There are 3 ways to fix this problem. You can either rewire the entire ignition system, Run a push button, or run a relay. Take the clip wire off the starter, run that to the relay, and run a hot line from your battery to the relay, and another hot line from the relay to where the clip wire was. Then ground the relay, and put it somewhere safe. The extra resistance in the lines wont affect the ability to set the relay off like it will in engauging the starter soleniod. This is why u can "jump" the starter and fire up easy, but it wont always fire. Im also willing to bet that the times it doesnt want to start normally is when its humid out, and the wires have even more resistance.