97 blazer 4.3 having problems starting. We drove it home one day and next morning no start. It backfired like it had jumped time spit and sputtered through the throttle body. Went back in for a little while maybe an hour, turned key over and it fired right up. Ran like a top, no power loss, hesitations nothing different. Drove the blazer 20 miles shut it off and went to start it and same backfire and spitting. Turned key off and back on it fired right up. Has done this several times so we decided we can't depend on it so let it set a few months. Tried again and same thing. We thought maybe the converter was stopped up so we took it off and it started three days in a row several time day no problem. So welded in a pipe in place of that and put on new muffler as well, drove 10 miles last night and this morning wouldn't start. Fuel pump and filter is new less than 6 months old. Ac Delhi pump. Check engine light isn't on either. Please help

 

Have to done a fuel pressure test???? U should really start there....just because it was replaced doesn't mean there isn't a problem with the fuel system...

 

Put a scanner on it and it gives a p0123 and a p1345. Could the cam sensor be the problem? We have a cam sensor that we know is good