First off, is the check engine light on at all? If so, gain access to a code reader and obtain the codes, and post them back up here. If your truck truly is a 96, then it is the first year of OBD II, so of course you will be looking to borrow a OBDII code reader. IIRC, autozone, or many of the chain auto parts store will read codes for free, if the truck can make it there.
The most common issue on the electronic pumped 6.5Ls (94-2000) is the PMD (Pump Mounted Driver) it is the little black box on the drivers side of the injection pump with one wiring harness hooked to it. The previous owner may have relocated it to the bumper or the intake.
When it is going bad, it will do all sorts of crazy things. Post up a description of any stalling, rough idle, etc, basically anything that differs from a normal idle and acceleration. Any details are usually important, so feel free to describe anything that is unusual, or seems unusual to you.
Do you plan on keeping the truck for a while? What is its primary uses? knowing this will affect advice given on parts purchases, etc.
also, can you fill out your signature with the specs of the truck, like 2wd/4wd 3500 SRW or DRW, RC, EC, CC, 5spd or auto, and if DRW 3500, did it start life as a pickup (v shaped frame, as viewed from rear) or as a chassis cab (straight, parallel 34 inch spaced frame rails, commonly with dual tanks) etc. it does make a difference!
99 Chev C3500 6.5L NV4500 14 bolt 2wd 4.10 130K White Ext, Gray Int. RC159.5" WB DRW Chassis Cab with utility box Runs Great, building up
96 GMC C2500HD 6.5L NV4500 14 bolt 2wd 3.73 240K White Ext, Blue Int. ECLB 155.5"WB SRW Pickup runs bad, getting motor right now
95 GMC C2500HD 6.5L NV4500 14 bolt 2wd 4.10 135K White Ext, Grey Int. RC 131.5"WB SRW Pickup with utility box runs strong, yet huffs on 1 hole
95 Chev C3500HD 6.5L NV4500 D80 2wd 5.13 132K White Ext, Grey Int. RC 159.5"WB DRW Chassis Cab with flatbed bad heads, needs motor re-do
94 GMC C2500HD 6.5L 4L80E 14 bolt 2wd 3.73 300K White Ext, Blue Int. Suburban needs engine
91 GMC C1500, 6.2L SM465 10 bolt 2wd 3.42 59K Red Ext, Red Int. RCLB 131.5"WB SRW Pickup needs injectors, oil cooler lines
91 Chev C1500 4.3L 5LM60 10 bolt 2wd 3.42 ??K White Ext, Red Int. RCLB 131.5"WB SRW Pickup needs...alot
98 GMC C3500 5.7L Vortec NV4500 208K down right now, needs head gaskets (dex cool claims another set! )
92 GMC C3500HD 6.5L Turbo NV4500 160K needs exhaust system and oil cooler lines
93 GMC C3500HD 6.5L Turbo 4L80E 260K had a crate 6.5L sometime
All above are 159.5" C&C, 10'-12' flatbed, Summit white, RC, SL trim, 2wd
96 GMC C2500HD SL ECLB 6.5L 5spd 2wd. 215K (sold to dad, ran good for a bit, started missing at idle, had blowby since purchase
84 Pete 362 COE, 300 BCIII RTOO 13 spd Fuller (3 OD ratios, hard to find) Single axle tractor, air seats, cab, suspension, OEM twin 200 gallon tanks.
74 Pete 352 COE, cat, 13spd TS, B&H grain truck
90 Marmon 57P long hood conventional, 60"flattop, 12.7L60 Series, 13 spd fuller, TS tractor
76 Marmon COE 8V92T 13spd fuller, TS B&H grain truck
95 IHC 9600 COE M11, 10 spd, SA tractor.
Last edited by GM Guy; 11-28-2010 at 06:22 AM.