54" MZ Won't start

Todd J

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I am having an issue with my 54" MZ with 27 HP Briggs engine. It will not start or turn over using key. Here is a list of things I found with it and things I did. It will start and run if I jump the solenoid.
1. I found negative battery cable not connected to engine and frame. Bolt must have worked loose. Replaced with new bolt. Still no start.
2. Tried a new solenoid. Still no start or turn over.
3. Tried a solenoid on my neighbor's mower (Bad Boy also) still nothing.
4. Tried ignition switch off neighbor's mower. Still nothing.
5. Battery is brand new.
6. Fuse on wire at solenoid not blown.
7. When jumping across solenoid mower starts and runs fine. Checked seat switch and handle switches. All good.
8. Hour meter wire is disconnected and not sure where it went. But that shouldn't stop it from starting.

When I do turn key to start I can hear and feel starter relay make contact. Tapped on all relays in case they were stuck. Even swapped one with starter relay...still nothing.

What I am missing? Hopefully someone can help.
Thanks
Todd
 

sgkent

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time to get the volt meter out and a wiring diagram.
 

bertsmobile1

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You start by looking at the wiring diagram
The only BB ones I have seen were in the combined owner/part/service manual that came with the mower which of course you read cover to cover before you jumped into the drivers seat , didn't you ? 👿
All of the BB's I have worked on use a starting relay to trigger the solenoid
The starting relay is triggered by the safety switches on both the power and ground sides
While the use of relays is very good, it adds another level of complexity
For specific help we need you model & serial numbers so we can obtain &/or check your wiring diagram .
The only one I have is for the ZT Elite 60 because that is the only one I service.
 

Todd J

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It's a Bad Boy MZ Magnum Serial # BMG5427BS06131284
The part that confuses me it that the mower will start and run fine if I jump across the solenoid. If the handles or park brake are not in proper position it won't start jumping solenoid. To me that says safety switches are working. I thought for sure when I found the negative cable not connected problem was solved, but no. I did check for continunity on negative cable from battery to engine mount bolt and all good.

Thanks for your help
 

lugbolt

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when you jump the solenoid you effective bypass every single switch on the machine. So that is not a good test of the switches, it only tells you that there is sufficient current flow between the battery and the starter to crank the engine over. The briggs will run because of how the coils are designed, they'll run with no electricity going to them--but they won't stop spark until they're grounded.

mz's were notorious for park brake switch issues so I'd look there first.
 

bertsmobile1

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Thank you for the numbers so I can check the wiring
Down side is BB used a suppliers wiring diagram which is less than useless as it does not show what any plug attaches to and is pretty well unreadable to boot.
So will will have to treat this as a Russian made mower with instructions written in Galic translated by Kenyan .
With a meter or test lamp check the seat switch , parking brake switch & lap bar switches
And these are easy because you just check for battery voltage at the plugs on the back of the switches in start mode .
These switches should be closed when the plungers are depressed
This is handy because each switch can by bypassed one at a time with a short jumper wire with a male spade ( blade to some ) terminal on each end .
The USUAL wiring is key => pto => parking brake => lap bars => starter solenoid and that is what the Elite doe . but it has 5 relays
However your mower is shown as having 4 relays
One of these will be the starter relay and send 12 V to the starter solenoid
With a bit of luck, it will have the same colour wire as the wire at the base of your solenoid
As it uses a relay, then the switches on the lap bars could switch GROUND to the starting relay while the key switches power to the starting relay
So you will have to work out which relay does what
take the cover off and listen / feel them
One will trip as soon as the key is turned on and will stay tripped in both the on & start positions of the key
This is the ignition relay if the switched terminals are 12 V or the magneto relay is the switched terminals are ground ( grounds out the magneto )
Another one will trip when you lift your bum off the seat and the key is on, that is the seat relay
The other two should be the lap bar relays & PTO relay
How they are wired up is any bodies guess as BAd Boy wiring seems to be designed by boilermakers who are colour blind .

Has it ever run and this problem just happened or did you buy a "mower with attitude" in the hope you could re-educate it ?
Most control modules switch the grounds and if you have had a bad ground connection this may have blown the module
 

StarTech

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Since the starter relay is operating check for input and output voltages.

on the relay pin 30 is the input voltage and pin 87 is the output to the starter voltage. ( wiring diagram references these as position 1 and position 5)
 

Todd J

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Thank you for the numbers so I can check the wiring
Down side is BB used a suppliers wiring diagram which is less than useless as it does not show what any plug attaches to and is pretty well unreadable to boot.
So will will have to treat this as a Russian made mower with instructions written in Galic translated by Kenyan .
With a meter or test lamp check the seat switch , parking brake switch & lap bar switches
And these are easy because you just check for battery voltage at the plugs on the back of the switches in start mode .
These switches should be closed when the plungers are depressed
This is handy because each switch can by bypassed one at a time with a short jumper wire with a male spade ( blade to some ) terminal on each end .
The USUAL wiring is key => pto => parking brake => lap bars => starter solenoid and that is what the Elite doe . but it has 5 relays
However your mower is shown as having 4 relays
One of these will be the starter relay and send 12 V to the starter solenoid
With a bit of luck, it will have the same colour wire as the wire at the base of your solenoid
As it uses a relay, then the switches on the lap bars could switch GROUND to the starting relay while the key switches power to the starting relay
So you will have to work out which relay does what
take the cover off and listen / feel them
One will trip as soon as the key is turned on and will stay tripped in both the on & start positions of the key
This is the ignition relay if the switched terminals are 12 V or the magneto relay is the switched terminals are ground ( grounds out the magneto )
Another one will trip when you lift your bum off the seat and the key is on, that is the seat relay
The other two should be the lap bar relays & PTO relay
How they are wired up is any bodies guess as BAd Boy wiring seems to be designed by boilermakers who are colour blind .

Has it ever run and this problem just happened or did you buy a "mower with attitude" in the hope you could re-educate it ?
Most control modules switch the grounds and if you have had a bad ground connection this may have blown the module
Mine has 5 relays. The center one was clicking yesterday but not today. I am NOT getting 12V at small wire on starter solenoid when key is turned. I checked for power at handle switches and seat switch and nothing. I did check continunity on each of these switches and they show good. Even swapped relay off my neighbor's mower which will start and still nothing.
This problem just started. I have had this mower since new. Bought in July 2013 from Tractor Supply (maybe that is my problem). The only things I have done in last couple of weeks before this problem surfaced was replace muffler and drive belt idler pulley.

Thanks for your continued help. This is getting the best of me.
Since the starter relay is operating check for input and output voltages.

on the relay pin 30 is the input voltage and pin 87 is the output to the starter voltage. ( wiring diagram references these as position 1 and position 5)
No voltage on either pin when key is turned or not
 

bertsmobile1

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Check the switches for making & breaking a ground contact.
The IPL for your mower showed 4 relays under a cover arranged in a square
The one I work on has 5 arranged in a line
There is one common power connection on the Elete and all of the relays are tripped using the ground contacts from the switches
I ended up writing 2 pages of notes to suppliment the lack of electrical information provided in the manual .
Perhaps there is a dealers only wiring diagram but the supplied one is less than a joke
On the Elite, the power from the key switch trips the ignition relay that then supplys power to the other 4 relays, either to be switched or to do the switching
so follow the single wire that does not have power to it back to the relay
Then you know this is the start relay
That relay should have power to the Switched pin and to the trigger pin when the key is turned on
There are five pins on the relay3 of them are in a line with one turned the other way round and one pin either side
the pins either side are the triggers, one has to be + and the other - to trip the relay
The wrong way round pin is the switched feed and the 2 pins underneath are the switched output
So now you have to check that the wrong way round pin goes to battery voltage when the key is on
After that you have to check that the side pins go battery voltage & ground with the key in the start position so they can trip the relay

The usual way this is done on ZTR's is the 2 lap bar switches ( called brake switches on your IPL ) provide the ground connection the start relay and the PTO switch provides the power feed ( wrong way round pin ) to the Switched circuit
The ignition relay ( or key ) provides the battery voltage to the trigger + pin

The alternative is the key switch ( or ignition relay ) provides battery voltage to the switched ( wrong way round ) pin
The lap bars provide ground to the trigger & the PTO switch provides the + to the trigger .

There are other ways to wire the relays but those 2 are the most common
ON the side of the relays should be the relay wiring with pin numbers and the pin numbers are usually cast into the base as well
To avoid confusion please use the pin numbers

What we need you to do is test all the pins for both voltage & ground
And this needs to be done everything off
key in the run position lap bars in the off position PTO off
Key in the run position lap bars in the on position PTO off
Key in the start position lap bars in the off position PTO off
Key in the start position lap bars in the off position PTO on
From that we should be able to work out how it is wired
 
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