fuel pressure issues

[rennat_2006]

We just swapped a 2000 5.3l into my little brothers 79 k10 longbed with dual tanks. We used a walbro 255 pump mounted on the frame rails plumbed into the factory fuel lines and plumbed the return line off of the engine into the factory return also.

Ran it for awhile and it seemed to run fine then started acting up, found that the fpr on the fuel rail was blown. Replaced that and it ran fine for awhile again then started throwing rich codes and running very poorly. Passenger bank was so rich that you could see raw fuel running out of manifold. Put fuel pressure gauge on it and found fuel pressure was 105 with key on engine off then would drop to 30psi. Also found fpr was blown again. Figuring that because of the pressure we have injectors stuck open and is also the cause of blown fpr's.

Little brother was talking to guy who tuned computer for him making sure we didn't have maf sensor issue or something then we found the fuel pressure problem. The tuner said that those trucks have a restrictive return line into the tank which is were all of our pressure problems are coming from. Figured id ask the experts on these trucks to confirm this for us before we dig into it and if it is true what have others done in this situation.
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[usmcchevy]

My only guess would be the return line being too restrictive. Let us know how it turns out.

[rennat_2006]

little brother took the bed off of his truck yesterday and dug into the sending units. Found that the return line was very restrictive, He drilled it out to the size of the hose i believe it was and that took care of the problem. Fuel pressure only goes up to like 55-60 key on engine off.