could you clarify a couple of things * the added 'port' in question.....was this a peice of piping smaller than 3/8 inch prior to the metering device that you removed * unless i misunderstand, i'm assuming you were concerned it was creating an extra restriction.
you didn't mention filter/drier or vacuum gage. you clearly have a starved evap, possibly due to a restriction. obviously if you charge until the sh is in an acceptable range (5 to 20 nominal), the discharge pressure would probably be out of sight. the following checklist includes some standard refrigeration items for your consideration. rule out variables and you will pinpoint the problem. there are only two possible restriction points, but make sure all other conditions are correct.
- verify no leaks. a vacuum pump will pull in air/water through a leak.
- change filter/drier whenever system is opened to the atmosphere. if it is restricted even a little bit, the added restriction will cause the sp to drop and dp to rise. the evaporator will starve and the sh will rise.
-always use a vacuum gauge when pulling a vacuum. air is one of the non-condensables, water is the other. a proper vacuum will boil water, but without a vacuum gauge, you do not know if you still have water.
-verify clean condenser, evaporator and filter. verify matched evap and cu. verify correct ducts. verify no ra leaks. correct readings depend upon normal conditions and correct design.
-verify good run capacitor. extended running time with high dp and high sh is probably causing the ol, but do the checks. there are several ways you can verify the capacitor. you can use an upper end digital meter or analog meter, you can verify mfd against rating, you can do a running capacitor test (let me know if you need a formula). first, though, check the compressor amps against rla rating.
sounds like the problem may be a restricted liquid line filter drier. measure the temp of the liquid line entering and leaving e filter/drier. if you see any difference, you have an added restriction causing low sp / starved evap / high sh. for the same reason, the dp goes up. the compressor pumps at a constant rate. the normal restriction by design at the md causes the differential between the low and high sides. extra restriction causes that differential to be exagerated, resulting in reduced saturation (liquid/vapor combination) in the evaporator as well as backed up liquid driving the dp up. if the filter/drier is not restricted, call carrier and verify the piston is the correct size. if it is, the other possible culprits include system design (evap mismatch) and non-condensables (water and/or air).
let us know what you find out.