560SEL cranks, starts sometimes
 

I have a '91 560SEL that will crank but seems to have a fuel problem. When I pour fuel in the throttle body (TBI) air section, car starts everytime and runs until fuel is gone. Fuel press at TBI is initially 70psi then steady 35psi. I loosened injector lines and cranked car, but no fuel seems to be getting to injectors. I removed the "round" section at rear of TBI to check the pushrod for movement. I seems to be working fine. Can't seem to get power at the 2 pin plug on driver's side of TBI or the 3 pin plug on passenger's side of TBI. When I push the round plate down in the air section of TBI, the plate stays down. Is this normal? Even so, car starts and runs when gas is poured into the air section of TBI.

I have fuel present at the inlet line, the outlet line and one little line that goes to what appears to be a round, vacuum operated pressure regulator. There is no fuel pressure at any of the injector lines.

If anyone could help, I would appreciate it. Thank you.

Take the input fuel line off of your fuel distributor and check the valume of fuel comming with ignition key on in position 2. You should get around quart or 1/2 liter in 30 seconds. Do you have mechanical or electronic injectors (only fuel line connected to them or wires too)? I believe my old 1980 280SE is same 126 body and same fuel distributor system as yours, injectors need about 55psi to operate. Inside the inlet fuel line connection, there is a fine mash screen, check if it is clean. From your description, I believe your fuel pump relay is not turning on or staying on.