Low Inlet pressure, make up gas and EPC are fine

Hello and Help!

   My GC-FID's inlet pressure stays at 0.7 psi and does not reach the setpoint of 10 psi. Makeup gas reaches the 25 psi setting. Liner and septa are fine. I unscrewed the inlet column nut and placed my finger at the bottom of the inlet, gas flow stays at 0.7 psi when I plugged the inlet with my finger but when I let go I have no flow anymore. I changed the EPC with another, from a different instrument but same part number, and is showing the same results so I switched them back. I'm using methanol to find a leak in the weldment but I don't see any bubbles either. I haven't changed the weldment yet but it might well may be the last thing for me to try. This all started when I changed the carrier gas from Helium to Nitrogen as I can't be supplied Helium anymore. I ran a first vial with a steady Nitrogen flow, no problem, but as I was running the second vial the instrument stopped halfway through the run and the flow issue arose ever since. I'm running out of options and hope you have seen anything like this before or have a suggestion I might try. I will greatly appreciate your time.



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