My 1989 240 won't start. Battery seems strong and it turns over fast.

Here's the history:

1. Car was running fairly well, but has had intermittent issues with stalling at stop lights. If it did stall, the car would restart immediately. Then one day all of a sudden, it won't start in the driveway.

2. Recent troubleshooting prior to no-start showed OBD codes 2-3-1 (mixture), 3-1-1 (speed signal), and more recently 3-1-2 (knock sensor). I don't think these would cause the car not to start, however.

3. No-start diagnostics so far: 25-amp blade fuse shows 12+ volts on both sides, I get spark from central distributor lead, both fuel pumps run when I jumper fuses #4 and #6. Car won't start with fuses jumpered.

4. Potential clue? When I try now to get codes from the OBD it doesn't respond. I get a red light when I press the button, but it doesn't return any blinks. What's the deal there?

Where to go from here?

Thanks...