ON THE THE 85 300 TURBO DIESEL ENGINE YOU WILL FIND A "PRESSURE" LINE FROM THE COMPRESSOR HOUSING TO THE WASTEGATE,IT TRANSMITS BOOST PRESSURE TO WASTEGATE.
ON 84 AND 85 TURBOS THERE IS A VACUUM LINE TO THE BYPASS VALVE ON THE COMPRESSOR HOUSING,THIS BYPASS ALLOWS THE COMPRESSOR SPIN-UP WITH OUT CREATING BOOST IN THE MANIFOLD DURING E.G.R. "ON" PERIODS.
THE WASTEGATE AND FUEL CUT-OFF WERE ONLY INSTALLED AS PROTECTIVE DEVICES AGAINST COMPRESSOR SURGE (A VERY DESTRUCTIVE EVENT THAT OCCURES WHEN THE TURBO HAS RUN-AWAY BOOST)
WHEN THIS ENGINE AND TURBO COMBINATION WERE SELECTED CAEFUL CONSIDERATION WAS GIVEN TO PREVENT SURGE EVEN WITHOUT THE WASTEGATE AND FUEL CUTOFF.
MF