This probably wouldn't be your issue but I'll mention it anyway, just in case. My LondonAire is also on a Spartan Chassis with the 12500 Onan. I had an issue where the generator wouldn't run for more than 60 seconds before running out of fuel. At the same time, I had been servicing the Aquahot and the Aquahot filter was not installed. With the filter/separator off of the lines going to the Aquahot, turns out the system couldn't pull a vacuum on the fuel lines and the generator would stall. It took me a few start / stalls to figure this out. In retrospect, I suppose it was obvious.