Thor Forums

[dkoldman]

Originally Posted by Wiley1

Darn. Now you've made me pull up the Onan QC 4000 owners manual.
It lists a 5-step starting process which I will condense to:

1. Turn off all high-current appliances like A/C units.
2. Prime by holding Stop.
3. Start by holding Start.
4. Allow the generator to warm up for a few minutes.
5. Turn on A/C units and other larger loads.

It does not say what the "normal" cranking time should be before the generator typically starts. But, IMHO, that is a function of how long it has been since the last time the generator was started. Why? Because my Onan generator has a carburetor and a float chamber. One side of the carburetor is open to the atmosphere and the other side leads to the combustion chamber. The longer the generator sits without being run, the less gasoline will be available in the float chamber for starting. That fuel must be replaced, either by priming or cranking or both.

Perhaps your generator starts quickly, without priming, because you run it every time the thought occurs to you.

In my rig, the generator is less than 12 feet from the gas tank.
When the generator is cold, and not used for a several weeks, it takes about 7 seconds of cranking to start after using the Prime function.
Without using the Prime function, it takes up to 25 seconds to start.

I love my Prime button. I believe it exists to shorten the cranking time. Of course it is possible to start the generator without using the prime button, but why would you?

The OP asked whether his Onan is behaving "normally". I believe it is. The manual backs me up.

If your manual says to Prime every time, then there is Operational differences between an Onan 4000 and the Onan 5500? I will take my view out the equation and share what my manual for the Onan 5500 says.

Note: It actually does tell you after 30 secs of hold the Start button, it will send an error code, and it clarifies to only Prime when out of gas. (it says IF out of gas)

With that said, since OP has a Onan 4000 I will yield; as I assumed they were the same? If my Onan 5500 starts to requires me to Prime every time, I will ask my Dealer about it to see what happened. Especially while it is still under Onan Warranty.

Note: OP did say he was exercising his unit by the manual, and I my RV was at a Dealership for 2 months and it still started right up.