Cold Start Wiring Diagram

[Harry]

Dadjimmit.  There was a post just the other day where someone was requesting a wiring diagram and was provided one.  It included a hand drawn version that was declared incorrect.  But there was another hand drawn diagram that was regarded as correct.  Now - I cannot find the post (already!).

Can someone point me to that please?  And tell me what you searched for.  I have marginal success with our search engine.

Thank you,
Harry

[Jonny B]

Go to the search function, if you use the one at the top right under the club logo, be sure to search the entire forum. If you use the search that is fourth from the left in the line of items starting with "Home"

In the search field type: "wiring diagram" cold, the quotes around "wiring diagram" will limit to that phrase, then by adding cold it will search for the word.

I tried it and got 1 page of hits.

Good luck.

[BobH]

Hello Harry, have a look on here, but please note that i believe 230's may be different from 280's and US cars may be different again, and auto/manual cars may also differ

https://www.sl113.org/forums/index.php?topic=35052.0

Did you look in the Tech Manual?, no wiring diagrams, but a detailed explanation

https://www.sl113.org/wiki/Engine/ColdStartValve

[Harry]

Thanks to both of you.  BobH provided the exact post I was looking for but I will also play with the search function some more.  Just seems like it often returns a lot more information than I'm after and I have to sort through everything.  Probably need to refine my searches.

Let me also ask about the TTS.  If it is marked as 20 C/ 9.5 s, the Tech Manual says that means it takes 9.5 s to open at 20 C.  Since it is immersed in coolant, the temperature of the coolant can influence that time longer if the engine is cold or shorter if the engine is hot - correct?

Thanks again,
Harry

[BobH]

I'm no expert, but as i understand it the contacts remain closed for 9.5 seconds during turning the engine over (cranking) when the coolant temp is 20 degrees C.  When the coolant is 35 degrees C or higher then the contacts remain open, so the engine doesn't flood.  The duration is set and doesn't vary with temperature

This may also help if you haven't seen it

https://www.sl113.org/wiki/Engine/ThermoTimeSwitch?action=download&upname=W113%20Cold%20Start%20Thermo%20Time%20Sensor%20Alternative%20rev%201.pdf

Also found this on the web, not sure what car it's referring to, but it's a simple explanation

"Here's how the cold start valve/thermo time switch works:

The thermo-time switch has a metal contact arm inside which is wrapped with a heating element. When it's cold, the arm contacts a ground connection. When you turn the key to start (the cold start valve ALWAYS receives power when the key is in start, and ONLY when the key is in the start position -- temperature is irrelevant as far as the cold start valve itself is concerned) 12v is sent to the cold start valve. If the thermo-time switch is cold, then the thermo-time switch grounds the cold start valve, allowing it to inject fuel. When the key is "on" the heating element in the thermo-time switch is warming up and slowly bending the contact arm, and so once it gets warm enough, it breaks contact and no longer grounds the cold start valve, shutting it off.

However, this applies only when cranking. The cold start valve never receives 12v when the engine is running, i.e. when the key is in the "on" position, only when the key is in the "start" position. So, to answer your question, no, the cold start valve is probably not staying on, unless you've got some weird wiring.

And the thermo-time switch does not supply 12v to the cold start valve, it merely supplies a ground for the cold start valve."

[Harry]

This is fun, actually.  So here is another question based on the wiring diagram provided and the components present in my late 230SL.  When power is provided to the cold TTS, the ground is provided to the Time Relay (TR) and from there power is provided to the CSV.  But, the TR also includes a warming circuit and after 1 second, it lifts the ground from the TTS and the CSV is disabled - even though the TTS is still providing a ground.  (I suppose this is to prevent putting too much fuel into the engine.)

You can continue to crank until the TTS gets warm enough to lift its ground after which you will no longer benefit from the CSV.  The whole thing, if I have it correct, is interesting and suggests a starting procedure that might be better if cranking the engine was limited to short "bursts" or certainly not cranking for long periods.

And the fuel enrichment solenoid, which is fed through the Starting Relay, continues to provide a richer fuel mixture through the fuel injection pump all during the starting process - cold or hot engine.  (It appears.)  Unless the Starting Relay also has a time period of after which it no longer powers the solenoid.  That doesn't appear to be the case?

Thoughts?
Harry

[ja17]

There are two versions of starting aids on the 230SL. We really need to know what version you have before we can help with any starting issues. The two versions for the 230SL are identified as Type II and Type III in the BBB. (Type  I was never used on any W113 cars, just on some early MB sedans, cabs and coupes). Type II is unusual, since it was used on the early 230SLs and a lot of those were later changed to type III as an upgrade. The description of type II and III is in the technical manual and early BBB.

[Harry]

Hi Joe,

This is a late 230SL (1966).  Based on what I see under the Engine Starting Aid Tour, this appears to be Type III since there is no Thermo-Switch.  However, the car does have the "Time Switch aka Time Relay" and the Tech Manual says those were used on "some early 230SL models".  That is part of my confusion relative to having a time delay in the same electrical circuit provided by the Thermo-Time Switch (which this car also has).

A perplexing thing to me is the Thermo-Time Switch and the Time Switch (round canister relay).  The Tech Manual says that both provide an interval over which the ground is provided.  It looks as though the TS imposes a 1 second operating window for the Cold Start Valve and the Starting Relay (powering the Fuel Enrichment Solenoid).  So no matter the state of the TTS, the CSV and the FES will always operate for only one second.

If the engine is hot (and the TTS ground open), neither will operate.

Is this correct?  Probably more to it than I am seeing at this point.

Harry

[BobH]

  The duration is set and doesn't vary with temperature

So the more i read, about the cold start system, it makes me think this statement is incorrect, what i don't understand is how the coolant temperature can affect the signal duration, either the contacts are closed, when cold, or open when hot, i thought the duration was set by the TTS, ie the heater coil opening the contacts after a set time

[Harry]

BobH - I think ultimately, that is correct but remember that the bulb enclosing the bi-metallic strip is immersed in coolant.  So the colder the coolant, the longer it would take the strip to heat up.  The warmer the coolant, the shorter amount of time to heat up.  At least that's what would seem to me.

[BobH]

So, i guess that the TTS is set at 9.5 seconds, designed to operate when cold, so during cranking the contacts stay closed for only 9.5 seconds.  if the engine warms slightly, and is then turned off, after a short trip up the road, when the engine is cranked again, it may open the contacts before the 9.5 seconds if the coolant has warmed, until the contacts stay open permanently when the engine reaches normal operating temperature.  The coolant temperature cannot extend the signal duration, only reduce it.  I can't see it makes any difference, as the CSV only receives a +ve supply when the key is turned to the start position, not during normal driving

[Harry]

I think I finally get it.  Power to the Cold Start Valve and the Enrichment Solenoid is provided through the Starting Relay.  On a cold engine, ground for the magnet in the SR is provided by BOTH the Time Switch AND the Thermo-Time Switch.  The TS drops out after one second and the ground continues to be provided through the TTS until its contacts have heated up and open.  So on a cold engine the ground ultimately comes from the TTS.

Once the engine comes to temperature and the TTS ground is lifted, the TS continues to provide ground for 1 sec at start-up allowing the ES and the CSV to operate very briefly.  At least it appears that way to me.

What a puzzle!

Joe - thoughts?

Harry

[ja17]

You got it Harry. It is complex. Even though I wrote most of the "starting tour" I have to review my notes to refresh my memory on version III. The next version, IV is a little easier to understand. It is amazing how important the function of the time relay (round 1 sec.), is for good starting. You can open them up and clean the contacts and even adjust the duration time if needed.
At temps above 95f or 35c, the duration of both starting aids is set to one second, since the TTS drops out of the mix and the one second relay provides the only ground to the starting aid relays.

Also, remember that the Thermo Time Switch (tts) is affected by time and engine coolant temperature. As soon as the starter is energized, the current begins warming the electrical coil in the tts eventually the bimetallic spring opens the contacts. This duration in time varies depending on engine coolant temperature, since the sensor is surrounded by engine coolant. Engine coolant temperature varies depending on ambient air temperature and residual heat from the last engine run cycle.

[Harry]

Excellent.  Very satisfying to have a grasp on this complicated but ingenious approach.  Thanks everyone for the help!

[Benz Dr.]

So, i guess that the TTS is set at 9.5 seconds, designed to operate when cold, so during cranking the contacts stay closed for only 9.5 seconds.  if the engine warms slightly, and is then turned off, after a short trip up the road, when the engine is cranked again, it may open the contacts before the 9.5 seconds if the coolant has warmed, until the contacts stay open permanently when the engine reaches normal operating temperature.  The coolant temperature cannot extend the signal duration, only reduce it.  I can't see it makes any difference, as the CSV only receives a +ve supply when the key is turned to the start position, not during normal driving

9.5 seconds would be a very long burst of fuel coming from the CSV so it would need to be very cold outside for the system to operate that way. One or two second burst is more typical. Sounds like everyone understands how it works now.

[Harry]

Good point as well.

[Harry]

Well - based on the tests provided in the Tech Manual and my new understanding of this system, it appears my TTS is done.  I get voltage at the CSV for about 2 seconds then it is lifted.  If I ground the TTS, the CSV continues to get voltage until I disconnect the ground connection.  So I need to either build a manual bypass for the CSV or replace it.  It sounds as though these are no longer available?  And the Porsche CSV 92860510102 is available and works in the 230SL.  Can anyone attest to this successful transplant?  No issues?

Thanks as always,
Harry

[ja17]

You can test your tts by cooling it first in your refrigerator.  while still cold, ground the brass Body of the tts (-12v), and connect + 12 v (power) to the "g" terminal on the tts. Output of the "W" terminal on the tts. should show show -12volt until the coil in the tts warms and the contacts open, then no ground is present. The -12volt output of the tts is one of the signals for the starting aid relay to activate.

[Harry]

Thanks Joe.  When I remove it, I may do that for posterity.  But I connected a ground wire to the W terminal of the TTS and the CSV continued to get voltage during cranking.  Then I put the distributor cap back on and tried to start the dead cold engine, and it fired right up.  It hadn't been doing that before.  So I think I'll order the Porsche unit but I thought I might confirm positive experience here with that unit.

Thanks very much,
Harry

[ja17]

Connecting a ground to the W terminal will cause the CSV to activate regardless whether the tts is bad or not.  Most likely your CSV relay is not functioning.

[Harry]

That might be better.  But are you referring to the Time Switch (20)?  Maybe I should remove it and test it.  I had cleared it as acceptable because the  CSV was getting power for about two seconds, then it would drop out.  I had assumed that because that was the case, it was good.

Harry

[ja17]

I would definitely check the round time switch also, but is sounds like it is working. Check the larger starting relay since both starting devices should activate for at least on second when the starter is activated, no matter what the temperature. (not the case with version IV). With version III, the one rectangular relay and the one round time relay, control both starting devices simultaneously . Check to see that you get power to both the CSV and the large starting solenoid on the injection pump, for at least a second, every time the starter is activated. If everything checks out then you could need a tts.

[Harry]

Thanks Joe.  I will certainly check to see that the starting solenoid is getting power.  I appreciate all the help from you and everyone else.