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My snapper ztr with a Briggs and Stratton 27 HP 2 cylinder engine. Model # 49T877-0025-G1.Cranks but will not start. No spark to either plug. If I disconnect both kill wires at the coils, it will start and run ok. If I reconnect 1 of the kill wires, it will cause that cylinder to miss, same with either cylinder. If I re-connect both kill wires it will lill the engine. What do I need to do to correct this problem.

The kill wire has diodes in it that like all diodes go bad with the effect of heat
With some one in the drivers seat & parking brake on check the kill wire .
With the key in the ON position it should be open circuit to ground ( check both terminals )
Get the person to release the brake, it should still be open circuit
Get them to stand up and it should go to ground
Get them to sit back down again turn the key on set the brake & move the lap bars
The wire should go to ground again
It should go to ground when the key is in the off position regardless of any other control position.
If all this checks out the diodes have gone
You can double check the wire as with the meter connected to any pair of terminals one way should be open circuit & when the probes are swapped it should show a close circuit
The diodes are about $ 5 for a 10 pack or the wire with diodes can be replaced for around $ 40
It is a Briggs & Stratton part # 591392 not a Snapper part

bertsmobile1 said:

Briggs & Stratton part # 591392

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Thank you for your reply. I will replace the diodes.

Travlitt said:

Thank you for your reply. I will replace the diodes.

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Check them before you replace them
Always best to work out why a failure is occuring before you got throwing new parts at anything and adding even more potential problems.

Search the archives for Briggs & Stratton diodes if you want to replace them & not the whole shooting match
I am dyslexic so will get the numbers wrong but he posted them a few years back and I bought a 100 pack for $ 12 Aus .
Used about 10 of them & given away about 20

bertsmobile1 said:

Check them before you replace them
Always best to work out why a failure is occuring before you got throwing new parts at anything and adding even more potential problems.

Search the archives for Briggs & Stratton diodes if you want to replace them & not the whole shooting match
I am dyslexic so will get the numbers wrong but he posted them a few years back and I bought a 100 pack for $ 12 Aus .
Used about 10 of them & given away about 20

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I changed the diodes but it still will not start. I have a ground on the kill wire at all times. With the switch on, lap bars out, pto OFF, break on ans seated I still have a ground and no start.

bertsmobile1 said:

Check them before you replace them
Always best to work out why a failure is occuring before you got throwing new parts at anything and adding even more potential problems.

Search the archives for Briggs & Stratton diodes if you want to replace them & not the whole shooting match
I am dyslexic so will get the numbers wrong but he posted them a few years back and I bought a 100 pack for $ 12 Aus .
Used about 10 of them & given away about 20

Click to expand...

Then you have a safety switch failure
The kill wire should either be ground = no spark
Or open circuit = spark
this is why you test the the modules by removing the kill wire
Sorry I misread your original post .
We need the actual model number in order to pull up the wiring diagram
Generally
1) parking brake + lap bars
2) parking brake + kill switch
3) Seat switch + PTO
Control modules & relays complicate this some what .