WARNING: 123 Distributor & the "spring"

[awolff280sl]

When checking the rotor on my 123 distributor for wear I found that I could push the rotor down 5mm or so and it would bounce back. Recognizing that this vertical play was not normal I pulled the 123 and found serious wear between the drive dog and the bushing above it. As you can see in the picture there is now a gap between the drive dog and the bushing.
This is undoubtedly the result of too much upwards pressure from the spring between the drive gear and the drive dog.
The spring I used for the 123 in the photo is next to the original MB spring for the original distributor. I believe that it conforms to the generally accepted consensus on the forum (twice as long with about twice the windings, 1mm diameter wire, 9.3mm wide) as a good substitute for the original spring when using a 123, I really cannot tell any difference between the two springs in terms of "compress-ability" by grossly squeezing them. The windings on the substitute appear slightly more seperated.
Note that the part of the bushing on the 123 that has worn away is the conical taper that abuts the drive dog. The corresponding bushing on the original does not have this conical taper.   
I am getting another 123 as well as seeing if I can get this one repaired. No more spring for me.
I suggest that anyone who has a spring under their 123 should pop their distributor cap and do a "push down test" on the rotor. 

[PeterW113]

Andy,

Thank you for this post as it is of great interest.  Last Christmas my present to myself from all was a 123 (vacuum take off model) and this Christmas i intend to fit it whilst carrying out a few maintenance jobs. The "do you - don't you" fit it with a spring has been mulling over in my mind for a while.  I read somewhere that 123 themselves said "no spring" and it looks like you have spotted why.

I am sure the great spring debate will run, perhaps a survey amongst other owners would be interesting, though no wish to create a divide amongst us.

All those with spring say "Yes" and those without  "No"

In the weight of this evidence I will go No!

Regards to all

Peter

[stickandrudderman]

great post, thanks awolff280SL

[66andBlue]

Andy,
what is the news on your repair and how is the new one holding up without the spring??
Have you received any feedback from the company concerning this problem?

[awolff280sl]

Alfred
I have not pursued repairing the worn 123, it's still sitting on my shelf. When I purchased it from Brooklyn Motorwerks back in 2012, they told me to forget the spring and that it was not needed.  I went ahead and added the spring sometime in 2013 after reading Pagoda Notes which suggested that it was needed. When I get around to it, I will call the company in Holland since they are the only ones that I would feel comfortable with the repair.
In the meantime there's been no wear on that bushing on my 2nd 123 without a spring in over a year. My car is a daily and long distance driver and runs great.

[66andBlue]

Thanks Andy!
Put my 123 in today without the spring!

[Tyler S]

Alfred, Any difference in the way the car runs after the install to report?

[Jonny B]

Tyler, thanks for asking the question, I was wondering the same.

[Tyler S]

Jon, I drove his car around the block after the install. Ran great! But I had never driven it before so nothing to gauge.

[66andBlue]

Well guys you need to be a bit more patient. Only drove the car home from Tyler's place in stop and go traffic and did not notice any difference, that is, it did run very well. This car is an automatic with the 3.27 axle, so in slow traffic I just keep it in 3rd gear.

[Atazman]

Interesting info!  Just wondering about us guys that are using the original spring (from old distributor installation) with the new 123 distributor??  I will have to check my rotor movement to see if things are wearing.

My records show that I was told to re-use the old spring by a 123 representative.

Thanks for sharing about this.

[Benz Dr.]

I was under the impression that the spring is there to help keep the drive gears tight. I honestly can't see how a little spring would wear anything that much but clearly something happened.

 There are a number of shims and a fiber washer between the drive collar and the housing on a Bosch distributor and they tend to last forever. I've seen fiber washers wear away which can result in a fair amount of end play but it's generally lest than 2 or 3 mm. Maybe a lighter spring is in order.

[Tyler S]

Dan, I think you are right. Without the spring the distributer drive gear will want to walk itself up. I also noticed that when installing Alfred's 123 that the distributer housing doesn't sit completely flush with the base. If the OP has it pushed down all the way then this could explain the wear. When the shaft gets hot and "grows" with no clearance, it will start eating itself. This is just a thought.

Alfred, this is something we should double check.

[Peter van Es]

I've been running a 1-2-3 without the spring since installation, 5 or so years ago. Works excellently, love my 1-2-3.

Peter

[hauser]

Andy, thanks for sharing your findings.  Your problem has saved a few others' 123 from the same fate.  As for me this couldn't have come at a better time during my resto / preservation at SL Tech.  I haven't heard Gernold speak of this problem.  I don't know if he installed any springs on any 123 swap he performed.

[awolff280sl]

Seems that I am still dealing with the fallout from excessive upward pressure of my 123, probably the result of "the spring":
Have been having intermittent starting problems, traced it to no spark, checked the 123 distrib, Sure enough, the spring-loaded pin in the center of the cap was completely worn away.
A new cap and rotor solved the problem.
So, I should have changed the rotor when I first identified this spring problem a year and a half ago. It is recommended to change the cap and rotor every 15-20,000 miles, and I had about that much on this cap, but the wear appears excessive.
Fortunately I didn't get stuck anywhere.