Date registered: Feb 2010
Vehicle: 1972 280SEL daily driver. 904 Dark Blue with cognac interior. euro 4.5 engine
Location: Williamsburg, VA
Mentioned: 3 Post(s)
Quoted: 34 Post(s)
According to the wiring diagram for the 4.5, there are only 4 contacts into the fuel pump relay so the 4 pin should be fine. My guess is that this is a multi purpose relay so there may be some normally closed contacts that open with the relay being energized. Not necessary for the fuel pump.
Pins 85 and 86 should be power to the coil in the relay and pins 30 and 87 go to the contacts in the relay.