1990 F150 5.0L won't start after 15 months.

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I have a 1990 F150 5.0L V8 RWD. I had it tuned up and it was running fine last time it was started. The gas tanks were almost empty so I filled it up with $20 worth of gas and half a bottle of fuel stabiliser before I started it last weekend. I also took the air hose off the fuel injector air intake and sprayed some engine start in. It fired up but won't catch on and stalls. I tried for a half hour trying to get it running but no luck. What do I do now? Is there water in the gas line? How do I flush it out? Thanks!