Your new regulator could be bad (unlikely).

The fuel pump could be going crazy (unlikely).

I don't have my 300E anymore, but I would think that you would unhook the fuel return line at the tank, stick the end in a suitable container, run the pump for 10 seconds by bridging the fuel pump relay, and see what comes out. If mechanic 4 can't do this, time for mechanic 5.

Suggest not smoking during test.

__________________
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