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Murray stalls when blades engage

#1

ben.cellamare

ben.cellamare

Just finally got my older Murray back to working order, but when I engage the blades the engine stalls. Any ideas why? I originally bypassed the seat switch so that is not even an issue at this point. Any direction would be helpful. Thanks


#2

B

bertsmobile1

The safety circuits are all ground circuits so if you have a short anywhere it will not make any difference weather you bypassed a switch or not .
When you turn the blades on you do several things
1) Activate a safety circuit PTO + Seat Switch
2) Start spinning the blades
3) Open the throttle further .

So while you have the belt off turn the blades on
If the mower dies you have an electrical problem
If not it is mechanical or fuel related

NExt test is to set the parking brake and manually open the throttle by pushing the governor arm
If the engine faulters then you have a fuel problem

If both of those are negative then the problem is with the clutch itself


#3

ben.cellamare

ben.cellamare

bertsmobile1 said:
The safety circuits are all ground circuits so if you have a short anywhere it will not make any difference weather you bypassed a switch or not .
When you turn the blades on you do several things
1) Activate a safety circuit PTO + Seat Switch
2) Start spinning the blades
3) Open the throttle further .

So while you have the belt off turn the blades on
If the mower dies you have an electrical problem
If not it is mechanical or fuel related

NExt test is to set the parking brake and manually open the throttle by pushing the governor arm
If the engine faulters then you have a fuel problem

If both of those are negative then the problem is with the clutch itself
Click to expand...
I will try and keep you posted. Thank you


#4

ben.cellamare

ben.cellamare

bertsmobile1 said:
The safety circuits are all ground circuits so if you have a short anywhere it will not make any difference weather you bypassed a switch or not .
When you turn the blades on you do several things
1) Activate a safety circuit PTO + Seat Switch
2) Start spinning the blades
3) Open the throttle further .

So while you have the belt off turn the blades on
If the mower dies you have an electrical problem
If not it is mechanical or fuel related

NExt test is to set the parking brake and manually open the throttle by pushing the governor arm
If the engine faulters then you have a fuel problem

If both of those are negative then the problem is with the clutch itself
Click to expand...
So I took the belt off and engine still turned off. I tested the clutch sensor and the blade sensor, both of them work (have continuity). And the seat safety switch I bypassed.

I will try the governor arm next.


#5

B

bertsmobile1

It is electrical
Engaging the blades without the belt will not put enough load on the engine unless the battery is dead flat .
So either there is a dead short in the PTO circuit or a ground short in the blade safety circuit .


#6

ben.cellamare

ben.cellamare

bertsmobile1 said:
It is electrical
Engaging the blades without the belt will not put enough load on the engine unless the battery is dead flat .
So either there is a dead short in the PTO circuit or a ground short in the blade safety circuit .
Click to expand...
what is the best or easier way to find the short?


#7

B

bertsmobile1

No easy way to do it .
You have to unplug everything then plug them back in one at a time till you find the culprit
You really need a wiring diagram to make sure you do not cross a power circuit with a ground circuit .
I use short jumpers to make connections on the power side then one at a time connect the ground till the engine stops or I get a ground on the kill circuit depending if I have the kill wire test lamp with me .

We have now got to the point where you need to tell us a lot more about your mower.
Starting with the model number
Electric or manual PTO etc .


#8

ben.cellamare

ben.cellamare

This is the wiring diagram. I have a Murray 38608x92c with a manual PTO


#9

ben.cellamare

ben.cellamare

Here it is

Attachments





#10

ben.cellamare

ben.cellamare

I have a new ignition switch. 15 and 16 is the blade engage switch I have pulled it and tested it and it works so there must be something electrical as you stated.


#11

B

bertsmobile1

IT is so much easier when people post proper details of their mowers from the first post.
The magneto kill wires are the yellow ones.
To kill the magneto the yellow wire goest to ground
This can happen either by the key switch connecting the yellow to ground
or
ground going through the seat switch then through the PTO switch then to the coil .
So you have either a short in the yellow wire between the seat switch plug & PTO plug
Or the PTO switch itself is grounding the yellow wire via an internal short .


#12

ben.cellamare

ben.cellamare

Could the PTO switch ground itself via internal short and still show from the multimeter that it is in working condition? (via continuity) Also when I try to engage the blades the blades start to move but the motor just turns off.


#13

B

bertsmobile1

Anything is possible
The safety circuit to protect idiot hands from being chopped off when they try to clean out a blocked chute with their fingers while the mower is running has 2 switches in it.
The seat switch & the PTO switch .
When the seat switch is in the "no one home position " and the PTO switch get put in the "chop your fingers off position " it grounds the coil & kills the engine or trips a relay & turns off the blades.


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