Green’s Dictionary of Slang

full of... phr.

SE in slang uses

In phrases

full of crap (also full of bean soup, full of feces, full of prunes)

(orig. US) contemptible, stupid, nonsensical.

[US]J.L. Kuethe ‘Johns Hopkins Jargon’ in AS VII:5 332: full of bean soup / full of crap / full of prunes—expression of disbelief or contempt.
[US]J. Steinbeck Grapes of Wrath (1951) 54: Willy was full of crap.
[US]H. McCoy Kiss Tomorrow Goodbye in Four Novels (1983) 237: ‘You told me once you didn’t know much about guns.’ ‘Oh, you know I’m full of crap,’ I said.
[US]R. Graziano Somebody Up There Likes Me (1956) 250: They are full of crap.
[US]H. Simmons Corner Boy 148: Aw, she’s full of feces.
[US](con. 1930s) R. Wright Lawd Today 61: Aw, you niggers full of crap!
[US]A. Hoffman Property Of (1978) 77: You’re full of crap.
[US] ‘The Open Book’ in G. Logsdon Whorehouse Bells Were Ringing (1995) 109: So it’s high time somebody debunked him; / he’s so plumb full of crap.
[Aus]Penguin Bk of All-New Aus. Jokes 147: Why are men like toilets? They’re either vacant, engaged or full of crap.
S. Berkun Art Of Project Management 451: So, if ever people complain that requirements and problem definitions take the challenge out of problem solving, know that they’re full of crap.