ignition problems

[Joe]

The car has a 280SL engine, but I don't know what year it is.
1. With the points closed, I get about 8.5V at the + side of the coil. With them open, it registers 12.1V. What does this indicate is bad?
2. There is what appears to be a capacitor attached to one coil mounting bolt. It is large and has a heavy ground wire descending from its bottom and connected to the frame with the battery ground. The small wire from the top of the capacitor is just hanging. Should it go to the + side of the coil? Was this something a DPO added?
Thanks for the help!
Joe
1965 230SL

[jeffc280sl]

Hey Joe,

Have a look at the tech manual here:

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

Let us know if you have any additional questions.

[al_lieffring]

What you would be testing by doing this is checking the voltage drop across the balast resistor. This test doesn't realy have any diagnostic value other than showing that the coil is drawing current when the points are closed. Buy a new set of points (Bosch if you can get them) and condensor and replace them. Cleaning the points amd/or resetting the dwell in my experience is a temporary repair only for getting a car to run until the points can be replaced.

The large cylindrical capacator with the braided ground strap is a radio static supressor. And yes the insulated lead should go to the + side of the coil.

[Joe]

The car has a weak spark at the plugs, and across the points. I just put on a red MSC hot coil (0.7 ohm), but the battery had gone dead so I couldn't test it. I am trying to install an electronic ignition, and sort of put things right while doing so. The ballast resistor had gotten broken when the hood spring slipped its holder, but I was able to drive the car anyway. I found I had a new ballast resistor and put that on. The broken one was 1.8 ohm and the new one is 0.9 ohm, but I guess I need the 0.9 when the electronic ignition is installed.
My battery charger appears to have gone south, so I have to replace it. It makes sense to have a well-charged battery prior to these experiments.
More to follow....
Joe

[jeffc280sl]

Hi Joe,

What electronic ignition do you plan on using?

[Joe]

I am installing a Pertronix.
Today was frustrating. I can't find a TTS. I wanted to do the mod that runs current off the G connection to the ballast resistor for enhanced starting.
The numbers on the head are E-9.5 and 130 016 08 01 280 SE/A, which, according to the tech manual, is a 280SL head. The numbers off the block are 130/980-12-029217, indicating a 280SE block, I think.
There is some sort of thermo switch near the top of the radiator, but it has only one wire (brown) going to it. The other end is dangling.
There is a device on what I would call the throttle body that has a place for two wires, but no wires are near it. I found a photo of it on the SLS site, but only the gasket is available. Thinking the name of the gasket might provide a clue to the name of the device, I put the gasket name, Dichtung am Leerlaufschalter, through Babelfish and in English it is "Poetry at the idle counter." This, of course, was quite helpful and has given me much to mull over, such as "are Germans actually reciting poetry when they appear to be clearing their throats?
I got the battery charged and now the engine won't turn over, but the headlights are strong. All I've really done is put in a new ballast resistor. Well, I swore a couple of times, but it was under my breath (and, in English).
Joe Alexander, would you come live with me for a week? The weather is lovely.

Joe Melton
1965 230SL with unknown engine
Colorado Springs

[jeffc280sl]

On the 280SL the TTS is located in the rear of the cylinder head.  There is no device with wiring in my 280SL radiator.  There is a high temperature switch located on the thermostat housing where a hose from the radiator connects to the engine.  The wires connected to the throttle body are part of an emissions system on later 280SL engines.  That's a whole other area to look at another time.  Visit the tech manual and you will find a wiring diagram.  You have disconected a wire going from the ignition system to the starter.

Post some pictures if you can and we can tell you what you are looking at.

[al_lieffring]

If you are wiring up a resistor bypass and using the g terminal at the thermo time switch, that will also require the instalation of an isolation relay.

Connecting the thermo time direcly to the balast resistor will cause the starter to engage any time the ignition is switched on. An easier way to do this is by using the built-in bypass terminal on the starter solenoid.

More than likely some time in the last 40 years, your starter has been replaced  with a Bosch SR 59X and on these replacement starters there is an extra screw terminal on the solenoid specifically for this purpose.

On that starter solenoid there are two screw terminals (#50) the smaller screw goes to the purple wire from the starter switch. The larger screw (#16) is typically not used on a 230sl but can be connected directly with a (new) wire run following the battery cable to the coil side of the balast resistor.

if your car still has the original type starter with only one screw terminal an isolation relay WILL need to be installed.

As for Your starter not engaging, first thing I would check is the shift cable at the reverse light / starter lock out switch, on the firewall between the valve cover and the brake booster. (only on Automatic Cars) Stick shift cars are wired directly from the ignition switch to the starter.

  

[hands_aus]

My early 250 SL has the original starter with no spare contact for the ballast resistor by-pass.
So when I installed the ballast resistor by-pass relay I picked up positive from the start relay on the left side mudguard.
That saved a wire wandering along the plug leads and it looks part of the original harness.

I secreted the modern relay in the space under the bonnet prop base where the resistor is mounted.

The by-pass allows a vigorous engine start even in cold weather.

[Joe]

Yes, the bypass is what I am doing. Its a stick shift.
The starter groans but doesn't turn the engine over. It worked fine till I started trying to get this hard starting problem solved (with installing the Pertronix and the ballast bypass). Now rain and snow are coming and my time is short, too.
There is no TTS, though. I'm pretty sure about that. I'll do a closer search when time permits, but it is not in the side of the head nor on a pod near the injection pump. I'm wondering if this has something to do with the block being from a 280SE (I think it is, anyway).

Thanks for the advice.
Joe

[Joe]

I pulled a TTS off a 280SE engine I found in my warehouse. It was screwed into the head just an inch or so to the right of the #6 spark plug. When I checked that location on the car on which I am working. I found there is a large metal pipe attached to that hole in the head (with two or three adaptors). This pipe comes out and then straight down and under the engine. I didn't trace its path, but I did find the TTS screwed into this pipe 3 or 4 inches down from the spark plug. This doesn't sound like the setup I have read others have, but I am glad to have found it.
We just moved into a new house, and my  wife has put my BBB somewhere out of sight and reach and memory. Can someone tell me the wiring for the thermo valve in the therostat housing and for the device in the throttle body?
Joe Melton
Colorado Springs
1965 230SL w/280SL engine

[glenn]

Clean the ground cable and the starter cable at both ends, the battery terminals and the ground and starter terminal???........

[al_lieffring]

Joe

The pipe you found is a cooling system modification for late 280se/sl engines It was usually dealership installed for lowering the engine tepmperature on cars with air conditioning. The switch on the thermostat cover turns on at 212deg F. and switched on the auxilary cooling fan (on sedans) and advanced the timing 10degrees via the switching boxes. This would would be on 1970 -71 model cars. The throttle body switch is for activating the throttle lift solenoid (automatic transmission cars). So niether of these would have any function on a 280 motor installed in a 230sl body with a stick shift.