Duramax Lifetime Supporter
Join Date: Aug 2012
Location: Carson City, NV Proud Participant, Federal Witness Protection Program
Hello and welcome!
A chronic problem with LB7 injectors is trouble with the ball and seat in the internal return circuit. One or more may become badly worn and instead of the typical return flow, diesel fuel is hydraulically “short circuited” and correct rail pressure cannot be established.
A simple test may be done by going under the truck and disconnecting the return fuel line between the fuel cooler and tank (often impossible due to corrosion, so cutting in is necessary) and measuring fuel return flow into a container with the FICM fuse pulled and 15 seconds of cranking.
The test may also be performed topside on a bank-by-bank basis, but I believe if total return is incorrect, just do all injectors at once.
Consider SAC vs VCO’s.
Search the forum for specifics and a better pic of injector innards.
Other issues may cause low rail pressure, but this is often low hanging fruit.
2003 GMC Sierra 2500HD SLE ExtCab CA Emissions; 155k; Allison 1000 w/Transynd X2 Flush & Fill; 8' bed; AFE/CAI; MBRP 4" Exhaust; Side Tint, 33% VLT, rear, Limo; Smittybilt Stainless Side Nerf Bars; Sprayed-in Bed Liner; MadJack Fuel Filter Access Door; Regular Used Oil Analysis (latest available on request), Blackstone Labs; EGT/Boost Gauges; Dual Chrome Dipsticks, JC Whitney; Stainless Steel fuel filter head bleeder screw; New WP and Hydroboost; Billet Aluminum Fuel Filter Housing Spacer; Professionally repaired instrument cluster (new steppers and lamps); Does anybody ever read this s%#t?; Injectors under warranty @ 70k; 2nd set DIY @ 155k