Technical Pre-War Delco Starter Solenoid Help Needed

Good day all. I am looking for some help getting a "mystery" starter solenoid to function so I can see if my '41 Cadillac flathead is worth the trouble to revive. I got one of those "too good to pass up" calls last summer and dragged this old girl out of what would have been her final resting place.



She finally made it into the shop this weekend and after some cleaning, oiling and massaging it would seem she has some potential. Trouble is after overhauling the starter and getting all the individual parts to work, the solenoid still won't pull in to spin the starter. It is obvious by the evidence that someone has preceded me inside the solenoid cover and with it refreshed and assembled as it came apart the low current relay closes but the solenoid coil never gets voltage.
I posted this question over on the Cadillac and LaSalle Club board and to add to the dilemma, nobody over there can identify what my solenoid belonged on when it was born.
Here is a link if you are interested. http://forums.cadillaclasalleclub.org/index.php?topic=145067.msg361545#msg361545

 

I have a couple reference documents and a hand sketch of what my solenoid looks like and I just can't see how I get from "A" to "B"? Anyone out there recognize my solenoid or have any good advise to make mine work? The red bars in the sketch are pieces of fiber board insulation. The "hot" end of the "shunt?" coil in the solenoid windings was poorly soldered to the square metal washer under the head of the starter field coil lug which didn't help so I removed it. The upper "mobile" half of the relay contact is electrically the same as the relay mount frame, which is electrically isolated from everything else. It seems if I create a high current ground connection to that frame the relay would complete the solenoid coil circuit, but there is no evidence that connection ever existed, which may mean nothing since this is the wrong part number solenoid for this starter. This solenoid does have all the required pieces though, IF I can figure out how to combine them.

 

I wonder if that could be replaced with a later solenoid, like a Corvette one:

 

what would it take to make the solenoid you have, be wired as shown in the manual pages? Looks like you have the starter and battery connections reversed?

 

Hey Jim, I have read nearly every thing you have posted the past couple years. Thank you for the response.
You are correct, the solenoid I have was built with the coil connected to the outboard main lug as it sits on the starter in car. The inboard main lug connects to the starter field coil with a copper bar. I suppose I could replace the bar with a cable to the outboard connection and connect the battery to the inboard connection, solder the shunt coil feed to the stationary relay contact and then build a metal sleeve and washer to bond the new battery main lug to the relay frame which electrically would match the reference diagram, If I haven't missed something. It will just look a little funny. If the engine runs and I don't find any other "fatal flaws" then I could eventually buy the correct solenoid.

 

Those sure look close dimensionally. I am sure that was what someone was thinking when they tried to make what I have work. They just gave up before they succeeded.
I apparently can still buy a 1942-48 solenoid which is supposed to function correctly, the 37-41 units were prone to relay failure and are apparently pretty rare now.

 

So after another sleepless night trying to fully understand what all these pieces do I think I might have it figured out. One thing I could not get my head around was what happens to the solenoid coil voltage when the start contacts close? I now believe that is what the shunt coil is for. The main coil closes the start contacts and throws the Bendix and then the smaller current coil just holds the plunger in place until the relay opens.
If I can bond the proper main lug to the relay frame without shorting it to anything else I think this unit should work.

 

The solenoid in your picture is a Autolite/Prestolite solenoid, it wont work on a Delco starter, the plungers are different for one, it just wont work. The correct solenoid for your starter is Delco #1108019 or aftermarket Accurate solenoid #8-903. Gimpy is correct you could replace it with Delco #1119784 Accurate aftermarket 7-929 if you still have the correct plunger.

 

have you cleaned the points faces ??? being its 6 v it needs a super clean surface on them for the amps you need to engage everything . on older equipment we used a simular selinoid on them and often this was the problem when it sat outside for a while unused . often we would clean them and they would fire right over .

 

Hmm, that would explain the inability of the guys over on the CLC to identify my solenoid. Thank you for saving me a bunch more hours thinking about what I did wrong after it didn't work. Out of curiosity, any idea what is the difference with the plungers? This one does seem to bolt up and have about the correct stroke on the plunger when you move it by hand. Am I reading your reply correctly, that I need the original plunger because they are not included with a new solenoid?

 

Thanks for the input Stimpy, I did clean the relay contacts with a point file while I had it apart and confirmed they make good contact when the relay coil is energized. Anybody need a fully functional Autolite SS 4706?

 

I would see if you can get a Delco solenoid on it.

 

This is what the correct Delco plunger looks like. Plunger is not included with the solenoid as it is considered a part of the starter. Your plunger may be correct on the starter but was not correct to work with the Prestolite solenoid.Hope this helps.

Sent from my SAMSUNG-SM-G890A using The H.A.M.B. mobile app

 

And cross your fingers that you have the correct plunger. I had to make the last one that I needed.

They are not just lying around everywhere....

 

Yea, mine is the square back one that probably was on the car, or tractor, or whatever the solenoid came from. I have Googled the part number and closest I can get is a 4705 or a 4707 that were used on a bunch of "other than big three" plus a few Chryslers after the war. I guess it's time to call in a favor from one of my hoarder acquaintances.
Any chance you wrote down the dimensions on that plunger you made? I have a lathe, sort of.

 

It was 15-years ago. I will poke around and see if I can locate one.

 

Well, I had some time to think about this while working out of town for a few days and decided to give the Autolite solenoid rewire a try as I wasn't able to find anyone locally with a Delco I could borrow. After some though I believe the SS4706 I have must have been built for an engine with the starter on the left rather than on the right side of the engine like my Cadillac and most GM stuff.
I found a diagram of a 4000 series Autolite in the same Motors Manual that had the Delco information and the two are electrically identical so I "repaired" what I assume the previous professional had modified, swapped function of the two main lugs and installed it. When I got this car the seller claimed it has sat in the field behind Grand Ma's house since the 60's or early 70's. I had been adding MMO to the cylinders for a while now so with cleaned and gapped plugs and a nurse tank of gas connected I gave her a crank and the old girl fired up and idled at about 500 until the gas was gone. Time for coolant.
For reference, if you need a temporary fix for a bad pre war relay type Delco solenoid and can find a complete Autolite of similar dimension, with the plunger, it can be made to work until you find the right parts.

 

Good luck !