Mandatory Electrical Components to Start a '47 DeSoto

[Bingster]

I'm making certain that my wiring is correct to start my DeSoto. There are a lot of connections that don't seem to prevent the car from starting. But here's what I can deduce from the wiring diagram:

 

• Battery
• Generator
• Starter Solenoid
• Voltage Regulator
• Transmission Relay
• Coil
• Distributor

 

I'm not certain if my ignition switch works so how do I stop the engine if it starts?

 

I'm going to have to start the engine with a remote starter button.  I'm not completely certain where I hook up the leads for that.

[Dave72dt]

You only need about half of those items to actually start it.  If you're going to use a remote starter switch, you may as well use a remote ignition switch, a simple on/off toggle will work.  Your gen, voltage regulator and trans relay do not need to work or be hooked up and a simple jumper  from battery hot to the coil will work for an ign switch.  Use an alligator clip at one end or the other to stop the engine.

[Bingster]

Thanks for the info.  It's getting colder here in Iowa and I am determined to start this thing before it closes in.

[Bingster]

Well, I thought that I had all my ducks in a row and tried to fire up the DeSoto, but no go. I kept pushing my remote starter switch and nothing happened.  I had the large alligator clip on the lower right large terminal and the smaller clip on the upper right terminal above it. Nothing happened when I pushed the remote button.

 

I don't think my ignition switch works but I tried it on and off. Nothing. I traced my wiring and nothing happened until I got frustrated and bridged the two large terminals at the bottom of the starter solenoid. They sparked and the starter spun but didn't engage.

 

Just two weeks ago it did work and turned the engine over without plugs. So here I am wondering if the starter solenoid is bad or something else. That starter was a bear to remove and put back. 

 

I have the + side of the coil going to the distributor. The - side goes to the negative post on the battery. That seemed to be what my diagram said. But I doubt that would have anything to do with the starter not working?

 

Well, who's going to tell me the bad news?

 

 

 

 

[DonaldSmith]

Looking at the solenoid,

Upper right stud:   Yes, that's the one you jump to, to actuate the solenoid. 

Lower right stud:  That's the heavy stud, with the positive cable from the battery.

Lower left stud:  This has a copper bar going into the starter, to complete the starter circuit.  Also, there's a small wire to the Sisson choke, to partially close the choke while the engine is cranking. 

Upper Left Stud:  This has to be grounded somewhere, to complete the control circuit.  Ma Mopar grounded it to the generator, so we can't crank the starter when the engine is running.   With an alternator instead of a generator, we have to ground that post to the engine block somewhere, and remember not to push the starter button when the engine is runninig.  Awful sound.

 

Have hou checked that the Upper left Stud has a good ground? 

 

[Bingster]

The only difference that I have in comparison to the above is that I have my battery negative on the lower right. And although the wiring diagram for the starter solenoid seems to me to be able to be interpreted in a couple of ways, it looks like the heavy black negative wire from the battery goes to the heavy post on the lower right.

 

Now, maybe not.  I did the screwdriver trick and touched the two lower thick posts together, and my starter spun but did not engage?  The know the lower left terminal is the positive ground. At least I thought I knew.  So would the starter spin at all if the thick lower right post was positive?

 

The wiring diagram shows a wire going from the push button inside the car to the upper right post of the solenoid. Shouldn't that wire then be negative? Mmmm. 

 

 

[Dave72dt]

Touching the two heavy posts together will make the starter turn over but it does not push the starter drive into the ring gear.  Power to one of the small posts on the solenoid is supposed to do that.  As that starter drive engages, contact is made internally in the solenoid to connect the two heavy posts, same as what you did with the screwdriver externally.

 

If you touch the small post that has the wire coming from the starter button to the heavy post on the starter coming from the battery, it should engage the solenoid, spin the starter and the engine.

[Bingster]

Thanks. I'll go and give it  shot now.

[Bingster]

I did just that. Bridged the lower right large post with the upper right small post. Nothing. I have no wire on that upper right small post. There's supposed to be a wire coming from the starter button in the car. So I wondered what polarity that starter button had carried to the upper right terminal?

 

There is a guy online who has a seven-part series on this very starter. Pretty great stuff, although he meanders a bit too much. But I didn't hear him say what wire you could attach there now that would make the starter engage. I do think he showed a set of points behind that small upper right terminal.  Somehow that starter button in the car activated those points to make it crank.

 

So that's where I'm at. I thought that perhaps the upper right terminal might need to be grounded because bridging it with the negative battery below it didn't do anything. So I hooked up a ground wire from the upper right post to the battery ground. All I got was a mini-welding screwdriver.

 

So the question is: What goes on that upper right terminal?

 

 

[Los_Control]

My only experience is with old fords .... my Dodge has a stomp starter and no solenoid.

With the old Fords there were always 2 small post on top, one is vacant and for some accessory .... it is the other small post you want .....

You wont hurt anything jumping across the solenoid .... try all configurations til you find the one that works.

[kencombs]

8 hours ago, DonaldSmith said:

Looking at the solenoid,

Upper right stud:   Yes, that's the one you jump to, to actuate the solenoid. 

Lower right stud:  That's the heavy stud, with the positive cable from the battery.

Lower left stud:  This has a copper bar going into the starter, to complete the starter circuit.  Also, there's a small wire to the Sisson choke, to partially close the choke while the engine is cranking. 

Upper Left Stud:  This has to be grounded somewhere, to complete the control circuit.  Ma Mopar grounded it to the generator, so we can't crank the starter when the engine is running.   With an alternator instead of a generator, we have to ground that post to the engine block somewhere, and remember not to push the starter button when the engine is runninig.  Awful sound.

 

Have hou checked that the Upper left Stud has a good ground? 

 

Bingster, pay close attention to the red in this post.   I didn't see where you grounded that post before jumping to the upper right.

[Bingster]

The upper left is connected to the generator.

[DonaldSmith]

Binger said: "The upper left is connected to the generator.'  OK if the generator is OK.  You could try grounding the wire somewhere else,  as a test. 

[Bingster]

Well, the engine turned over a couple of weeks ago.  I've been out trying all sorts of combinations. When I place a screwdriver from the upper right post to the lower right post, I get a spark and a faint click but that's it. 

[Dave72dt]

Check your cables, all the grounds and put the charger on it

[Bingster]

Somewhere there is obviously something wired up wrong.  I'm not completely certain that I have deciphered my wiring diagram successfully.  Simplified for starting:

 

Coming out of the coil the + side is ground going to distributor tang?

 

The - post of the coil goes to the hot battery negative.

 

That is how I reduce all of the wiring coming from the coil in able to start the engine. Which right now it isn't. The other puzzle is the starter solenoid. 

 

From what I can deduce from a guy's in-depth explanation of this very same DeSoto S-ll starter,  the two smaller upper posts energize an upper coil which closes two small points (looking much like distributor points) over the right upper post.  What I do get is that the push button starter switch on the dash sends electricity to that upper right smaller post to energize the coil to close the points.

 

Thing is, with the smaller upper left post being ground from the generator, I assume that the electricity from the dash switch going to the upper right post is hot negative to energize that upper coil.

 

I am told that these two smaller upper posts are a separate operation from the two larger lower posts, with the top two being insulated from the lower.  In effect, I guess, there are two independent solenoids which combine to make up one single solenoid which act together to crank the engine. Ugh?

 

I have tried a combination of bridging solenoid posts and all I can do is spin it. Seems to me that something is amiss elsewhere in the pathway.  I'm just getting into using a multi meter to test circuits and hopefully that will find the problem.

 

 

[DonaldSmith]

The starter solenoid is the entire apparatus that rides horseback on the starter.   The upper posts power the coil that closes the heavy duty connection between the two bottom posts and also engages the bendix drive to the flywheel. 

 

[kencombs]

Have you checked that upper left wire (the one that should go to the generator) to be sure it is grounded?   Or just attach a temporary wire to a known good ground and try it?   I the solenoid pull-in circuit is dead simple, voltage in on one small terminal and out to a ground on the other and polarity doesn't matter for the purposes of a test start.  

[Bob Ritter]

If you are going to check out the electrical system you need to get yourself a Digital Multimeter for circuit testing. With it you could checkout the ignition switch in a couple minutes. They are pretty cheap and easy to use.

[Bingster]

I've got an older one and have been looking at videos learning how to use it.  I don't think the ignition switch even works on the car. 

[Bob Ritter]

Using a Volt Meter is pretty simple, you turn the meter on rotate the dial touching the  ends together until the needle moves. Now that we have juice running through the meter hook the red lead to the center post on the ignition switch with the key on and touch the other two post one at a time. If the meter moves then the ignition switch is good. With the meter you can check the amount of voltage, but lets just see if the ignition switch is working for now.

Best of luck. (rrittere2@ca.rr.com)

[Bingster]

OK

[Bingster]

If the starter button on the dash isn't connected to the solenoid, would it make a difference whether or not the ignition switch was good?

[Sniper]

The ignition switch provides voltage to the coil  The starter button makes the starter work.  Interrelated, but not sure if the ignition switch need to be in run for the starter button to work.

 

Ok, I found a schematic. yes it appears that the ignition switch feed the starter button via the fuel gauge, so if the ignition switch isn't working odds are the starter button won't either.

 

[Bingster]

I do have the diagram, and figured that if I attach direct power from the battery to that terminal where the starter switch fed, it should substitute for the starter switch.