1997 Mercedes Benz S600 53k miles
Problem: The car cranks, but as soon as it tries to start, it immediately dies. I am unable to determine the cause of the issue.

Actions Taken So Far:

1. Checked all fuses and relays.
2. Scanned for error codes; found P1463 (Air System Malfunction, LH). However, this code has since disappeared after I disconnected the battery a couple of times. Currently, there are no stored codes.
3. Inspected all vacuum hoses with a smoke machine and replaced any cracked or leaking pipes.
4. Checked the coils and spark plugs—everything appears to be in good condition.
5. Measured fuel pressure, which was low initially. After replacing the fuel pump and filter, the fuel pressure is now within the proper range.
6. Replaced the crankshaft position sensors.
7. Used a noid light to check the injectors; I observed a flicker when the engine attempted to start but did not see any light during cranking.
8. Sprayed starting fluid into the intake, and the engine briefly started. This led me to suspect that the issue may be related to the ECU sending a delayed signal to the injectors.

Thoughts: Based on the observations above, it appears that the injectors only receive a signal when the engine is attempting to start, suggesting that the ECU may not be properly controlling the injectors during the cranking phase. The vehicle only has 53,000 miles, and everything else seems to be in good working order. I'm uncertain why this is happening and would greatly appreciate any insights.