Onan Microquiet 4000 generator runs 10-15 minutes than dies

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Onan Microquiet 4000 generator runs 10-15 minutes than dies

September 20, 2020, 04:53:07 pm

Hello, I have an Onan Microquiet 4000 generator in our 2002, 25 1/2 midbath. Recently the generator started a new issue where it will run for 10 to 15 minutes and then putter out.

I have scoured the internet, read forums, watched videos. I did search the site here, and didn't see a fix (although I could have missed it).

Here's what I have tried:
1. Tuneup - replaced spark plug, air filter, and oil. As per some recommendations floating around on the internet, I was careful not to overfill the oil.

2. Replaced the carburetor.

3. Disconnect fuel line, place it in a gas can. Hold down the start button, and confirm fuel flows. Also tried this right after the engine had puttered out - and there was still fuel flow.

If I wait a bit, maybe 20 minutes more or less, and try again, the generator starts up and runs without issue for another 10 to 15 minutes than dies again.

Has anyone else experienced this? If so, what was your fix?

BTW, the generator model # is:4KY FA26100J.

Sincerely,
Mike

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #1 – September 20, 2020, 05:12:21 pm

Did you pull a code? If not, the manual explains the procedure.

Steve

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #2 – September 20, 2020, 05:38:27 pm

Your LD has the classic symptom of rotted generator rubber fuel hoses. LDs of your vintage all suffer from this. LD used old fuel line for several years.
Our 2003 LD's lower generator hose started leaking two years after buying it. The upper fuel hose had to be replaced about four years ago when the generator completely stopped running.
The fuel lines develop small cracks that leak air. As the hoses continue to age, the cracks get bigger until too much air is pulled in, eliminating the flow of fuel.
It gets worse after the generator has run for a time due to the heat, from the generator, making the hoses temporarily softer, allowing the cracks to open up more, letting in more air. Some fuel may be pumped but not enough to maintain the increased fuel needs while under load.

The lower hose can be be easily located and changed.
Replacing the upper hose is more complicated. On some models, the gas tank can be partially lowered and, with long, flexible arms, the hose can be removed and replaced, other floorplans need the fuel tank completely dropped. With a rig as old as yours, if you need to replace the fuel line, consider changing the fuel pump at the same time,
The fuel pump is mounted inside the tank and can only be removed by dropping the tank. The fuel pumps have a history of going bad with time and mileage.
If you do, change the emission hoses, located on top fo the tank. Our emission hoses were also rotted.
Fuel tank generator hose replacement | Flickr
Fuel pump replacement | Flickr

To verify leaking fuel lines, have your mechanic run a temporary fuel line from the generator to a gas can and see if it runs for a long period, under a heavy load, such as the A/C or running a couple electric heaters.

There is a chance the fuel pump is failing.
This topic has been discussed in the past, search the archives for past postings.

Larry

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #3 – September 20, 2020, 05:41:25 pm

This may be of interest. In our ‘15 RB, we have the 4000 genny. Last week in Yellowstone our genny had been working fine although a bit rough at start up then run smoothly.

One day it would shut down shortly after starting. Being at nearly 8000 feet (judged by the Continental Divide signage) I decided to adjust the altitude screw. After that the generator operated flawlessly and smoothly.

That may be a good place to look.

Best of luck.

Kent

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #4 – September 20, 2020, 06:58:56 pm

Thanks for the info Larry. The fuel lines were replaced by the previous owner in 2013, and look to be in good shape. I am leaning towards the fuel pump.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #5 – September 20, 2020, 07:28:49 pm

Quote from: mikedad - September 20, 2020, 06:58:56 pm

Thanks for the info Larry. The fuel lines were replaced by the previous owner in 2013, and look to be in good shape. I am leaning towards the fuel pump.

Is it safe to assume you have more than ¼ tank full of gas?

Chris

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #6 – September 20, 2020, 07:34:35 pm

This video helped me change my Onan fuel pump this summer:
https://www.youtube.com/watch?v=gutZQAq5Trc&ab_channel=KATZFamilyadventures

If found a cheap fuel pressure tester to be helpful with troubleshooting. My pump would do fine (4psi, IIRC) most of the time but drop down to <2psi occasionally.

If you decide to change the fuel pump, change the fuel filter while you have everything apart.

A final possibility is that mice have chewed a hole in the plastic fuel hose on top of the tank. I speak from experience here.

Rich

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #7 – September 20, 2020, 08:00:09 pm

Check the oil level.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #8 – September 20, 2020, 08:24:11 pm

If the shutdown is due to a fault, the indicator will blink 3 or 4 times. Do you have a manual? Section 4 gives you the procedure for finding the fault codes.

Steve

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #9 – September 20, 2020, 09:22:43 pm

Fault code is 36.

ENGINE STOPPED FAULT—CODE NO. 36
(Engine stopped without command by controller)

Also, RV fuel tank is full.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #10 – September 21, 2020, 03:57:00 am

Quote from: mikedad - September 20, 2020, 09:22:43 pm

ENGINE STOPPED FAULT—CODE NO. 36
(Engine stopped without command by controller).

All Fault 36 indicates is the engine stopped, information you already knew.

When it is running, is it producing power? Have you checked the voltage with a voltmeter?
Does it stop running in the same amount of time when under heavy load compared to a light or no load?
When it stops running, does it sputter or surge before dying or does it stop instantly?
Sputtering would suggest a fuel issue, while stopping all at once points toward an ignition, wiring, or control board problem.

Larry

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #11 – September 21, 2020, 11:42:38 am

me exact problems your are having and I read numerous others too on the internet. i ONLY HAD 230 HRS ON
MY GNNY. NEW FUEL PUMP SOLVED PROBLEM!!!

I'll bet your new pump will solved your issue.

Bob Wilson

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #12 – September 21, 2020, 04:55:59 pm

Quote from: mikedad - September 20, 2020, 04:53:07 pm

3. Disconnect fuel line, place it in a gas can. Hold down the start button, and confirm fuel flows. Also tried this right after the engine had puttered out - and there was still fuel flow.

Not clear to me from this if you tried running the generator while the fuel line was still in the gas can. If NOT, then do so. If it now runs until you stop it or the can runs dry, then the fuel line IS the likely issue. Note you cannot see the fuel line on top of the tank without dropping the tank, and chances are the PO did not do that. The piece Larry shows in the pic is from that location, AFTER dropping the tank.

Steve

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #13 – September 21, 2020, 06:48:43 pm

Yes I ran the gen. with the fuel line in a gas can and it ran perfectly.   When fuel line was reconnected to the Rv's gas line
it would run for 15-20 minutes then quit.   there are numerous references to this exact set of circumstances on various
RV web sites. No one I talked to-including ONAN personnel could give an answer as to why the pump worked fine forr
these short runs then quit.   Many of the people who had the problem -put in a new pump reported on the nternet problem solved.

Good luck
Bob Wilson

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #14 – September 21, 2020, 07:29:52 pm

If, when you ran the gen from the gas can it was not gravity feed, i.e. the gas level was lower than the carb, then your pump is not the problem. The problem is absolutely the fuel line on top of the gas tank. It is short, rubber, and leaking air. This will also cause the gen to run lean, and therefore HOT. You need to drop the tank to replace the hose. You will find scores of rigs had the hose leading to the gen fuel filter replaced, since that is easily accessible. Unfortunately, the one above the tank continues to rot away...

Steve

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #15 – September 21, 2020, 08:30:32 pm

"You will find scores of rigs had the hose leading to the gen fuel filter replaced,..."

When the short rubber fuel line at the top of my tank went south I not only had it replaced but also had the plastic fuel line replaced with Stainless Steel.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #16 – September 21, 2020, 10:57:44 pm

"I not only had it replaced but also had the plastic fuel line replaced with Stainless Steel."

Ditto. I felt a lot better after that was done.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #17 – September 22, 2020, 12:24:37 pm

Could be either the fuel line or the generator's fuel pump.
On our 07 MidBath the problem turned out to be the generator's fuel pump. It would get warm after 5-10 minutes and quit. Changing the pump is not that hard but a multi step process that will take a while. I had to remove the air cleaner and several electronic components. But it comes apart with simple tools, mainly a ratchet, sockets, socket extension (a wobbler extension is nice), and wrenches. Bring a cell phone with a camera and every time you remove a nut, bolt or wire take a picture. This is important because as you get deeper all the wires are white. Most have specific ends, but there are a few head scratchers.

The Lazy Daze Companion: Generator

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #18 – September 22, 2020, 05:18:14 pm

Quote from: Jota - September 20, 2020, 08:00:09 pm

Check the oil level.

Earlier this year my gen set was shutting down after 5 minutes. Somebody here posted a link to a Youtube video about the oil level being too high due to faulty dipstick level markings. Anyway, I took a $2.00 turkey baster a removed some oil until it was to the add mark and it worked like a charm. It's been running great since.

https://youtu.be/vzXDlln8aUw

Hope this helps. Ron

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #19 – September 23, 2020, 06:51:25 pm

I had been having the same problem with my Onan Microquiet 4000 generator; it would run about 15 minutes and then die. After getting an oil change, changing out the fuel filter, even removing a little of the oil, it still had the same problem.

I ordered in a fuel pump, which arrived here last week. Today my honey/electrician/all-around handy guy removed the old fuel pump and installed the new one. I'm happy to report that the generator now runs fine.

So another vote in the fuel pump column as something to try if you have this same problem.

I will say that it was a real PAIN to work in the cramped generator, difficult to remove all the parts that you have to get out of the way (lots of wiring bundles, the solenoid, and the board). Getting things back in their proper places was even more of a pain. As much as I like working on my own rig, I now realize that this particular job isn't something I should have attempted on my own.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #20 – September 24, 2020, 09:15:55 am

After you have replaced the fuel pump, filter, etc and it still does not work, I predict it will be the control board.
I had this problem and over a period of months, it would run shorter and shorter periods until it would start and immediately shut down. I thought I had written my experience up for The Companion. I recall taking pictures, but I did not find a post and at this distance, I can not recall the details.

The control board is a PIA to remove and put back. I elected to have a Cummins dealer do it for me. I got out for only $800 parts and labor. Only.

Take a peek at the board. You can see the circuits through the clear cover. If you see any brown areas, that's your problem. Maybe you can see it on a Microquiet. We have a 2007 and I think it's called something else.

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #21 – September 24, 2020, 01:14:16 pm

Without a full, in-person troubleshooting session by a qualified tech, we are all guessing about the cause.
It could be a leaking fuel line, a bad fuel pump, a bad control board or possibly some other cause.
The fuel line, fuel pump and control board are all common sources of this problem we have seen in past years on the forum and I had seen in my previous career. I have also seen failing generator armatures do the same thing in a few cases.

There are two ways of solving this, actually determining the cause or start throwing parts at it until something sticks.
Unfortunately, the control board needs a specialized tester, something only Onan or a good generator shop would have.
If the control board senses an electrical problem, it will shut the engine down. Code 36 is a possible indication of this happening.
This gives you a good view of what mechanics go through every day, what appears to be a simple problem many times turn out to be much more complicated.

If I had the same issue, I would first verify that the fuel line was not leaking.
If intact, not having a way to test the control board at home, I would probably replace the fuel pump with a genuine Onan pump and filter, the market is loaded with cheap knock-offs, and hope I had made the right guess. Onan shop repairs can get very expensive quickly.
If the stalling is still present, then it's time to visit an Onan repair shop, make sure to bring a good size roll of cash.

Larry

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #22 – September 25, 2020, 10:27:55 am

Quote from: Larry W - September 24, 2020, 01:14:16 pm

There are two ways of solving this, actually determining the cause or start throwing parts at it until something sticks.

I completely agree with everything Larry says about this dichotomy. I've been a parts changer, and I've been a troubleshooter.

These days, I find that my strategy has evolved to limit labor and hassle instead of limiting the cost of parts.

If I have to take something apart to troubleshoot it, and it's a part that tends to wear out (like a fuel pump or a fuel filter), I'm going to replace it so I don't have to take it apart again in a couple of years at a time that's probably more inconvenient.

If I have something apart, and it looks like it's starting to wear, I find myself thinking - do I really want to take this apart again? I only do this when I'm 'in there' anyway. I don't go looking for problems where there are none.

So I toss in a few more parts than I used to, and I don't feel bad if it doesn't fix the immediate problem as long as I think I could have prevented a problem for future me. Every so often it does backfire and I cause a problem by installing the replacement part incorrectly.

A few years ago, I would take something apart 4-5 times and milk it along just to save on parts because my labor is free to me.

Amazon probably has something to do with this. It's never been easier to get parts.

I'll leave it to the reader to decide if I've become smarter or just lazier over the years.

Rich

Re: Onan Microquiet 4000 generator runs 10-15 minutes than dies

Reply #23 – October 03, 2020, 07:32:05 pm

Solved!
I replaced the fuel pump this morning and the generator is running great now. Thanks for all of the information everyone.

-Mike

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