P1261 - glow plug #1 control circuit low.
There is a mesh sock filter inside the tank. If your filter head pumps up good and tight and you bleed the filter head and get no air, filter in tank is probably OK? Bet you got some air in the fuel supply to the injection pump....

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Supporting Vendor and Moderator of LOST05 Jeep Liberty CRD Limited 
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount98 Dodge Cummins 24 Valve