Help!! Branch tube O-ring blowout

[delmer]

Can someone please explain why twice in a row the branch tube O-Ring blows out on a 2005 6.0 with the STC upgrade. Replaced. Excellent pressure. Everything starts fine and then shuts off after 50 miles and won't build pressure.
O-ring between upgrade fitting and branch tubes blown out again.

Very very frustrating.

[sinner6.0L]

how are you installing the pump? I would be looking at the branch tube being tweeked or possibly the updated fitting being lined up wrong (not deep enough or not level)

If the fitting doesn't line up perfect with the branch tube you'll need to tighten it down snug first, then pull the pump into position