ok folks, heres the scoop.
The jeep combo valve is a GM part. I was thinking early Chrysler, forgetting about AMC. Its a common one, just the procedure is a little bit different.
The problem with the OP's jeep (any many others from the sound of things) is that any air trapped in the combo valve will result in a failure to bleed the lines. The valve will off center, making the bleeding process ineffective. The valve must be re centered and held in its center position. this tool will be screwed in where the idiot light sensor goes and will hold the tiny valve for you.
This valve makes the test with the pinch off pliers inconclusive. It was however a fantastic thought, but the valve that has the capability of moving without your input, therefore making any blockage of the lines in the name of testing inaccurate.
I think this is the one you are after, however I would double check your measurements.
http://www.summitracing.com/parts/c...W1nV6uFIxQjEWEhZmomOciNEsYuFOCsDGIaAmTG8P8HAQ
Next, I would advise the combo valve be disassembled and cleaned out with brake cleaner, and thoroughly inspected with a magnifying glass. Any deep scoring, broken springs, or cuts in seals means its junk.
I would be willing to bet this tool can be acquired at the parts house, I will check and get back to you guys.