Leaks only while manually priming

[Deflush]

Hey guys I have a 89 d350 and it has recently began losing prime. When i manually pump the lp lever i get a bubbly hiss followerd by a steady drip from the lower rear of IP just behind the kill solenoid. When i get her fired up i can no longer see a drip. Ive done some searches on this and haven't found any definite answers and I'm having a hard time finding said drip while pushing the LP lever. Anyone have any ideas?

 

[DVolk]

I'd check for loose lines ?