Did the o-ring/spacer/o-ring come on a plastic "plug"? You're supposed to push the entire thing into the fuel line, remove the plastic plug and then press the line onto the rail. If there is no plug, place the spacer on the rail then an o-ring, press the line on, remove the line (o-ring and possibly spacer will stay in the line), install the last o-ring in the rail and push the line back on. Make sure to lubricate the o-rings.