I have a 1981 El Camino. My right turn signal will blink but the left will not. I checked the rear bulb, front bulb, and side marker bulb and they all work. I can't figure out why they won't flash. The lights are on when the signal is activated just not flashing. I also noticed that with the park lights on the right turn signal flashes slower than it does with the park lights off. How do I figure this out?

Change the flasher relay located under the dash, it's cheap and just might take care of the problem. Good luck

Try switching on the Hazard Lights. All four should light up and all should have similar intensity.
Chances are one bulb is either installed incorrectly or there is a problem with a lamp socket. If you find one lamp that isn't lighting properly, take a close look at the socket to see if it is worn or damaged in any way.