Outer Limits 4x4 Board

Put a clutch booster on my dx patrol ( no booster from factory ) plumbed it up with a check valve and lines from a doner patrol .But now the clutch pedal wont returne once depressed with engine running . driving around at the moment with the vacuum blocked off - freeplay and bleeding all ok.
not sure what engine the booster came from , vacuum measures 26 inces of mercury I know a petrol one will only run at 18 or so. wonder if it needs a return spring on pedal ?? anyone done this conversion B4 ?? thanks Christo.

check the hose going to the slave cylinder !