1973 MB 450SL Throttle Switch- Should Injectors Fire?

Hi Kevin,

inches for me is a length measurement, not a pressure unit...

But if MAP sensor is not leaking vacuum then a bad engine vacuum has nothing to do with D-Jetronic. In such cases there are 2 things to do. Insert smoke to test whether it evaporates somewhere. And use a pressure loss detector to verify that piston rings and valves are tight.

Thank you again for the response. Does anyone on the forum have access to a vacuum diagram for a 1973 Mercedes 450 SL? At the very least, I am interested disconnecting/plugging all vacuum lines not essential to running the engine (i.e. is central door locking, HVAC, etc.) I have the benefit of one dodgy diagram that I will attach. In the diagram to the immediate right of number three appears to be a singular connection to the manifold, presumably the origin of the vacuum for a number of features.Basically, I would like to remove the area between the firewall and the license plate from the equation.

Hi Kevin,

check 107 SL Workshop manual above to verify heating, air condition and central locking chapters. They all contain vacuum diagrams.

1025MB wrote: ... As I turn the crank/distributor, each of the four triggerpoints appears to stay closed for roughly 100 to 110°....

Hi Kevin,
the triggerpoints are misadjusted.
They have to stay closed <and open, too> by around [strike]180°.[/strike] 140°

Unfortunately there exists a youtube-video showing the adjustment to 110°.

Use my tool and you can adjust them correctly without using any angle measurement.
trigger-tool-thread

Regards
Norbert

Hi Norbert,

sorry to correct. but 180° dwell for trigger points is too much as well as 110° is too little. When I replace cams and adjustthem with 0,5mm gap with my alignment gauge, I see 140-150° of dwell on my ignition distributor. 110° dwell means that T.C. are not in mid and will over time come to 140°.

However, it will not be Kevin's problem. Dwell is not an important issue on T.C. as long as it is not too far away.

Hi Volker,
Kevin didn't write anything about a 'dwell'.
He wrote about the closing angle.

This is exactly what the youtube guy does: He measures the angle using an angle-meter-disk.

Look at the reading of your oscilloscope: opening time and closing time of the points are same lenght or almost the same lenght - how can the angle differ than?

A closing angle of 140° would mean an opening angle of 220°, and the oscilloscope readings wouldn't look almost same lenght.

Which way do you measure the dwell?

Regards
Norbert