Defective ignition switch?

[bertsmobile1]

"Calculator disease". Got to love this guy LOL

slomo

It is a bigger problem than many would think
Those over 60 were taught why and roughed the numbers because the absolute numerical value is not important .
Those under 60 worry about the difference between 1.2Ω and 1.3Ω which in many cases is the pressure on the end of the probe
Those under 40 can not understand why the old one that was 1.27016321 Ω did not work when the specs said 1.2 Ω
Or the one that floored me ,
"The switch you sold me is defective because I get a different ohm reading between the terminals ever time I turn it. "

 

[Telesis]

I too had to laugh at 'calculator disease'! The form of it I witness these days is when someone 'fat-fingers' the buttons and is confident in whatever number is displayed, not thinking at all about how reasonable the answer is, and will defend it "because the calculator says so, it's gotta be right"! I'm 62 and mine was the last engineering class at my university to be taught how to use a slide rule (or slipstick!). 'Slide rule disease' was putting the decimal point in the wrong spot lol!

 

[StarTech]

Believe it or not calculators can add wrong sometimes. I know as I had to change out nearly 200 cpu chips in the Victor 600 series calculators back in the early '80's. And Victor had the same attitude that it was impossible for them to do it. Several 100 of us techs proved them wrong.

As ohms reading; unless, you got a milliohms meter that can be zerod out even the leads can cause reading differences. In the small engine world close is usually good enough until EFI get fully incorporated then these tiny variances will drive the CPU crazy. Just depends how tightly they are programmed.

 

[bertsmobile1]

Meters are the opposite to every other tool I use.
All of the on site service tools are good quality domestic grade so when I loose one on site, no great financial loss .
The Stahlwile , Sidchromes & Dufors stay in the workshop .
In the workshop I use test leads with either a buzzer or lamp on
In the field I use expensive looking multi ,meters but just ignore the numbers .

 

[tkos115]

So, as an update. I went through and verified all the pins were correct, (which they were). I went through each wire to make sure that nothing was shorted out, and made sure that all the safety switches were good, (they also were). I bought a new quality switch from a local suppler and installed it. Well.... still no spark when cranking over.. At this point I'm about to pull my hair out as nothing is making any sense. After fiddling around with some stuff and watching for a spark as I crank it I noticed something.. If I let off the switch when cranking it just a tiny bit the spark comes back, if I turn it all the way to the stop on the switch it goes away again. For the heck of it, I did it with the old new replacement and it does the same thing. Anyone else had this issue with new switches? So far two brand new switches are doing the same thing. I will see about swapping the newest one out for a replacement as it seems to be defective as well. But at least it seems it's a switch issue not a wiring problem.

 

[bertsmobile1]

Take the blower housing off and pull the kill wire off
Remove the spark plug and check that you get continuity too ground in the off position and open circuit to ground in all other positions including when cranking .
If this is not the case then either the kill wire is shorted to ground some where or a switch is shorting it to ground.
As for the latter the most likely suspect is the PTO or brake switch .
Like Dorothy following the yellow brick road, you need to follow the yellow wire
In both the cranking and the running positions the yellow wire should always be open circuit to ground
The yellow wire goes to ground to kill the magneto spark
The safety switches are primative sliding contact switchs and regularly go bad

The easiest way to test them is to bypass them by unpluging then bridging the other pair of wires ( orange ones ) which are the cranking circuit
If the mower fires up as it should then plug them back in one at a time to find the culprit .
Just remember the culprit can be a bad switch or bad wires between switches .
With all of the yellow wires unpluged there should be no continuity to ground at any plug
If there is then there is a short in that section of wire.

 

[tkos115]

Take the blower housing off and pull the kill wire off
Remove the spark plug and check that you get continuity too ground in the off position and open circuit to ground in all other positions including when cranking .
If this is not the case then either the kill wire is shorted to ground some where or a switch is shorting it to ground.
As for the latter the most likely suspect is the PTO or brake switch .
Like Dorothy following the yellow brick road, you need to follow the yellow wire
In both the cranking and the running positions the yellow wire should always be open circuit to ground
The yellow wire goes to ground to kill the magneto spark
The safety switches are primative sliding contact switchs and regularly go bad

The easiest way to test them is to bypass them by unpluging then bridging the other pair of wires ( orange ones ) which are the cranking circuit
If the mower fires up as it should then plug them back in one at a time to find the culprit .
Just remember the culprit can be a bad switch or bad wires between switches .
With all of the yellow wires unpluged there should be no continuity to ground at any plug
If there is then there is a short in that section of wire.

I do get a ground in the off position with the wire pulled when I check it. It remains an open circuit in all key positions until I hold it in the crank position. If I back the key turn off maybe .20in the spark comes back and works fine. If I turn the key that .20in again when cranking it goes away and the wire is grounded again. It seems like it's the ignition switch, but it does that on both switches so maybe they are both defective? It may be even less than .20in that I have to let the key turn back from full crank but it's a very tiny amount.

 

[bertsmobile1]

Congratulations now you have made my brain hurt to.
First question
Have your tried it with the safety switches jumped on the orange & yellow open like I asked ?
Second is the seat switch a simple 2 pin switch as shown in the diagram ?
Third question is there a relay installed on the yellow wire any where ?

 

[tkos115]

Yeah, I did jump the switches and the seat switch is just a two wire. I didn't find any relays anywhere. Just a 15amp fuse for the main power going to the switch which is good. (Red wire)

 

[StarTech]

Yeah, I did jump the switches and the seat switch is just a two wire. I didn't find any relays anywhere. Just a 15amp fuse for the main power going to the switch which is good. (Red wire)

Just note here the starter solenoid used is a relay (contactor). Just depends industry you familiar with.

It appears that you don't understand the kill circuit operation. In the yellow path. The brake switch must be open (Switch depressed), The PTO will be in open position in disengaged position. The seat switch must be open (switch depressed or operator on seat). Note: The parts list does it being wired the same as the brake/clutch switch which is incorrect. It contact positions is drawn backwards. The seat switch is common to both the brake switch and PTO circuit magneto kill circuit.

Anyways what you are describing is defective ignition switches or the you have the wrong ones. Are you trying to after market or oem switches? It should never ground the magneto in start position. I do know that Oregon 33-383 is the same switch as the Murray 92556 (superseded to Briggs 092556MA). I have tested the in house new Oregon switch here and it does not short out the magneto in start position.