagram, there are two orange wires & two yellow wires connected to the switch. Would I just wire the yellows and/or the oranges together?

If I clear up this problem, I WILL get this machine thoroughly checked out & reconnect that switch. It's just that all the repair shops are quoting 2-3 week timeframes, and I can't wait that long, as my yard is already a jungle!!

THANK YOU ALL...this board is a wonderful resource for this problem & for helping me pick out a good replacement (but would REALLY prefer not to have to buy).

 

[deandome]

Sorry...the working link is in the first post of this thread! I cut/pasted it...but it looks like the site "abbreviates" email addresses so when you 'cut' it, it doesn't copy the actual address.

Here it is: http://manuals.mtdproducts.com/mtd/DocGetter?doc=770-8087h.pdf Wiring diagram is on pg. 30

Thanks!!!

Yes, you can bypass the switch, but I can't comment on which wires for sure as the link wouldn't work. I did have an old Bolens where a 2 wire safety actually ended up shorting to ground instead of providing a completed circuit between the 2 wires.

 

[Craig Clayton]

Dear deandome
I posted my experience with a dealer under BRIGGS 11 HP oil seal, they do not always give you straight advice. On your machine check the air over the cylinder head for a mouse nest etc, your points or plug should checked,fuel filter replaced.
When the machine cools down does it start and work properly until it acts up, because it is a heat issue with some component.
Craig Clayton