No problem to start the car with 7 and 8 jumped - that's the connection that the relay supplies when it's working. Not a good idea to drive it that way, except in and emergency.

There are any number of things that can cause a 380 not to start, but the ECU is down the list. It's function is to make minor tweaks to the mixture when the car is running. It's also quite rare for one of them to fail.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe