I have a 94 Z71 w/ drum rear and disk front, all new pluming and shoes/pads. I've can get the brakes to pump up fine with the truck off but the moment I turn it on the brake go to the floor. Everything has been bleed a bunch of times what more do I need to do? Do I need to charge the abs valves?

That sounds like a bad booster.

Is there a way to test the booster?
Thank you

Basically what you describe is testing the booster and I agree with Ruffneck that it it bad. Do you hear hissing (Vacuum escaping) when the truck is running and you press the brakes?

Kind of, its not an actual hissing, I’ll listen again tonight.
I thought if the pedal stayed harder than normal after you turn the truck on, that meant the boosted was bad.
I’m not sure if this will help but the sound is coming from the m/c. I found out the hard way that you can NOT bleed the brakes with the m/c cover off, Brake fluid go’s everywhere. When you do pump the brakes with the truck running and then take the cover off the fluid is always milky with air.

Again thank you for the reply's.

It depends where it is leaking. If you are hearing a hissing sound when you pump it the booster has a leak.

Well last night I had another listen and honestly it doesn’t sound like a vac leak, but it may be. It looks like the sound I’m hearing is the brake fluid being pushed back into the m/c reservoir.
I’ve only had this truck for a short time. When I first brought it home the brake were soft but seemed to work fine.( In hind sight I may have only had rear. I’ve only drove the truck under 20mi since I’ve had it) I could hear metal on metal so I changer the front pads. After the change I took it out for a test drive and a few miles from home I blew the f/r brake line. I got the truck home but drained the m/c trying to get it back. I put on a new line and filled the fluid and took it for another ride, blew the f/l line this time. Replaced this line and wouldn’t you know it I blew the rear lines.
O.k. now I have all new lines, front calipers and brake pads/ shoes. I’ve gravity, vacuum, and regular bled the system multiple times. As stated above I can get pedal fine with the truck off but the moment I turn it on it goes right to the floor. The truck will stop but the pedal is on the floor and there is no way that this is correct. Al so if you give the brakes quick short pumps it will build up a small amount of pressure that will last one stop only.
I hope this helps the Doctors diagnose the problem. Any the all help is greatly appreciated!

Any help?

Rear Disc conversion completed on 93 Z71
 

I started this thread, when i was having problems getting air out of my system. I finally found it. I had purchased the wrong fitting, which was not sealing off and was drawing air in with the fluid. (My Bad). Anyway i have pics of the conversion. I also totally eliminated the ABS garb. Some may like it and some may need it. I so far have never needed it in my 37 years of driving. If you use common sense when it is wet or ice, snow. Then you can drive safely without ABS. I used a lot of ideas from guys here and other places to help with this project. I have the best brakes that i have ever had on this truck in 12 years. ABS can create a multitude of problems. This is one reason i eliminated it. The company i used for the disc brake conversion was KingTec. Not a very informative company. I could tell that they were more into just selling the kits. Anyway i put the disc on the upper front of axle first, but found out that i had to remove the calipers to bleed them. So i rotated the mount and put them on the bottom rear of the axle. This way the bleeder was pointing (up). This lets the air out easier. Hope i load these pics correctly. Thanks to all for your help in this conversion and the air bleeding problem i had,(which was my fault with the wrong fitting). This is a great site for info.

Anyone heard of these brake pads?