What's the reading suppose to be on the low and high on the manifold gauge when the pump is running? What should it be when its off? I'm getting zero on both side. Is this normal? If there is a leak in the system what would it read? I have a 94 EX with R134 system.

 

Zero pressure means you have no refrigerant, almost certainly due to a major leak. The compressor should not engage in this condition, as there is a low pressure cutout switch to protect the compressor. Normally with the compressor off (and it has been off for a long time, a so-called "static" situation) both pressures should be around 90 psi, more or less depending on the temperature.