Were you able to get a reading on the voltage to the start valve when it didn't want to start?

Maybe the valve itself is flakey?

BTW - my friend Jim Freeh, who bought my 300E last summer, is having this exact problem, and he has not been able to figure it out either. He has an "extra" 300E and he has swapped all the components in the loop withouth success in isolating the problem.

__________________
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