89 chev 3/4 t van.350 auto 96000kms.it,s starts 30 sec. dies

this van has been in storage 2 years, i go to start it,it runs for 30 seconds dies." to restart"i must turn the key off,runs dies.about the forth time i,m good to go. the items i have changed are new distrubator,[complet] fuel pump,filter, temp sending unit, cga valve,spark plugs, had the timing set by computor.I get terribal fuel milage , when it runs ,it,s perfect. this is a camper van and i,m afraid i can,t trust it not to start. the mechanic said to change the coil that might help.also the fuel regulator valve, he also said to change the key starter switch. I have spent over $1,000, I,AM 71 and need some one that" knows" p/s their are no vacumn leaks