I may be getting ahead of myself. I haven't done any testing, just some guessing. I have a 1987 4x4 LE van and it will usually start when it's cold, and then after about 20 min of driving it starts to misfire and will eventually die. I thought it was the fuel pump, 'cause I had run it out of gas a few weeks ago, but a friend said check the igniter. (The fuel pump is pretty new, like 1k miles on it.) I think you need an oscilloscope to do this?

I have the factory repair manual and it has no info about performing this test. Also, This part is very expensive, like $400 from O'reileys. Is there any cheaper solution if this is the problem? Like Petronix with an older points distributor?