i took my 78 into the shop and the mechaninc told me that the glow plugs and injectors often start to go around 150, 000 miles. mine had 187 on it with the originals. he may have been pulling me a bit, im not too familiar with diesels, but the new injectors made a world of difference. a bit costly though, 50 a piece for rebuilts. so yeah, id check those out. good luck!