92 B2600i won't start
 

I have a 92 B2600i that will not start unless I pull the boot off the 3rd spark plug and ground it to the compressor bracket while my friend turns the ignition key. I checked the coil resistances for the primary and secondary coils in addition to the distributor rotor. I also double checked the battery ground. Once started the truck runs great and without problems until the next starting attempt. Is there anyone here that would know where the problem is???