Ok so i am drivig and it slowly starts runnig like crap. Pull over and check fuel pressure. Sitting at about 20 psi (wtf). So i start checking inj screens -all good. Then held rpms at about 1800 and it starts loosing fuel pressure. Zero leaks. All stock ls w/ benen fuel rail, b&m gauge, oem fpr, 255 walbro (new less than 200 miles new sock filter also) I cant do my normal inj test of pulling and watching for sticky inj as it only does while running. I am thinking fpr or sticky inj. Thise are only things i know that would cause fuel pressure drop. Pressure drop is in less than 15-20 sec after start up. So it is very sudden and it drops all way down to about 15-20psi. Car is also running a trick flow inline filter (metal filter is clean), i have also pulled screen filter and tried with same result.



Ideas???

 

Ok so i tested with inj out and zip tied to rail, cranked car. All 4 inj fire/spray as they should and not leaking/ dripping. It does loose pressure after cranking. Could pump be leaking back internally? It is a REAL walbro 255lph and has around 200 miles/3weeks old

 

FPR or possibly fuel check valve in pump, although the check valve should not have an effect while engine is running, [pump running]. 94

 

Well i have tried 3 oem/1b&m adjustble fpr and no diff. Also replaced fuel line from hanger to pump.