A 73 450sl is an r107, and the correct forum for that car is here: R/C107 SL/SLC Class - Benzworld.org - Mercedes-Benz Discussion Forum
Perhaps a moderator could move this thread over there, or you could start a new thread.
Good job at least narrowing down whether your problem is with spark, air, or fuel.
There is no carb on a a 73 450sl (or any 450sl). The 72-75 are D-Jetronic Bosch fuel injection. There are a few things it could be, but the most common is the fuel pump not running, which could be the fuel pump itself, or the fuel pump relay (often abbreviated FPR since it is such a common problem on all 107s, D-Jet or not).
The good thing about the fuel pump relay on the D-jet 107s is that all the relays are the same, and you can simply swap out the FPR with another relay, and usually see if that is your problem without spending a penny.
The bad thing is that you will have to:
- remove the fuse panel cover in the passenger footwell
- remove the chrome strip at the front of the door jamb.
- remove the cardboard side panel
- remove at least one screw to get the metal bracket out of the way
- pull out the FPR, which I think is the top front (or left as you are looking at it) relay, and put another in its place.
The w107 group is incredibly helpful, and taught me everything I know. The FPR was a problem I had early on in my 73 450sl ownership. It is quite common, and the forum quickly helped me out. The forum has an "encyclopedia" for all of the tips and trick to owning these cars, and you definitely should read it, or at least understand the information that is there if you are even considering 107 ownership.
- That should lead you to here: http://www.benzworld.org/forums/r-c1...ml#post4819292
I hope to see you in the 107 forum.