won't start after w/p replacement
 

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

I remember doing 2 waterpumps on mid 70's SL's and dont remember taking out the distributor, did you turn the engine while the distributor was out ? if you did you might be 180 degrees from TDC, to find TDC remove all spark plugs, find the #1 Cylinder, it will be the most forward cylinder, turn the engine in the operating direction with a socket on the harmonic balance while plugging the spark plug with your finger, when you feel the air pressure pushing out that is the compression stroke and stop and look at the timing marks and line up to 0, replace the distributor with the rotor pointing to the #1 cylinder on the distributor cap and make sure the firing order is correct and that should get you timed and able to start,

Post your findings and results

I agree.