1983 280 SL starting issues

[zakkkk]

After sitting in the garage for 2 weeks the M110 engine always was a bit tricky to start from cold. It seems like the fuel was leaking back to the gas tank when sitting a while.
I learned the trick of turning the ignition key back a notch then forward again to allow the fuel pump to pump another bit of fuel to the engine before cranking . You actually hear the pump pumping for a second.
I would back off with the key 4 or 5 times and the engine always started- shaky at first then rock solid after 5 -10 seconds. Never any smoke. This was fine.
Last weekend I went to start the car and did the ignition key trick but it was different this time.
It took me 10 trys to start the engine this time.
Each time I did the key trick for now 6 - 8 times each the engine would start and run for maybe 15 seconds then die. It seemed like then engine was running on the fuel from the key trick only then die.
It does not seem to be an electrical problem.


I would like to remedy this.
So what should I be looking for?
- bad fuel pump?
- leaky fuel lines?
-clogged fuel filter/ fuel lines?
- all of the above?


Another clue is that if I drive the can on consecutive days the car starts right up even without the key trick. And once the car is running it is perfect. Hot starts take a quarter turn.


any advise would be appreciated.


jz

[rocky raccoon]

If the 280 has a fuel accumulator as do the 380/560, then that is probably your problem. The accumulator maintains fuel pressure during periods of inactivity, certainly overnight or longer. On the 380/560 it is located in the fuel cluster just forward of the right rear wheel.

[Frank Reiner]

There is an accumulator, and a leaky diaphragm in the accumulator is a high probability.
A second place to look is in the fuel pressure regulator which is installed in the fuel distributor. There is a check valve within the regulator that holds pressure when the engine is shut off. The o-rings of the regulator and the check valve do leak eventually.
A third suspect is the check valve of the fuel pump.

[zakkkk]

Thank you gents for the replies and insight.
I will follow up.


jz