What does the 1 sec. Timer switch, switch?

[Paul99]

So the round canister timer switch.  What does it actually switch or activate and why only for one second ?  The starting tour tells me how it works but can't find what it actually activates.

[wwheeler]

In the starting tour, Look at the first chart Version 2. The middle column talks about the timer and is in the Starting solenoid column.

They changed versions three times during the W113 production. Gets confusing to remember. Good thing we have the chart.

[Paul99]

Great thanks. So the round 1 sec device only affects the solenoid on the back of the injection pump. ?  Or anything else?

[BobH]

Hello, the 1 second timer switches a ground to the cold start relay, which in turn switches a +ve to the mixture control on the injection pump and the intake starting solenoid (CSV) whenever the engine is cranking, regardless of the engine/coolant temperature

[Pawel66]

The names such as Cold Start Valve are misleading. It works during warm start as well.

[Paul99]

great thanks.  I think the Timer switch could be the route cause of a lot of my cold/hot start issues.  I tested mine and at room temperature I noticed that the points were not touching. I have adjusted it so they are closed then open when energised after a second or so which I think is correct.

[BobH]

That's correct, normally closed contact breaking after 1 second. You've probably seen this write up if you've fixed yours, but if you need it:

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

I'm not sure it will help with the cold start, as the thermo time switch is the main component for cold starting.  If you have problems when hot or cold, perhaps the relay or the CSV needs attention

[Paul99]

Yes thanks. Cold starts are perfect, just hot starts are the issue but the fix/adjustment to the timer should help.

It is amazing that these cars seem so complex by comparison. My friend has an MGB which just has a choke you pull out and push back. Simple.  We seem to have about four separate "chokes" depending on if its cold, hot, sort of hot sort of cold and in-between!   

[wwheeler]

We seem to have about four separate "chokes" depending on if its cold, hot, sort of hot sort of cold and in-between!

That made me think how these systems compare to carbureted systems. The biggest thing on Mercedes is that these are all automatic. No action required. I would have originally thought the WRD warm up thermostat would be the choke. But that is really more like the fast idle cam on a carb. More air and more fuel and faster idle RPM. A little bit like a thermostatic choke because it also makes the mixture richer when cold. The starting solenoid would be like the choke as its sole function is to make the mixture full rich when starting.

The cold start valve would then be the pump on the carb that injects fuel into the carb via accelerator pedal. And why you pump the pedal on a carb engine. Pumping the pedal on an injected engine only opens the venturi butterfly. Some of these injected systems overlap, but basically mimic carb systems.