No pedal while running.

[Pappy G]

About 6 months ago I replaced booster, master cylinder, calipers, brake cylinders, hubs rotors. Had good pedal and good brakes. Truck broke down and sat until a couple days ago. I have great pedal when engine is off. As soon as I start the engine, I lose all brake pedal?

 

[SUBURBAN5]

Have you checked for any leaks?

 

[Pappy G]

Yes , no leaks.

 

[SUBURBAN5]

I hate to blame you but with all that hardware replaced it's possible you have air trapped. Also it's very common. I actually may be following my own advice soon because I just changed all my hardware too. However instead I did not replace my mc because that's fairly new and was done by dealer. But it's very easy to have it air lock in the abs module. Do you have any lights on?