Lasalle starter relay

[KC Tom]

My 1940 Lasalle has developed a problem.
I believe the relay is faulty and the feature that prevents the starter from engaging while the motor is running has become defective because the car starts just fine but if I go for a 15 minute drive and shut it off the starter is completely dead for about 15 or 20 minutes. I have been told that this feature can be disabled by running a wire from the regulator armature to the ground side of the relay.
I am also told that the ground connection on the relay Is a blue wire but I am certain that I have original wiring the the wires are not color coded.
My question is how can I tell which one is the ground side?
I check continuity between each connection and ground but the both have continuity with battery disconnected

[wheikkila]

On your LaSalle starter. It sounds like you may have a bad connection. On the wiring you should have main power. Then two small wires. Looking at the starter. The right wire goes to the push button. The left wire goes to the generator. This is the wire that stops the starter from engaging when running. This maybe were you might want to start. The wires are not color coded like you think. They are colored by thin lines and dashes. If you don't have one. You should purchase a wiring schematic.
                Thanks Wayne     

[35-709]

https://classiccarwiring.com/products/1940-lasalle-40-50-52-v8-color-wiring-diagram
Me, I would prefer the larger one, easier on the eyes.   
Good luck with it.
Geoff N.

[harvey b]

Check the voltage regulator,that is usually where the trouble with the starter comes from.check the points in the regulator to see if they have stuck together?.possibly give it a tap with a screwdriver,that sometimes works,I had a weak starter on my 37,i had to replace the relay on it and i took it apart to clean it up and made sure the wires were nice and tight,it made a lot of difference when i did that. harveyb

[KC Tom]

Hi Harvey
I ran a wire from the relay to the armature on the regular that several people have suggested but it made no difference. I have been thinking the regulator might be suspect. I'll try rapping it. I have a new one that I should put on it. The original one  looks like it had been beat on.

[KC Tom]

Just installed a new regulator and it seems to be working

[KC Tom]

I have come to the conclusion that the starter on my Lasalle is not original to the car because I bought a NOS that art number match's s 1940 Lasalle but is completely wrong. I believe it is off a newer Cadillac. Is that possible and if so how can I tell what year it is without taking it off.

[Joe Jensen]

There should be a tag on the starter like the one I attached for my '49.  In my MPL it shows P/N 1107931 for 1942 - 1948.  1949 is 1107945.  My Master Parts List doesn't show 1940.

Good luck!
Joe

[39LaSalleDriver]

The starter for a 1940 LaSalle should be a Delco 1107912.