TDC Indicator??
 

I spent all day trying to figure out what this is and used for. 1975 450SL

My driver has this sitting there with 2 whitish leads running from this, and a 3rd with 2 wires going to the wire block under the resistors on the drivers wheel well. One of the leads goes to a black cylinder with a hole thru it, the other was unknown, it has a screw cap with a electrical receptacle under it.

The bracket that hold this mounts to the power steering pump.

After looking at the one on my parts car I see 1 lead goes down and is mounted to a bracket by the crank timing pulley, so mine was broken there.

what is it used for and is it needed?

I have a few pics but do not know how to add them here. I do not see a manage attachments button

ta dah
 

the top is the one that goes to the bracket at crank,
the bottom has the hole thru it,
the left lead in the 2nd pic has the 2 wires for the wire block,

That's the closest thng there is to a dignostic port on a '75 D-Jet. There is a Hall-effect sensor that is aimed at the harmonic balancer, looking for a nub that is aimed at the sensor when the engine is at TDC. The only use is for a timing meter. The little 'shoe' on the fender that looks like a wire connector is the terminal for an external tachometer for use while setting the idle RPM.

Mine was missing when I got the car, and it really isn't needed. If I could figure out how to get a 36-1 tooth wheel on the balancer, it would be perfect for the Megasquirt project to use the sensor bracket.

Scott

Thanks for the info, I have 2, one with a broken sensor housing

I removed and still seem to have issues with the EGR removal and vacuum lines, backfires when I rev. So I just wanted to make sure that was not the problem.

I added the Crane kit hoping that would help but no.

If I remember correctly, Backfiring after revving the engine is usually a timing problem, but it's been decades since I was involved in that vehicle.

What are you having trouble with on the EGR removel? Do you have a digrm of the vacuum lines? There is an online vsite with the Service manual here: Model 107

Searching through that will give you a LOT of info.

Scott

when i replaced the E manifolds I lost EGR mount and am trying to figure out what vacuum lines and if I still need the vacuum switch as it T's with the dizzy advance line.
why electric on vacuum pods?
I am also trying to find out if I need to change the timing and what other adjustments are needed now that the cats are removed.

I'm planning on using the valve mount on the left manifold to put in a wideband O2 sensor, so I have to figure out the same thing. The Electric Thingys (sorry-technical term :-) ) are electrically operated valves: If a sensor, such as a temperature sensor, is warm enough, then it will send a signal to the valve, letting it open or close to permit or prevent vacuum to go to a device, such as the vacuum advance/retard.

Scott

I set timing to the 1974 (no cats) spec of 5 ATDC and it ran great, however when I came home I was going to check the varying degrees of timing at the different RPM's I noticed the timing at 750 RPM's went to 12 ATDC.
Does timing need to be done with hot or cold engine?

I do not know if I want to mess with because it has never ran better... SO FAR!

I'm mot too sure I'd mess with it if it was running good. If it can pass emissions, or a reasonable facsimile thereof, just enjoy the ride.