I have a 1976 W100 with the in frame plastic gas tank. When I towed it to my house and got it running, it drove. Complete engine rebuild, new mechanical fuel pump, Holley 500CFM with manual choke, new fuel line. Runs perfect off a gas can. Tried priming with fuel into the bowl but still no fuel from tank. Don't get why it drew fuel with the original build but not now. I have not pulled the sending unit yet. Tips, thoughts?

 

Kinked the steel line or the hose is no good at the tank sender....

 

I replaced the entire line, nice and smooth corners, no kinks.

 

I would try blowing air front to back in the fuel system, is it out of gas?

 

Read the service manual and do the checks on the pump. One important check is the vacuum test. A "new" pump does not mean a "good" pump. You didn't say what engine? But you could even have pushrod issues with a B/RB or a loose / failed pump cam or pump arm on a SB

Suspect a gummed up pump pickup. Make sure the connection hoses are in good shape.

 

Must be the pick up in the tank is broken in that case...

 

Sorry y'all it's a 5.2 318 LA. It has about 5 gallons of gas in it. I'm going to pull the sending unit this weekend and see what that looks like.