Need some pump advice.
 

Ok guys here's the thing. I drive a 96 chevy one ton with a 91 twelve valve in it. Every time I kill it, it get air in the lines somehow but it is not leaking any diesel. I replaced the fuel fictures and that helped some, but the problem is still there. I was just wondering what ya'll think about it.

I'm no expert on 12V trucks, but as I understand them they also use a lift pump. Air getting in with no leak generally means that the leak is somewhere before the lift pump. Pre lift pump it is all vaccuum pulling in, after LP it is pressure that would push out, is the simplest way to explain it. So someplace between the fuel pick up in the tank and the LP.

I Agree Check for Dry Rotted Fuel Lines

DM

Fuel lines tend to develop very tiny, almost microscopic holes that let air in. They dont leak fuel so you cant see it. Usually the let enough air in to cause you to lose prime.

If you havent changed the lines before...its a good place to start. I would recommend using only diesel rated fuel hose. If you use the other stuff you will be changing them again in short order - and its not exactly a fun job.

Deffinately not a cheap job either with all the fittings included.

I worked on a couple 12v's that had soft lines running just in front of the firewall. They're a pain to get to, but if you can get them pulled off and run air into them the cracks should show up. In both cases we replaced it with braided steel fuel line and the problem went away. It also made it so it shouldn't go out anytime soon until the soft lines.

Whats the Status on this ?

Through PMs Texas Crossbreed has informed me that problem was both lift and injector pumps. And he has it fixed. Thanks guys for the help, keep it coming.