There are only a couple of reasons to be in open loop mode:
1: Bad/disconnected O2 sensor
2: Cold engine
3: WOT switch engaged.
2 & 3 both relate to the same wire being grounded
If you're crazy rich the dwell meter will fall to nearly nothing as the system attempts to lean out the mixture
If you're crazy lean the dwell meter will spike high
AFR on a warm engine stuck in enrichment mode will dip as low as 10:1
If the dwell is fixed in the middle and doesn't vary the system is electrically stuck in open loop. I wouldn't chase down a fuel pressure solution until the electrical component has been ruled out.
Disconnect the WOT switch and see if the dwell starts to vary (WOT switch stuck). If not, see if the light green wire on the connector has continuity to ground (thermistor stuck grounded).