Cold Start Valve …. Ongoing problems

[hands_aus]

Hey Group,
Because the cold start valve on my early 250SL is reluctant to consistently work properly, I set up a test lamp on it.

Also I have installed a by-pass switch in parallel to the same terminal.

I watch the test lamp when I start the car for the first time, after priming the system for about 10-15 seconds.

It comes on for about 2-3 seconds BUT it is VERY DULL and the cold start valve DOESN’T operate.

When I press the installed inline by-pass switch, the test lamp comes on VERY BRIGHT and the COLD START VALVE operates.

My thoughts ...

The Thermo time switch works
The relay works

I suspect there either is a semi broken wire in the system that is providing a high series resistance and reducing the voltage available to the cold start valve
OR
Not enough voltage/current is going through the relay contacts to the cold start valve to activate it.

The relay for the Inj Pump solenoid is identical to the relay for the cold start valve.



My Intentions…

   1. remove fuse #4 to the fuel pump
   2. move the gear stick to ‘R’ or ‘4’ , this will stop the car from trying to start but will allow the cold start system to function
   3. use the other relay for the cold start valve and watch the test lamp to see if it shows VERY BRIGHT.
        4. test the resistence of the wire between the relay and the cold start valve.

Questions…

If it is a high resistence in the wire then I can replace it

but

If the swapped relay solves the problem

Can I SERVICE the relay by pulling it apart?
OR
do I need a new relay?

Any comments?

Bob(Brisbane,Australia)

[ted280sl]

Bob,
  It sounds as if you would like for your car to start right up when you turn the ignition. I had my cold start valve rebuilt and I replaced the relay without much impact. I was told by Ray at SL Classics to try changing the coil. He explained to me that the 190SL and most 113's came with a weaker coil. He suggested that I upgrade to the "red coil" with the associated red ballast. I did that and the car starts much better.
  I hope this information is useful.
Regards,
Ted
1969 280SL with the Red Coil

[bayleif]

Bob,
It sounds to me like you may have high resistence in the time switch. It's operating, but not working. If that makes any sense.
Chuck
Red 280SL

Chuck Bartlett
1969 Signal Red 4 Speed

[Cees Klumper]

Bob, FYI: a new time relay lists for about $110 here

[George Davis]

Bob,
not meaning to be flip, but after you finessed the visor mirror, I'm convinced that if anyone can service the relay, it's you.  If it is the problem, there's nothing to lose by trying it. I'd guess there is just a simple set of contacts in there that need to be cleaned up.

Good luck, and please let us know how things turn out.

George Davis
'69 280 SL Euro manual

[hands_aus]

Hey Guys,

Thanks for your replies,

As you know I have been investigating my cold start problem.

Ted,
the car starts very easily when hot, the coil and points etc are fine , however when it is cold it starts very easily ONLY when I use the by-pass switch to give the CS Valve a short burst, if not it just takes forever to crank to life.

George,
The relays proved to be working properly. I wired up 2 test lamps to the relay, one on each contact, and then operated the relay. Both test lamps were equally bright but no voltage at the CS Valve.

I swapped the relays and no action from the CS Valve.

I reinstalled the original relay and full power to the CS Valve.

Chuck,
It turns out to be a “nearly broken” wire in the harness that is causing the high resistance and hence low voltage to the CS Valve.

When I jiggle the wires around the fault occurs intermittently.

This also was the reason the second relay didn’t send power to the CS Valve.

That “nearly broken” wire will be repaired tomorrow. I have reservations about cutting into the harness braiding. Firstly I will make sure it is not in the connection of the relay plug.

I moved the wires until I had full voltage at the CS Valve then I started the car and went for a short drive to the local German wrecker and bought

6 spark plug tops
4 relay rubber mounts plus threaded screws/washers etc
2 relays, 4 pole, normally open contacts….. just like the starter relays
1 flasher relay
1 relay with 2-3 second delay before operating, normally open contacts ( I would have been delighted if it was normally closed because I could make a small time switch to operate the CS Valve every time).
1 silver looking canister about relay size that looks like a condenser (I am not sure about this item, it might work… it might not)
All these items WORKED and were from a 300 SEL and cost the princely sum of $20.00.. I thought it was a good deal.

I now have some spare relays BUT that shiny canister has me interested.

Bob(Brisbane,Australia)