I AM FINALLY GETTING AROUND TO FIXING MY '73 280 SEL 4.5 IT HAS BEEN IN THE BARN FOR OVER A YEAR NOW. IT HAS A FUEL INJECTION PROBLEM. THE LAST OWNER COULD NOT FIX IT AND WOULDN'T PAY TO HAVE IT FIXED. THE CAR WILL RUN BUT ONLY WITH A WIRE RUNNING TO THE THE FUEL PUMP FROM THE BATTERY. WHEN THE CAR DOES RUN, IT SOMETIMES ACTS LIKE IT IS STARVING FOR FUEL. I SUSPECT A TIRED FUEL PUMP AND FAULTY RELAY. I HAVE PURCHASED A NEW FUEL PUMP. I HAVE A PARTS CAR FOR THIS ONE, A COMPLETE '72 280 SEL 4.5. I WOULD PULL THE FUEL PUMP RELAY OFF THAT CAR TO FIX THIS ONE IF I KNEW WHICH RELAY IT ACTUALLY WAS. I GUESS I COULD HAVE TAKEN THE FUEL PUMP ALSO, BUT I WANTED TO NOT HAVE TO DO THIS AGAIN IN MY LIFETIME. IS THERE A PLACE IN THE CD MANUAL WHERE IT GIVES THE LOCATIONS OF THE PARTS, IF SO WHERE IS IT LISTED? ANY HELP WOULD BE APPRECIATED. THANK YOU.

The fuel pump relay and the fuel injection controller power relay are behind the passenger side headlight. Same place as the EFI controller. There are 4 relays and the two mentioned above are the square/rectangular ones. The cylindrical ones are the separation relay (has to do with timing) and the aux fan (I think).

The square/rect relays can be IDed by looking at the positive battery cable. The smaller power wire attached goes to the EFI controller relay and that means the remaining one is the FP relay. The FP and the EFI relays are interchangable with each other.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician