Aqua Hot not igniting on Monaco Dynasty

odds are you had a air bubble in the fuel line between the Filter and the Unit. It does not take long for a unit to cycle off on Diesel. It probably ran just long enough to use the fuel between the Filter and the Aqua Hot. Then setting a month, caused the air bubble to block off fuel. I was going to post previously. I was going to ask if you had a strong smell of Diesel by the exhaust OR you had Diesel dripping out the down pipe elbow for the exhaust. THAT would indicate fuel IS getting to the unit, but the spark is NOT happening. When it failed to start, IT DID time out and the webasto shut down after a few minutes? It should have. I usually have to run a flooded unit up to 1 hour to get rid of ALL accumulated residual diesel to get rid of all white smoke. And NO, the fuel nozzle should not have a problem from a month of inactivity. ALL Aqua Hots, need to be run monthly on Diesel and activate the furnace section also. This keeps the furnace section check valves from sticking. THIS is a usual cause when the Aqua Hot Furnace section is not used for a long time. Doug

White smoke is a result of accumlated fuel during the non start times, maybe not a fuel issue. It will likely happen again. Suggest tighten/clean all wiring connections and it could be a component failure. Intermittent failures can be hard to isolate.

White smoke can also be due to a worn nozzle, not your issue as it cleared.

Thank you always for the helpful input on the forom. that I really appreciate all the smart posters out there regarding the aqua hot that would not ignite. I kept turning it on yesterday about 5 times, and each time it didn't ignite, I would turn it off. finally at the end of the day it popped on with a big cloud of white smoke And it continued very smoky for about 4 or 5 minutes and then cleared up. since then I have successfully turned it on each time I'm not sure why all of a sudden it started to work maybe, there was air in the fuel line but it's working great now.
Many thanks. Hope it saves me a service call.

It could be a air leak with the new fuel filter gasket or a loose wire connection.

I have had 2 different Aquahot units with the same issue. One was very intermittent. What I found was the control thermostat sensor would build up a little resistance and keep the unit from firing. Every time I replaced it . . . problem gone. Page 22 below

Aqua Hot Manual