Yeah, something isn't right. I've heard reports of people getting down into the mid 200s and their 3Bs are still running, albeit poorly. Much below that, you won't have enough compression to ignite the diesel.
Just to be sure, here are the steps for doing a compression test per the FSM:
1. Warm up engine
2. Remove all glow plugs
3. Install tester
4. Without EDIC - Pull the stop button all the way out
4. With EDIC - Turn the starter switch to LOCK position and then disconnect the EDIC motor wire connector
5. Depress the accelerator pedal all the way down
6. Measure the compression pressure while cranking the motor with the starter
*cranking speed 250 RPM
Compression
STD 427 PSI
Limit 284 PSI
Difference less than 28 PSI

Just to be sure, here are the steps for doing a compression test per the FSM:
1. Warm up engine
2. Remove all glow plugs
3. Install tester
4. Without EDIC - Pull the stop button all the way out
4. With EDIC - Turn the starter switch to LOCK position and then disconnect the EDIC motor wire connector
5. Depress the accelerator pedal all the way down
6. Measure the compression pressure while cranking the motor with the starter
*cranking speed 250 RPM
Compression
STD 427 PSI
Limit 284 PSI
Difference less than 28 PSI
