I put a newer used 4.3L vortec vin w in a 96 GMC sierra and it's the same engine and all the lights and electrical stuff work. The check engine light and air bag light is on. It turns over but it won't start. I thought it might need more gas but it wasn't that and I put dry gas and I here the fuel pump turn on and off. I thought it might be fuses or the distributor but I don't know.

Test all under dash and under hood fuses with a test light or multimeter:

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