Murray model 42819a engine will not turn over

[Fremont]

My 90 year old dad has a mid 1990 Murry Lawn Tractor. It does not turn over. Checked the Solenoid, OK, Battery OK, Jumped the Starter and it turns over OK. I'm thinking it might be one of the Safety Switches. Any other things that might cause this?
Also, does anyone know which wire goes on the Solenoid? Not sure that is wire coreectly. I know where the Big red ones go, but there is a Smaller Black and Red one. Just want to make sure they are in correct places. Can not figure it out in the wiring diagram.

 

[SeniorCitizen]

This is a Murry schematic of approximately that era that may help.

 

[bertsmobile1]

The red wire with the big red terminal goes to the battery side of the solenoid as it is the power source for the rest of the mower including the trigger wire for the starter solenoid.
Some where between the solenoid & the key switch will be a fuse, usually 15 or 20 A
A single small wire with a tab terminal on it goes to the base of the solenoid.
If there are two such wires they go on either terminal, it does not matter which one .
The cranking circuit goes key switch , brake switch PTO switch then solenoid .
I usually pull the key switch & plug out
On the back of the key switch usually you will see the letters GMBSA ( or more )
You jump the B ( battery ) which should show battery voltage to the S ( start ) .
If the safety switches are in the right position for starting and the engine cranks, the key switch is bad
If not one of the safety switches or the wire between them is bad
From memory they are both on the right side of the mower, one under the dash & the other under the floor
With the key switch still jumped. jump the safety switch plugs , FLAT TO FLAT because some have 2 circuits passing through them
If you have jumped them all & the engine still does not crank then one of the wires is broken so you bypass the wires one at a time till the engine cranks .