I recently did some work to my '79. It has a stock (rebuilt) Isuzu with a weber carb. It began to fail at idle; idle became rough and driver would need to way over pump the gas pedal to keep the engine running. This has happened before. As a result of that last issue I changed the fuel pump and changed all the fuel lines, the coil and all that goes with the ignition (points, condenser etc)
When it began again I decided to check continuity in the wires. I found that not all the plug wires were good. I changed them and went thru the points, condenser etc again to find that there was no spark, at best intermittent spark. I threw up my hands and, with head hung low, took my baby to a mechanic.....
The brand new condenser was bad. I spent $180.00 to find this out.
Moral of the story: If the condenser is bad there will be no spark.
