vacuuming a/c - what am i doing wrong?

i have a robinaire spx 6 cfm vac pump... filled it up with vac pump oil and busted out the manifold gauges.. connected low side to low, hi side to high, ... pulled a 3 hour vac and couldn't get the gauge to go any lower than -30 microns... so i charged the system up and with only 1 can of r134a the low side pressure shot up to 60 psi... i know something had to be wrong, so i went and got my other gauge and sure enuff it still showed 60 psi on the low side... i immediately shut the car off and as i type im running another vac on it... i have no clue what i am doing wrong.. this is the first time i've ever evacuated a system and recharged it before and im starting to think its going to be my last... any help is greatly apprecaited.. thanks

correction i could only get a -20 micron vac on it! anyway i ran another vac on it this time for about 30 min... then i went ahead and charged it.. this time it took 3 8oz cans of refrigerant and 1 11oz can of oil... after about 45 mins of it being on it shut off... i think its the high pressure side shutting it off since the low pressure side is at about 55 psi... any way im thinking after the oil gets in their enuff its going to lower the pressure... hopefully it doesn't take long enuff as i don't have a/c for much longer...

doesn't the high pressure side stay lower during the heat of the day? im thinking thats going to protect me from the heat :)

anyway i shall see if anybody has an recommendations go right ahead.. thanks all

High side pressures generally increase as ambient temperature increases, and as latent heat increases. Reconnect your gauges and subcool the condenser (running water) and you'll see the effects of a colder condenser.

11 ounces of oil? Was that a full 11 oz. or one of those pre-charged cans with about 2 oz. of oil in it?

it was a full 11 oz can of compressed oil that i got at autozone... i think my problem is my vac its not sucking like it should.. im going to get another fitting for it and run another vac hopefully this time i can get it to -30 and hold it there...

also... when i run a vacuum on it... should i refill it with oil? if so how much? is 11oz way to much? the manual said 9oz to fill the compressor.. any help is greatly appreciated

**at least now it holds pressure with the new compressor :)**

You could have a leak in the system, or you may be removing the freon from the oil in the system. Oil can hold freon. Pull a vacume on it for 20 min. Shut your guages off. Let stand for 20 min. If the guage reads 0 then you have a leak. If it only goes up a little your good to go. PULL A VACUME FOR 20 AND LET SIT FOR 20. DO THIS 3 TIMES!! Then charge the system. Then you should be good to go.