Engine shuts down when steering arms are engaged…

[TXBodie]

Hey guys, I need some help before my MZ Magnum suffers from an acute case of lead poisoning….
Ok, here it goes. Mower just stops moving while I’m actively mowing. A loud grinding noise is heard right before it rolled to a stop. Look under it and discover the drive belt is shredded so that solves that mystery. After disengaging the pump motors by pulling out both rods and securing with pins, I hooked a chain to the front wheels from my loader bucket on tractor and towed it onto my driveway. Replaced drive belt, set tensioner spring by eyeballing it, re-engaged pump motors, then hopped on it and cranked it up. After disengaging the parking brake, I try to engage the steering arms and the engine dies like it’s tripping some sort of safety switch or something. This is driving me nuts! The PTO engages just fine, so it’s not the seat sensor… Anyone got any bright ideas? I feel like this is something simple and obvious, just not to me. Thanks in advance!!

Bodie

 

[TXBodie]

I just realized what caused all this mess….a nut had vibrated off one of the battery support rods and the rod sets directly above the pump motor fan and pulley, so when it fell, it fell directly down onto the spinning fan shredding it and then ultimately the belt. This is an obvious design flaw that will eventually cause damage to most mowers, so you might want to take off the OEM battery support off and secure the battery some other way.

 

[bertsmobile1]

There is a shut off that connects the lap bars to the parking brake so you can not drive off with the brake on .
Could still be the seat switch or the set switch relay
BB publish their loom lay out and think it is wiring diagram and I have never been able to find a reliable wiring diagram for any of their mowers
Thankfully they have abandoned the Australian market so the single one I have to suffer with will hopefully be the only one
Very generally the safety circuits that cut out the engine are
Seat + PTO
Seat + parking brake
Parking brake + lap bars

The one I service has a 2 wire seat switch and a pile of relays and these relays do give a lot of problems

 

[TXBodie]

Well the wife got tired of hearing me curse the sky & came out and crawled her small frame underneath it and of course she discovered the wires going to the brake sensor got all stripped and twisted up together when the belt shredded apart. I clipped them back and reconnected them and she runs like a champ again!!!

 

[StarTech]

See what a different set of eyes can do sometimes. Even someone totally inexperience or that know nothing about an item can point out something. I once was working a calculator for nearly 30 minutes looking a particular component. I couldn't seem to find it then the operator walks and just asks what an item on the circuit was. And it turn out to be exactly what I was looking for. She had no knowledge what I was working on but was still curious enough to help me out.

So yes someone else can point out something that you were overlooking. This why when I get stuck on a problem I just put the unit aside and work on another unit and come back later with a fresh view point.

 

[bertsmobile1]

Sounds like a win to me
I hope you took her out to dinner

 

[BigBlueEdge]

Replaced drive belt, set tensioner spring by eyeballing it, re-engaged pump motors, then hopped on it and cranked it up.

Per my BB dealer, the drive belt tension is set correctly when a credit card (or .030 feeler gauge if you have one handy) slips between the tensioner spring coils without much effort, but not loosely.