Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: Harry on January 05, 2023, 16:30:33
-
I am reposting this after getting some clarifications and corrections from Joe and Bob. Thanks again to each of you.
After studying the wiring diagram for a later 1966 230SL (Version III) and hearing from others on this forum, I think that I have captured the gist of the Starting Aids for this car. I am posting it for future reference here perhaps in a more clear and succinct manner for those who may be early in trying to understand the approach used by Mercedes. I made a labelled excerpt from the wiring diagram that I believe supports this summary, but I am always happy to hear from others to achieve factual accuracy.
I did not elaborate on how the individual components that make up this system operate since that is provided in the tech manual.
Involved components
Starting Aids
1- Cold Start Valve (CSV) 31
2- Fuel Enrichment Solenoid (ES) 33
Supporting Electronics
3- (Ignition switch/starter)
4- Thermo-time switch (TTS) 32
5- Time switch (TS) 20
6- Starting Relay (SR) 21
How It Works
When the ignition switch is turned and held in the Start position, 12v is provided:
- To the Time Switch (20) – provides a ground to the SR for about 1 second
- To the TTS (32), - provides a ground to the SR for about 9 seconds (on a cold engine), and
- To the electromagnet of the Starting Relay (21) – when ground is provided, provides power to the CSV (31) and ES (33)
The Starting Relay (21) electromagnet closes the primary circuit of the relay sending the 12v from Fuse 6 to both starting aids – Cold Start Valve (CSV) (31) and Fuel Enrichment Solenoid (ES) (33). But - for that to happen, the electromagnet in the Starting Relay (21) must be grounded.
This ground circuit for that electromagnet is simultaneously provided through both the Time Switch (20) AND the TTS (32). But the ground circuits are only temporary - so those start aids will only operate for a brief period with each start attempt.
When the Time Switch (20) receives its 12v from the ignition switch, it drops its ground after about a second or so. After the ground from the Starting Relay (21) is lost, the ground from the TTS (32) is still provided to the Starting Relay (21) and both start aids will continue to operate.
When the TTS (32) also receives the 12v from the Starting Relay (21), it drops it ground, but in about 9 seconds. (The duration of time the TTS requires before it drops its ground connection is dependent on engine temperature. A cold engine will take longer to drop ground than a warmer engine.)
When both grounds to the SR are dropped, the starting aids are no longer powered.
So – since the TTS operates for the longer period of time on a cold engine, it is the dominant factor in starting a cold engine and will provide starting aid support for up to about 9 seconds. (Multiple start attempts may have a shorter application of the aids since the TTS will have been warmed up on prior attempts.)
An engine that is already at running temperature will not benefit from the TTS (32) ground since it will already have been dropped by the warm engine temperature. Under those conditions, the TS (20) will continue to operate (for about a second) and becomes the dominant factor in starting. As a result, the CSV and ES will operate very briefly even on starting an engine at running temperature.
-
Harry
Great. Thank you for the work.
-
Absolutely. Thanks to those on the forum who helped me to better understand. It is certainly not intuitive!
-
Thank you for thorough explanation. My 64sl has a cold start problem.it seems that the cold start solenoid works.No problem with warm start. I had a groun problem detected by windshield wiper malfunction which I solved by creating a new god on the wiper motor. Could these two problems be related? If so should I make a new god for the cold stat problem? Thanks Martin
-
Hello Martin, when you say the cold start solenoid seems to be working, do you mean the solenoid on the cold start valve? Can i ask how you know it's working?
If it's working electrically, then i wouldn't think you have a ground/earth problem, but there may be a problem inside the valve, the plunger/pin may not be engaging, or there could be a fuel blockage, i think there may be a filter in there, or the spray nozzles may be blocked
There's a detailed write up in the technical manual, under "engine starting aid tour" but you need to be full member to access it. If you're going to maintain your car it will be invaluable and well worth the tiny fee to join
Please do let us know how you get on
Bob
-
I am reposting this after getting some clarifications and corrections from Joe and Bob. Thanks again to each of you.
After studying the wiring diagram for a later 1966 230SL (Version III) and hearing from others on this forum, I think that I have captured the gist of the Starting Aids for this car. I am posting it for future reference here perhaps in a more clear and succinct manner for those who may be early in trying to understand the approach used by Mercedes. I made a labelled excerpt from the wiring diagram that I believe supports this summary, but I am always happy to hear from others to achieve factual accuracy.
I did not elaborate on how the individual components that make up this system operate since that is provided in the tech manual.
Involved components
Starting Aids
1- Cold Start Valve (CSV) 31
2- Fuel Enrichment Solenoid (ES) 33
Supporting Electronics
3- (Ignition switch/starter)
4- Thermo-time switch (TTS) 32
5- Time switch (TS) 20
6- Starting Relay (SR) 21
How It Works
When the ignition switch is turned and held in the Start position, 12v is provided:
- To the Time Switch (20) – provides a ground to the SR for about 1 second
- To the TTS (32), - provides a ground to the SR for about 9 seconds (on a cold engine), and
- To the electromagnet of the Starting Relay (21) – when ground is provided, provides power to the CSV (31) and ES (33)
The Starting Relay (21) electromagnet closes the primary circuit of the relay sending the 12v from Fuse 6 to both starting aids – Cold Start Valve (CSV) (31) and Fuel Enrichment Solenoid (ES) (33). But - for that to happen, the electromagnet in the Starting Relay (21) must be grounded.
This ground circuit for that electromagnet is simultaneously provided through both the Time Switch (20) AND the TTS (32). But the ground circuits are only temporary - so those start aids will only operate for a brief period with each start attempt.
When the Time Switch (20) receives its 12v from the ignition switch, it drops its ground after about a second or so. After the ground from the Starting Relay (21) is lost, the ground from the TTS (32) is still provided to the Starting Relay (21) and both start aids will continue to operate.
When the TTS (32) also receives the 12v from the Starting Relay (21), it drops it ground, but in about 9 seconds. (The duration of time the TTS requires before it drops its ground connection is dependent on engine temperature. A cold engine will take longer to drop ground than a warmer engine.)
When both grounds to the SR are dropped, the starting aids are no longer powered.
So – since the TTS operates for the longer period of time on a cold engine, it is the dominant factor in starting a cold engine and will provide starting aid support for up to about 9 seconds. (Multiple start attempts may have a shorter application of the aids since the TTS will have been warmed up on prior attempts.)
An engine that is already at running temperature will not benefit from the TTS (32) ground since it will already have been dropped by the warm engine temperature. Under those conditions, the TS (20) will continue to operate (for about a second) and becomes the dominant factor in starting. As a result, the CSV and ES will operate very briefly even on starting an engine at running temperature.
I've just added this to the tech manual
Peter, perhaps you could have a look and confirm if i've uploaded the schematic diagram correctly, as the instructions for attachments/uploading, are still not that clear to me
-
Done. Bob, please read the following:
https://www.sl113.org/wiki/PmWiki/BasicEditing
https://www.sl113.org/wiki/PmWiki/Images
https://www.sl113.org/wiki/PmWiki/Uploads
and
https://www.sl113.org/wiki/Main/News
-
Hi guys, I'm new to this forum but find it real great.
Does anybody know when the TTS was moved from that waterjacket that also had the temp sensor in it was moved directly to the cylinderhead?
And where in the cylinder head. I was looking for it, but mayby I'm too blind to find it :P
Thanks for any reply
Cheers Karl
-
I don't know when it was moved but on my 1970 it located just below and between spark plugs for 5 and 6 cylinders.