My 94 Tahoe was having a no start and just a blink of the glow plug light. I built a glow plug control since my pcm wasn't sending the relay the right signal on the yellow relay wire. I built one that I wired to ignition that comes on only for the first 12 seconds then off till the next start. It turns on my glow plug controller each time. Still no start next found the optical sensor in the injection pump was flaky. Replaced with one from my old pump. Running again and my pump only had 4000 miles on it.