88 VW Jetta GLI - starting problems

Have an 88 VW Jetta, some days it will start/run strong no problem, others days it will crank strong but not start/run. I've replaced cap,rotor,alt,battery,plugs are good etc. Sometimes if I wait a few hours it will start or not at all. There is no clear pattern being developed. Any thoughts are greatly appreicated. Like many I can't work without my car. Thanks for reading :banghead:

Not an expert, but it may be something in the fuel system. Do you get a whiff of gasoline when you approach the car? There may be a pinhole leak that's draining fuel from the line when it sits overnight. Without fuel, the fuel pump will seize up when you try to run it dry. Just my $2