purge valve question

I have been chasing a p0455 check engine code a large evap leak. I just got a vacuum pump gauge and I added vacuum and it isnt holding. That mean the valve is no good right? Shouldnt it stay at like 9?

Never dealt with it but I'm wondering if you can disconnect the vacuum lines at the valve and plug them to take the valve out of the system then try your leak test. Here's a video that shows how a shop t-shoots EVAP leaks on an 02 Caravan.
http://www.youtube.com/watch?v=CSn0ljUS6kI

Don't recall if it's pressure or vacuum but I've read applying too much of one or the other can damage EVAP components.

Never dealt with it but I'm wondering if you can disconnect the vacuum lines at the valve and plug them to take the valve out of the system then try your leak test. Here's a video that shows how a shop t-shoots EVAP leaks on an 02 Caravan.
http://www.youtube.com/watch?v=CSn0ljUS6kI

Don't recall if it's pressure or vacuum but I've read applying too much of one or the other can damage EVAP components.

I took it physically out of the van and put it on the bench and connected my vacuum gauge. squeezed till 15 lbs and it just leaked out. I checked my connections so I'm sure it is the purge valve leaking. I tried both ended of the valve. I didnt check the solnod though What I have read the intake side of the valve should hold like 9 lbs and then when you apply voltage the vacuum is released.

I discovered 3 - error codes P0442, P0443 & P0455 after taking my 03' Suburban to get smoged. Went to my mechanic who did a smoke test found leaks on both (cracked vent/rollover valves) from the top of the fuel tank. Fuel tank replaced, $1,100 dollars later code P0455 came back after a week or two . Back to mechanic discovered bad contact where the wires connect to the molex connector to the canister purge control solenoid while moving wires around because it would work then not work. He ordered the connector, I replaced it myself. Took it back so he could clear the code. Code back (P0455) after a week or two. I replaced the gas cap with an OEM. Took it to my friend who read and cleared the code. Code was back after a couple weeks. Where do I look next? Please help I'm going crazy. I really need a DIY fix cause I'm running out of cash....