Below is the reply to fnlatch's Private Message to me. BTW, I would not think this is an air related issue. Yes, air restriction can limit power, but not much air is required at idle (low RPM and no boost), so dying under those conditions would suggest other than air- related issues.
Actually, this would make a great post-- we have several diesel techs on the forum. Copy it and paste a new thread under "engines".
But were it mine, I would start by removing the primary fuel filter for the engine and the fuel filter for the generator. Dissect them and see if there is contamination.
The other option is that there is a problem with a leak in one of the fuel lines on the suction side of the lift pump (line from tank to primary filter and primary filter to lift pump). Being on the suction side, you would not see fuel leaking out, but air can get in. Same for generator circuit.
Now, as to engine stopping-- did it just die, or did it miss before dying. If it just died, may be an electrical issue.