Help! My '75 450SL won't start. I installed a new waterpump. I was careful to R&R the distributor at TDC and marking the rotor to distrib housing.Pretty sure all vacuum hoses hooked up properly. Only thing on the Power steering pump there is a peculiar switch with a lead that runs down to crank shaft pulley-looks like a sensor and another lead with a cirular plastic end with a hole in the middle. The switch itself on the p/s steering pump has a screw on cap. Any idea what it is? I plam to ck timing. Anything obvious that I'm missing? Thanks, Mike