Hello. I am using a 7890B GC system. I recently found that if I connect the gas sample line to a gas resource, I can only detect very small flow rate in the gas sample vent, even I had over 20 PSI inlet gas pressure. If I increase the gas inlet pressure to 50, the flow rate out of the sample vent will be a little bit higher than 20 PSI but still very low. It doesn't look a leaking issue, because even though I turn V8 on run bypass, the vent flow rate is still very low. It looks like the resistence through the system or V8 is very high. I've checked the V8 alignment, it looks ok. I am wandering what other could cause this problem. Thank you.
I have updated your tags for visibility. Can you provide more detail on the GC? Is this a single valve system?