Losing air when filling Marauder

Are you using a hand pump or bottle? I have the same trouble filling from my Air Venturi 4500 bottle with the reg set at 2900. My compressor fills the bottle to about 4700. Hook the bottle to the rifle and fill to 2900. The bleed valve does not bleed real quick like my pump does. It ends up around 2700. After bleeding and before I disconnect the hose, I fill to 2900 again. This time it stays at 2900 after bleeding. This is a good example of a bad fill valve in the rifle. If I am just shooting targets, this is fine. But if I am going hunting, I finish filling to 3200 with the pump. I do not loose any air while bleeding off the hand pump no matter what fill pressure I stop at. The pumps valve releases the air like right now. No pisssssh. Just a quick whoosh. I thought it was a bad fill port on the Marauder too. So I changed it, I even put a whole new tube end with new fill port also. No difference. I believe my trouble is the AV reg. The stupid (poor design) bleed valve knob is kind of hard to open fast. I am going to cross drill it and turn it into a T handle. I also have a hard time closing the valve tight enough. Lots of times I hear it hissing/loosing air as I fill the rifle. Have to crank it down tighter. Please let us know what you find. 
 
I've been out of town, in that thriving metropolis of Minneapolis, MN. Nice place, but home is good!

I'll probably spend some time looking at this over the weekend. It seems to be a new problem for me as the valve worked in the past and I lost very little air, which is why I was concerned. may also call Crosman customer support and ask if this is normal. Losing 200PSI at the beginning of a shoot is a real blow to your shooting if you know what I mean.

 
Just had a conversation with Crosman Support. They were Fast and Friendly!

Said, open the bleeder valve FAST and let the one way valve slam home. This may cure itself after 3 or 4 fills using the technique.

If this doesn't work, put a couple drops Crosman Silocone Chamber Oil directly into the fill nipple so it can get into the valve. Do NOT use any normal gun oils as they will eat the seals (and I thought dieseling was the big deal!)

While dieseling will damage the gun, the normal oils will eat the seals completing the damage.

I believe I've got some silicone oil at home. If not, it's a trip to Wally World as I believe they keep it on the shelf.

I'll let you know what happens!
 
Try the silicone oil a couple times. It only took twice for mine to loosen up and start working right again, your results may vary. 

​Talked to my son, he used to airsoft quite a bit. He said there were similar problems on some airsoft equipment, and lube was always required. I also remember an American Airgunner where they were talking about C02 guns always needing a drop of silicone oil on the top of the C02 cartridge before inserting. The oil kept all parts and seals lubricated and extended life. He said he liked to pick up old beaters at flea markets that wouldn't hold air. After a couple drops of oil, good as new.

​Gun is over 3 years old, though not nearly as much shooting as I'd like to have done. Life got in the way.

Good luck!
 
I could not figure out what was going on with my marauder pistol. I would fill my gun and as soon as I would bleed it, all the air would rush out, "whoosh!!".. I looked and looked and couldn't find anything on it. So glad I ran into your post. I did what was suggested. Put a few drops of Super Lube on/in the foster fitting. And after a couple rounds of filling and bleeding it fixed the problem. Really appreciate it.