Why won't my truck run

im getting a Blue/White spark from each wire and plug and plugs look to be firing good

Ok, here we go ... We have good compression on all cylinders when tested with a gauge... We have good fresh gas with no water in the tank... We have good hot spark... We know we have gas in the engine , you put some there. Since we have good compression, we assume timing is correct... 'IF' all that is true.....Only thing left is a completely blocked exhaust system!!!!... Not even a backfire when cranking????

I unhooked the exhust from y pipe, rechecked timing . put code reader on it and it came back No Codes found... Can the switch b causing it ? no backfire either