Close the high side valve and charge into the low side. It should just suck it right in if you are charging with the enigne running.

A lot of new machines are set up to charge into the high side but as you have found out, that is not always the best way. Ideally you pull a vacuum and that vacuum will pull in all of the required refrigerant. Charging into the high side is ok if that works out. If it doesn't then compressor operation just tries to push it back into the machine which sounds like what you are experiencing. So just charge it into the low side. Even if the machine is set up to charge the high side it will do if from the low side.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff