2 way valve operation.

[Ron.K]

I have a 1970 280sl with the emission system. At the PUB last year, Dan Caron noticed that my 2-way valve was not working when the engine rpm was increased over 2400rpm. It was not getting 12 volts. He suggested to send both the speed relay and relay box in for repair, which I did. Turns out the speed relay was defective and the relay box was good. They repaired it and last weekend I installed both. I still do not get 12 volts at the 2 way valve when I increase the rpm. I looked at the wiring diagram on the emission page and noticed that the transistorized relay box under the battery is also in the circuit. Last summer I also installed the 123 ignition system into the car which does not require the box under the battery, so I bypassed it. Does anyone know how to now wire this 2-way valve circuit with the transistorized box not in the circuit?

[Ron.K]

Well, last night I reviewed the wiring diagrams for the emission system so I fully understand how things operate. Tonight I had a plan on how to troubleshoot this. I checked for incoming power to the relays, which was fine. I checked the 17 deg switch wiring and the 100deg switch wiring, all checked out ok. I started the car, pulled the wire off the 100 deg switch, put a jumper on the wire to ground and the 2 way valve clicked open and the motor RPM increased, because it advanced the distributor, perfect... I tried the same thing on the 17 deg switch and it worked as well. Great. So now I increased the RPM over 2400, but the 2 way valve does not open. Can anyone tell me how the speed relay detects the rpm?

[jeffc280sl]

check the forum under my name.  Also check the tech manual.  I did a complete write up a few years ago.

[Benz Dr.]

Ron,
you really want this to work or you will loose 20 - 22 degrees of advance.