2001 chevy express 3500 no start no link to odb2
 

One morning, van just cranked, i heard no power to fuel pump so i replced it, no change. Cant link with odb2 scan, no power to fuel pump, the pump will 'thud' every so often when key is turned,, getting power to odb port. ,ground on pins 4 and 5, only. .1 volts on pin 2, any ideas?? Thank you

Check the easy stuff ... fuses.

I checked them

Next I would use a multimeter or test light, and see where along the fuel pump circuit the voltage stops. You can find diagrams here:

BBB Industries- Premium Alternators, Starters, Power Steering Products and Turbochargers | TSB and Wiring Diagrams Database

how did you "check them"? best bet is to use a tester of some sort and not visual

I did find a blown fuse, dome light but it made no change, i found that if igo back and forth with the key i eventually get the hum from the fuel pump and the fuel gage activates, when i get that iturn the key to start and it starts right up and runs fine. Whats going on here?, ignition switch?

Who knows. More troubleshooting required.

At least hook up a light to the pump and see if it comes on every time.

It doesnt come on, until i goback and forth with the key a few times

You already said the pump isn't coming on. I'm suggesting putting a light there. If the light comes on and the pump does not, then you've isolated the problem. It's called troubleshooting.

No power to pump until a few turns off and on