Problems starting a 230SL

[RoyB]

All

This could get long, so bear with me as I want to ensure I have provided all of the details.
My 1963 230SL used to start and drive quite nicely, but I got the great idea to put in an electronic ignition after reading about better starting and no longer needing to replace ignition parts.
I tried the Hot Spark module, which did not work well above 3500 RPM.  A lack of power and back firing were the main issues.  Then I tried the Pertronix module, which did the same thing.  I also installed a Beru Blue Coil leaving the capacitor on the coil. According to the installation documents, Primary Resistance should be over 3.0 Ohms, and I am reading 3.5 Ohms. 
I removed these components, and put in new points and a condenser.  So now both modules are sitting in a box on the shelf.  I did leave the Beru Blue Coil and Capacitor in place.  When putting the wires back into the Distributor, I put dielectric grease on the Fiber Insulating Washers as these items tend to deteriorate over time.  I check continuity with the Ohm meter from the points to the body of the distributor and everything was as expected.  The car ran as expected again, but over time started mis-behaving.  When you try to start the car, the starter turns over the engine well but the engine just cranks and cranks.  If you let go of the key at the right time, the car starts.  Having ridden motorcycles almost all of my life, I hear what the engine is doing and find I can release the key on one of the compression strokes and it will start.  Lucky guesses or whatever, it works but this is not the way it should be.  My first though was battery.  If voltage is too low, the draw from the starter will not allow enough voltage to start the engine.  However, I have just over 11 volts at the battery when cranking, so that is not the issue.  When checking voltage with no draw, the reading is 13.32 volts.  The battery is not very old, but it was tested to make sure.  I installed a new starter that I had sitting on the shelf which is the 1.5 HP version. Remembering old Chevrolets from my youth and their issue with starters drawing too much current and causing dead batteries, this seemed like a good idea.
Now the starter turns over the engine even faster, but the issue is still there.  Hold the key in the start position, and the engine just turns over.  It will start if you release the key at the right moment.  I have installed a new Ballast Resistor, which supplies the coil with the proper voltage (12.3 volts) and verified the resistance (1.3 Ohms) across the leads, so this component is working as expected.
I suspect that the ignition switch may be the culprit and have reviewed that section of the Tech Docs.
Before I start to dig into that, I wanted to see what the group may have to say about this problem and what if any tests can be done to sort out this issue.
As always, thanks for your willingness to respond. 

[RoyB]

After writing this, and thinking about it more, I think I may have a way to test this theory of mine regarding the Ignition Switch.
If I put a starter jumper switch across the terminals of the starter, and turn on the key, the starter jumper switch can be used to turn over the engine.  With the ignition on, the car should start as expected.  Not as scientific as I would like (meaning testing the switch for continuity across all leads while operating the switch) but it may be a good start.

[Pinder]

It almost sounds like you dont get spark in the Start position but do in the run position. did you check if Spark Plugs have spark in the Start position?

[Pinder]

https://www.sl113.org/wiki/Electrical/IgnitionSystem

[RoyB]

I do not see a spark in the start position, but obviously there is in the run position.
The wiring diagram and my thought in the starter jumper switch may get me heading in the right direction.
I will verify the lack of spark with the key in the start position, then try the jumper and the key in the run position.
I like it when a plan comes together:)
Thanks for the schematic for the ignition.

[Pinder]

My guess is that when you put everything back the wire that goes from starter to one side of the balast resistor is ether been left off or its connected to the wrong end of the balast resistor or the same wire you have not connected correctly on the starter.

When in the Start position you should be getting full battery voltage to the coil.   Ive made this kind of mistake before  with similar results. So its likely be one of the above conditions.

[RoyB]

Last weekend I was able to connect the remote jumper across the leads of the starter.  I have the number 1 plug out of the engine, grounded to the cylinder head with the plug wire attached. I had my wife turn the engine over with the key.  There was a reasonable spark at the plug but the engine did not start.  Then I had her leave the key on and I turned over the engine with the remote jumper.
I got a much larger spark and the engine started immediately.
I was not aware that a ballast resistor should be connected one way or the other, so that is worth looking into.
I do have the proper amount of resistance across the leads, which should result in a slight drop in the voltage at the coil.
Thanks for the feedback.

[Pinder]

No i did not mean that it should be connected one way or another. it will work either way its just a resistor.

I mean the wire coming from the starter to the coil is supposed to bypass the resistor such that the voltage is not reduced. if that wire is connected to the resistor it will reduce the voltage if its connected to the wrong end of the resistor. the wrong end in this case is the end that would have voltage flow through the resistor on its way to the coil. What needs to happens is that the wire from the starter needs to go to the coil and not the resistor. on my car this wire was connected to one end of the resistor and on the same end a  wire is connected from there to the coil. basically the resistor is in this case being used as connecting point only and not to reduce voltage. Hope that makes sense.  My car is a 1970 280SL and wiring maybe different but is trying to achieve the same thing in that when the starter is cranked full voltage needs to go to the coil. I think your onto something with your latest test.

[Pinder]

from what you describe it sounds to me like the wire that goes from coil to balast resistor is connected the wrong end of the balast resistor. try moving the wire to the other end of the balast resistor.  My thinking is that if you are able to start it in the run position then the run position is giving  full voltage to the coil and that can happen if wire from the igniton to the balast reistor is bypassing balast another words connected to the wrong end of it.

[RoyB]

I am finally able to get back onto this project.  After reviewing the posts, I now have a better understanding of what might be missing.
-----
My guess is that when you put everything back the wire that goes from starter to one side of the balast resistor is ether been left off or its connected to the wrong end of the balast resistor or the same wire you have not connected correctly on the starter.

When in the Start position you should be getting full battery voltage to the coil.   Ive made this kind of mistake before  with similar results. So its likely be one of the above conditions.
-----
I think this post hit the issue right on the head.  I do not have two connectors at the end of the Ballast Resistor.  In looking at the Wiring Diagram, there should be two connectors and I only have one.  I would like to say I inadvertently left off one of the wires, but this is the way the wiring was when I got the car - which has always been difficult to start.  Can anyone tell me what color the connection from the starter to the Ballast Resistor is supposed to be so I can start the search for a cut or missing connection?

[Benz Dr.]

Early cars won't have this wire so don't bother looking for it. Maybe you have a defective ignition switch and if it's an original one you should consider changing it.

[Montreal V8]

  Couple of observations. The factory shop manual (BBB) wring diagram does not appear to show a bypass circuit for the coil resistor while cranking, even on the 280 SL. The most common bypass for other vehicles, was from a separate circuit via a dedicated terminal on the starter solenoid, and certainly not as shown in the above diagram. If wired thus it would have low voltage current supplied to the solenoid, via the resistor,when in the "run" position. On some vehicles, a separate connection was at the ignition switch. Whichever circuit is used, the bypass must ONLY be supplied whilst cranking, and NOT connected in any way to any other circuit.

[Benz Dr.]

I would agree with you on these points. Done right, it's a good mod if you don't have it.

[Montreal V8]

        One way to wire in a bypass circuit would be to use a relay activated by the solenoid circuit. Another possibility, although I have not        tried it, would be to fit a diode in the line from the solenoid to the resistor to prevent feedback to the solenoid.

[RoyB]

Thanks for the feedback.  I was on a similar path as I thought through the connection from the Solenoid to the Ballast Resister. Voltage would continue to be applied to the Coil and the Solenoid when the ignition switch was back into the Run mode.  The idea of connecting to the Solenoid with a Diode or a Relay Switch seems to be the most logical. 

[igor]

Roj, when you put in an electronic ignition be cerful.
You mast also change spark plugs to be adecvate for power of it.
Problem is beceuse electronic ignition give stronger spark and spark plug will be hotter.
It will be great opportunity; spark plug can be broke and small part of spark plug;
ceramics can be cut off and fall into motor!
My frend install it on old VW and live old spark plug and afther feew month later was big problem.

[RoyB]

Problem fixed!  Per the response from Pinder, I wired a relay into the system.  The relay bypasses the Ballast Resistor when starting, allowing full voltage to the coil.  The car now starts much easier.

[Montreal V8]

   Glad to hear the starting problem has been resolved. Only comment I have would be that the connection to Relay terminal 30 may be slightly enhanced if it was connected directly to battery Positive. This would overcome any voltage loss through the wiring harness and ignition switch.      Please note - this is not meant as any type of criticism.    Cheers,  Dale.

[RoyB]

Good point Dale.  The wire from the ignition switch to the Ballast Resistor looks like 16 gauge, which is adequate.
Now that the car starts and runs well, I can get moving on all of the other things that require my attention:)

[Pinder]

Im glad it worked out.