Clark, you may have one or more glow plugs that are not working. If you have not replaced the plugs in awhile, you may want to do that job. You might have a glow relay problem, though I would personally start with the plugs if you have not done them in awhile, particularly if you are starting in colder temps. I have done my plugs twice without removing the injectors. I have a 126 chassis and am not sure how tight of a squeeze it is on your chassis (I believe that you are the 123).
Definitely go with the Bosch plugs. You should be fine starting it throughout the summer, though you wanna take care of it before winter for sure. I have started mine in -23 C, roughly -10 F.