I have a 2002 Freightliner/Thomas with a Cummins 5.9 engine.
I have heard that the lift pump is poorly sized for the engine, and is likely to fail sooner or later (this bus has been through about five of 'em per the records).
The bus mechanic who sold the bus to me said the school district put in a low pressure sensor on it.
But I don't know if they did, how it looks in the cab, or what the pressure is. I borrowed a fancy gauge from the car parts store... and couldn't find the Schrader valve.
Here's a photo. I'm guessing they popped off the Schrader valve and installed a sensor - and the green piece is the connector for the wire into the dash.
If I have that right, I should be able to ground that (single) wire with the engine on, and get a light or a buzzer in the cab, right?
In the image I've labeled what I think is the sensor, and its connector ("B"), and where I think the Schrader valve was.
...and if you're still with me, is Connector "A" a water-in-the-bowl sensor?