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Old 04-23-2021, 01:54 PM   #15
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My O4000 Microlite is in another state right now. But I can assure you that the rubber covered start/stop switch on the generator does not illuminate anything at the generator.
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Old 04-23-2021, 02:36 PM   #16
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Quote:
Originally Posted by F4Gary View Post
In looking in the Q4000 Owners Manual pdf it appears it can only be primed with the switch that in on the genny and not the switch mounted inside the coach.

The Control Switch is labeled Start and Stop/Prime and has the little yellow light. The switch on the dash does not.
It is about to storm here, but as I was going to the mailbox I stopped by the RV and decided to start the generator for a few minutes. I am in agreement that it is certainly possible that my generator remote is different than some others (likely in fact), with that in mind I looked on Ebay for a replacement onan generator remote start switch and some of those show "Start Stop" only (like mine but different style) and some show "Start Stop\Prime". I tried to find a wiring diagram that indicated a difference between the two styles but they all seem to be wired the same so perhaps it is the controller on the generator that makes the difference. In any case, on mine, if you hold the stop button down for more than ~3 seconds it lights up and as today (I left the door open) I hear the fuel pump running after 3 seconds of pressing stop. I may not have even needed a prime today though as I had it running a week or two ago, in any case, I held the stop button down, 3 seconds later it lights up as in the picture, held for 15 seconds and pushed start and the generator started right up after maybe 5 seconds starter run time. So all in all, the remote start prime function certainly may be different in certain years and certain model remotes.

Also, as I was thinking, I think the need to prime is related to whether or not the carb fuel bowl is full, half, or empty, which got me to thinking why and where the fuel went. I searched on gasoline evaporation rate and found that there is not specific rate of evaporation as it all depends on the fuel blend, the altitude, the temperature, along with many other factors, so what I suspect is that evaporation occurs faster in the winter and regardless if that is true or not, the need to prime and for how long I believe is related to how much fuel is in the carburetor fuel bowl to start with, sometimes more sometimes less, all depends and the longer you go without starting, the more likely it would be to have less fuel in the carb which relates to more prime time. Not too mention of course, as the reason cobia6620 replaced his fuel pump, a weak pump certainly would take longer to prime than a new strong fuel pump. ~Craig
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Old 04-23-2021, 02:52 PM   #17
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Go to your generators and push the stop button. That first 5 seconds is STOP.

If you hold it for longer then 5 seconds, it goes into prime mode. Have someone listen to the generator and they will hear the fuel pump running, tick, tick, tick.

Once the carb bowl is full,the pump stops ticking, because its pumping against a shut needle valve.

You guys can go back and forth with the books, but that's how it works on my Generac 5500 AND our Onan Microlite 4000s.

Cranking the engine repeatedly for 15 second intervals is a starter killer.
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Old 04-23-2021, 03:36 PM   #18
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OK, I'mma gonna bow out as I don't have a Q4000, I also have the 5500.
Here is the owner manual that I was referencing. Scroll down to page 1-4 and it describes it and the start/prime procedure it after that.


Cummins Onan RV QG4000 Generator Manual
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Old 04-23-2021, 03:51 PM   #19
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Quote:
Originally Posted by twinboat View Post
Go to your generators and push the stop button. That first 5 seconds is STOP.

If you hold it for longer then 5 seconds, it goes into prime mode. Have someone listen to the generator and they will hear the fuel pump running, tick, tick, tick.

Once the carb bowl is full,the pump stops ticking, because its pumping against a shut needle valve.

You guys can go back and forth with the books, but that's how it works on my Generac 5500 AND our Onan Microlite 4000s.

Cranking the engine repeatedly for 15 second intervals is a starter killer.

I certainly agree, I stated 3 seconds of the stop button but it could have been 5, so 3~5 seconds, and another thought as I had edited one of my replies earlier, the fuel pump on mine makes a clicking sound (likely they all do) which makes me think perhaps the pump doesn't have a rotating motor, maybe it has a solenoid plunger type of pump (not sure what they would call it).

Anyway, I will add a thought, while I don't know if all the Onan's have a primer option or not, I would highly consider making a simple mod if mine didn't have a remote primer and that would be to install a momentary switch next to the remote start switch so I could momentarily turn on the fuel pump for 15~30 seconds prior to trying to start the generator if it hasn't ran in a while. As TwinBoat mentioned, running the starter over and over unnecessarily and for an extended duration each time is a starter killer, and one that could be avoided. I never run my starter for more than 5 seconds anymore, because running it longer than that isn't needed.
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Old 04-23-2021, 04:03 PM   #20
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Quote:
Originally Posted by F4Gary View Post
OK, I'mma gonna bow out as I don't have a Q4000, I also have the 5500.
Here is the owner manual that I was referencing. Scroll down to page 1-4 and it describes it and the start/prime procedure it after that.


Cummins Onan RV QG4000 Generator Manual
It is all good, and I hope no one ever gets offended with this type of discussion as for sure offending anyone is not and would never be my intention and I know there was a time (years back shortly after I purchased mine) that I didn't know about the prime function until a fellow RV'r told me about it and suggested for me to try holding the stop button down for ~15 seconds and see and sure enough... I also didn't know I didn't have to hold down the stop button to shut off the generator, just a simple one second quick push. I will add that even though the manual you shared doesn't reference a prime function on the remote, that mine and as others like the person who told me about it many years back do have that ability, in fact you can purchase a replacement remote that has the word "prime" on it although it certainly could be the case that the generator has to support that ability. Thanks, Craig
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Old 04-24-2021, 05:23 AM   #21
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thanks to all for all the good info
I do have Q4000 Model KY Spec L and have found generator parts plus operator and service manuals for this generator online.

I have thee start stations--- in the cab, near the rv door and on the generator. The hour meter is located by the rv door. All three switches will prime the pump if the switch is held in the stop position for a few seconds. Using the one in the cab with the door open allows me to hear the fuel pump run as the generator is below and behind the cab.


this is in the rv manual:

Generator Operations
To start the generator:
1. Press generator remote switch until generator
is running.
2. To stop the unit, press switch and release.
If the generator is slow to start, DO NOT hold
the switch in the START position for more than
10 seconds. Release the switch, wait 15 seconds,
then try to start again. This will help avoid
overheating and damage to the generator starting
system.

The generator operator manual is attached

I agree trying the starter every 15 seconds is bad and will switch to 30 seconds. With the new pump I should only have to prime once. If I don't prime it will not start after sitting 30 days. I never hold start button for 10 seconds-- 3-5 at most

I'm a retired engineer, grew up on a farm, and am no stranger to gasoline engines. When I was young we did not have computers and had to learn on our own which was rough and painful. Today the information available is unbelievable.

What is frustrating is not being able to obtain accurate manuals, elec diagrams and schematics for my rv. I've contacted Fleetwood numerous times and they have sent me all they have which are generic and often not accurate. So I've created my own and due to no rv certified tech being close I have to do all my own maintenance and troubleshooting.

The info I've obtained from the forum is priceless. I always believe that what ever problem I encounter someone else has had it before- so why not learn from others.
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Old 04-24-2021, 11:25 PM   #22
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Quote:
Originally Posted by F4Gary View Post
In looking in the Q4000 Owners Manual pdf it appears it can only be primed with the switch that in on the genny and not the switch mounted inside the coach.

The Control Switch is labeled Start and Stop/Prime and has the little yellow light. The switch on the dash does not.
Maybe on some rigs. On ours, I prime the Microlite 4000 by pushing and holding the "stop" button inside the rig. The hour meter will display a symbol and I can hear the pump run.

If I think the genset needs priming, I hold the stop button in for a few seconds, release, then hit the start button to crank the genset.
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Old 04-25-2021, 01:22 AM   #23
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Gasoline evaporates from the carburator bowl in 2 to 3 weeks, so its basicly out of gas.
That's why you prime it.
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Old 04-26-2021, 12:37 AM   #24
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My 22-yo Emerald Plus (BGE/4kw) has no codes/ no prime function, and 3-yo fuel pump, I typically crank 3-seconds, pause 3-seconds; repeat, will generally start by 3rd crank, (occasionaly 4th) even if not started in 2-3 weeks.
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Old 04-26-2021, 09:45 AM   #25
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Quote:
Originally Posted by THenne1713 View Post
My 22-yo Emerald Plus (BGE/4kw) has no codes/ no prime function, and 3-yo fuel pump, I typically crank 3-seconds, pause 3-seconds; repeat, will generally start by 3rd crank, (occasionaly 4th) even if not started in 2-3 weeks.
Holding the start button in energizes both the pump and the starter motor. The carburetor will fill with fuel during cranking but it could take several seconds. I figure that being able to prime first, via the stop button, simply helps to save the starter motor from excess use (heat build up).
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Old 04-29-2021, 09:04 PM   #26
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This is perhaps the greatest discovery for me in years of forum reading. Each month, to exercise the unit, I used to need to crank the generator for at least 30 seconds to get it to fire up. Would push for 15 seconds, let it wait for 15 seconds, then toggle it again. Sometimes took 3 cycles to get it to start. Now with the priming learned, it usually starts up in just a couple seconds. I hated to crank it so much, but thought that was just the way it was. Sometimes I am starting the generator when boondocking, and often the batteries are kinda low, so long cranking was not optimal. So happy now...
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Old 04-30-2021, 10:18 AM   #27
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This discussion has me scratching my head a bit: In our MH with the generator not running, pushing the generator rocker-type switch to it's STOP position causes the Onan generator's fuel pump to run - we can hear it's low muffled pulsating sound - so we know that the generator priming function is happening and just let up on the rocker switch to stop the priming after a few seconds.

To start the generator we just push the rocker switch the other way to it's RUN position momentarily one, two, or three brief times - as required - so as to fire up the generator.

It's all very simple ... I guess maybe because we can actually hear the Onan's fuel pump running for the priming function before we start it?
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Old 04-30-2021, 10:32 AM   #28
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Yes, all very simple. I did read somewhere that not all generators have this "primer" function but for sure most do. I will add that the fuel pump will stop pumping anyway once the carburetor is full of fuel. So you may want to hold the primer down longer until you hear the pump stop "clicking" as there is no harm in doing so, and that will result in a faster start time than holding it only for a few seconds (assuming the carb wasn't still full of fuel after a few seconds of prime). Also as a quick note, this type of primer is not what some of us old timers consider a "prime", in other words holding the primer down for more time than needed will not flood the engine with fuel compared to a bulb type of primer (such as on small engines) that actually push (squirt) fuel into the engine's intake. ~Craig
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