i have an 88 1 ton custom delux with a 5.7 (350) it is loosing injector pulse i have replaced fuel pump,modul,distributer and pick up also the computer,the truck will run great for about 30 seconds then injectors cut out.if you try to start it no pulse at first then fires right up 30 secs later same thing. if you got any ideas please let me know
                thx jeff.  

some of you will know who i am from the other forums...

for this one....    i would dig into the wiring around the column .... look for an alarm relay hooked to the wrong wire...  i have seen this several times...

here is a diagram from autozone that should help...

http://econtent.autozone.com:24991/znetrgs/repair_guide_content/en_us/images//0900c152/80/08/f3/d2//large/0900c1528008f3d2.gif

if you notice the injectors are fused with a separate circuit... are you also loosing power to the injector... or just the control circuit from the ecm....    and are all the ground wires on the motor properly... check please... they may be on the back of the heads.... (battery grounds are from the battery to the body and the block,  the ecm grounds are all to the intake and heads....  and tend to get left off.... the ecm is otherwise isolated from all other grounds....)

there are more diagrams on the autozone site...  

Did you scan for trouble codes? I used to have an '85 Caddy that would stream trouble codes just by holding the heater and A/C buttons down at the same time. I'd look up the number, and it hit the problem right on the nose every time. Chevys are harder to access, but look into scanning codes before you buy every part in Pep-Boys trying  to make a good guess. And Wayne, thanks for taking the time to jump on here with some good advice, and Web link.