OKAY.. My Uncle bought the '72 280SE 4.5L not running...
1.) Replaced the Bosch fuel pump with an airtex (I know prob not best but works just fine as far as pressure etc..)
-- this thing would only run after trying to start with injectors plugged in which led me to believe that the fuel injectors were opening at the wrong time and the engine was just burning the fuel the injectors dumped into the cylinders..
2.) After several possible causes and reviewing the best info by far (http://w107.pbworks.com/f/DJetronic.pdf
) I concluded the thing needed a new or used ECU.. REPLACED THE ECU AND THIS BAD BOY FIRED RIGHT UP!!
3.) Replacement of the ECU got the car running but NOW HERE'S THE PROBLEM...
----The car seems to run okay at cold start with MAYBE a slight miss (or just a minute stumble every so often) when the vehicle warms up a bit it runs rough and stalls a lot.
I unplugged the Air Temp Sensor from intake bellow and it seemed to run better but would still have an RPM drop (or that slight miss/stumble in idle or even accelerating down the highway).
3.) Now I have replaced the intake air temp sensor and to my dismay; the vehicle is running rougher than before with almost a dead miss while idling and idling a lot lower (sounds like this thing is loping from a cam) and it is bogging down and missing when under load where as before with sensor unplugged was running ten times better. (have not tried to run with sensor unplugged again..)
4.) Now we did adjust valve clearance a bit (to the ones on the passenger side because I had room to utilize my spring compressor tool and loosen the ball adjustments with a deep socket) ALSO AS A NOTE THAT WE ACTUALLY DID THE VALVE ADJUSTMENT AND REPLACED ALL EXHAUST HEADER GASKETS IN STEP THREE BEFORE REPLACING THAT SENSOR. (however I do not think that us removing the valve covers and adjusting the valves hurt the vehicle since I am pretty darn sure we didn't over or under adjust..
5.) Now I am running out of ideas... I thinking I will double check fuel (even though this was holding at 28ish while running and the accumulator and regulator for fuel are operating normally) ALTHOUGH IF ANYONE HAS A GOOD LINK TO CHECKING THOSE AGAIN WOULD BE APPRECIATIVE!
ALSO: another note is that we did replace all the rubber tubes above intake and while having the cold start and Aux. Air Valve off of vehicle we tested them.. (THE AUX AIR VALVE DID NOT CLOSE UNTIL I STUCK A BLOW TORCH ON THAT THING THOUGH!!!)
MPC, air temp, engine temp, and coolant temp all seem to ohm out just fine in accordance with the specs in the D-Jetronic troubleshooting and with what others have said.. I am stumped guys!!