I'm subscribing to this thread because I have a 77 280SL in with start/running issues. When first brought in I sprayed a little starting fluid in air cleaner and it started up and idled out well until getting up to temp then shut down. It would bog down if given throttle during this time. Next I pinched off return line at tank and it started and would rev during throttle application. Then the return line split and started leaking. I've got a new filter/pump coming and will do smoke test on system over next few days. Will replace hoses as necessary. I've still got more troubleshooting to do.

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Jim