I have A 98 1500 with vortec 5.7L that was running fine one day and day and a half later wouldn't crank. I have put Dist. Cap, Rotor button, ignition module and today I put pick-up module on it. It is firing but it is A yellowish blue spark. Thought at first the fuel pump had went out again but has 56-60 psi. So then pull plugs again and found weak spark. Another thing about it is thers is no engine light on in dash? Any suggestions ? What else could it be? Thanks