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TriumphGuy's avatar
TriumphGuy
Explorer
Jul 27, 2016

Onan 7k gas generator - long cranking time on re-start

Hi folks,
Just back from a two week trip, had lots of generator use for the roof A/C.
Normally I've started the generator when "cold" and (after I prime it) it starts up after about 2-3 seconds. But this was our first long trip and I was shutting it down at gas stations and then re-starting after filling up, about 10 minutes later. Even after priming, it would take a long time to start. For example I'd hold the start button down for about 10-15 seconds and then it would start. Sometimes it wouldn't start after that amount of time, and I don't remember what duration the manual said about "not cranking too long" (only that it did) so I'd go about that long and then stop if it didn't fire up and then try again a few seconds later. Eventually it would fire up and run well and we'd be on our way.
Model is 7HGJAB-900D Spec: D. 221 hours, just had an oil and filter change before the trip, air filter is due but it looks clean.

Ideas?
  • If it was just running recently, you shouldn't need to reprime the generator. I don't think on the usual Onan setup it would cause problems (e.g. flooding) since it's really just filling the carb bowl with fuel and extracting any air from the gas lines, but on other engine designs it very well could cause flooding, just as using the choke could.

    Perhaps you're encountering mild vapor lock?
  • I've wondered about vapor lock. I need to take a closer look at the fuel line routing for the generator.