[Grady Clay]

Jon (melman),

When it won’t start, you should confirm it has ignition spark.

Do you have access to CIS fuel/control pressure gauge?
This will tell you where to look.

From your symptoms, I suspect fuel supply issues.
A good first step would be to drain all the fuel and remove the screen filter in the center-bottom of the tank.
Inspect and clean the screen.
If even the hint of debris, summarily replace the fuel filter in the engine compartment.
Refill with fresh premium gas.
Even if this does not cure the problem, you have done some useful maintenance.

Another possibility is the fuel pump is failing.
With the fresh gas, make yourself a long hose that connects to the outlet of the fuel filter.
Route the hose to the gas fill on the LF fender, allowing some slack.
Run the fuel pump continuously circulating the fuel (you may have to raise the sensor plate in the CIS to get the pump to run).

Take a ‘calibrated’ container and measure the fuel flow for some exact (measured) time (~1 minute).
Calculate the flow rate ((volume collected) / (time)) = (flow rate (ml/min)).
Spec is 1500 ml/min minimum.

This will confirm the pump is capable of flowing the necessary fuel.
The only way to properly diagnose a failing fuel pump is to measure the pressures while the 911 won’t start.

There are other possibilities but this will cover basics.

Best,
Grady