GM-GMC: 1990 GMC 2500 4w drive will not start, gasoline engine, gmc truck

Question
My 1990 GMC truck stopped while I was driving. I have not been able to get it to restart. There seems to be no spark, it will not take a jump or fire when gas is added to the carb. I have replaced the Distribuator thinking maybe this was the problem - still no luck. Can you give me any tips on where else to look.
Thanks

Answer
A gasoline engine needs three things to run:  Spark, fuel, and compression.

If you are absolutely certain that the new distributor is providing spark at the right time (was it installed properly?), and you have added gas to the carb, that leaves only compression.

If you have a lot of miles on the engine, the timing chain and gears may have worn to the point where they jumped out of time.

A compression test will verify the problem.  All cylinders will read low compression during a compression test.