Onan MicroQuiet 4000 crapped out while running

[emcee]

Check out my 4KY generator grounding issue here: Solenoid fast clicking and generator won't turn over - iRV2 Forums

 

[DonTom]

Check out my 4KY generator grounding issue here: Solenoid fast clicking and generator won't turn over - iRV2 Forums

Different than my problem. But I will post a picture in a little while.

I have my generator working perfectly now, all fixed, I just need to make a few minor adjustments and such for frequency under load an no load. I discovered a missing c-clip behind the adjustment screw making it impossible to adjust. I just now purchased a new C clip and the local hardware store and about to install it.

I have already ran the generator for a full hour today.

I wonder how long I can safely run it with no cover at all.

It's cool today, so that helps.

-Don- Auburn, CA

 

[DonTom]

In the left photo below, look at just below the two control board screws. Then look at the bottom plate. The engine ground wire goes to the the bottom plate (just below the screws). The RV ground wire does go to the same plate as those two control board screws. Two different areas.

The side with the two screws does NOT make electrical contact with the bottom plate, but should. The bottom plate makes good connection to the engine. But that bottom plate does NOT see the ground from the plate with the screws, yet it looks almost impossible to happen for the bottom plate not to ground anywhere around the entire frame, goes to the ungrounded engine only. But that is exactly what is happening.

IOW, the engine is not getting any ground being only connected electrically to the bottom plate by that braid cable.

The right photo show the fix, at least for now. Side plate is now grounded at the RV cable ground trough my added cable. Without my added cable, now, not even the fuel pump will run. At first, it was only the starter. Now there is more resistance between the side plate and the bottom plate and nothing can run using the bottom plate of the generator as a ground.


BTW, I have my generator now running perfectly and on frequency and all. I am just waiting for a couple of maintenance items to come in the mail before reinstalling the generator. I ran it for around an hour two times today from a could start. I ran it with no load (other than converter) up to 2,400 watts (electric heaters).

-Don- Auburn, CA

 

[DonTom]

I don't think mine has a hose to nowhere, but I will check this afternoon and let you know. As to the breather hose here is a link to the ebay seller where I bought mine a couple of years ago, it looks like the price has went up a couple of dollars since I bought mine, Genuine - Onan Cummins | 123-1917 | RV Generator Breather Tube Micro Quiet KY | eBay

I replaced the breather hose today and I also figured out the "hose to nowhere".

I purchased to Onan parts book for my generator.

The "hose to nowhere" in front now goes to the fan. It's a Onan 503-1351.

I don't know how long it's been over the engine as my photo shows, perhaps that happened when I removed the generator or perhaps it has been that way for years.

But I discovered today there is a place for that hose behind the blower (parts book term for the fan). There is a hole in the rear of the fan for that hose. The front part of the hose fits in there perfectly. I don't know why my parts book calls that hose a "preheater hose" as I cannot make any sense out of that. What it does is blow the air from the blower to the back lower area of the engine.

BTW, I now have the generator reinstalled in my RV. I started the job late today. Rained all day yesterday. I still have to connect all the wires, connector and fuel line. But I expect the job to be 100% complete sometime tomorrow.

-Don- Auburn, CA

 

[udidwht]

The Onan 4K is supposed to have a ground cable from the outer (exterior) corner of the generator near front. That cable runs to the RV frame. Page 1-2 shows it's location.

https://www.cummins.com/sites/default/files/rv-manuals/0981-0607.pdf

Also view pages 8-7 thru 8-13...

https://manuals.heartlandowners.org/manuals/Electrical/Generator/Onan%204000/ONAN-Microlite%204000%20Service%20Manual%20Spec%20K.pdf

 

[DonTom]

The Onan 4K is supposed to have a ground cable from the outer (exterior) corner of the generator near front. That cable runs to the RV frame. Page 1-2 shows it's location.

Yep, but mine has a weird grounding problem. It has no continuity at the plates between the many screws. Didn't seem possible but my ohmmeter proved it. So did the DC voltage from ground to ground. The external ground cables were fine. So was the one internal grounding strap.

The starter didn't have a return path so it wouldn't crank, making me think I had a starter issue at first.

The problem first showed up while I was working on the genny, changing the carb, which I wouldn't think would be related.

See the two screws in message 83 in the left photo? Between all those screws and the bottom plate was infinite resistance. The fix also proved it, by running a new ground cable to the genny shown in the right photo. Then it cranked just fine. The stock ground cable to the genny side didn't make it to the bottom plate and genny engine where the alternator and genny engine ground was.

It's been more than a year since I did all that, but that is the way I remember it all.

-Don- Reno, NV

 

[udidwht]

Where the ground connects at the corner (exterior) of the generator it will need the braided ground strap on the inside connected from the generator base (metal) to the engine for complete path. The engine sits on rubber mounts. That will eliminate you having to run a ground cable thru the cover the way you have it.

 

[DonTom]

braided ground strap on the inside connected from the generator base (metal) to the engine for complete path

That was the first thing I checked and it has nothing to do with my issue. Where I had no connection ended up being on the plate that is screwed to the other plate on the side. Infinite resistance between those same plates. I assume corroded threads on the screws as where as corrosion where the plates touch. Didn't seem possible . . . but . . . my meter was telling the truth.

See left photo, message number 83. Those screws shown had infinite resistance to the touching bottom plate. I do not now recall why the bottom plate was important to complete a path. Notice that was an old message.

-Don- Reno, NV

 

[udidwht]

The bottom plate is important due to it being where the ground cable connects to from the chassis frame to generator corner. A ground cable from inside then connects from lower generator frame to engine (separate cable). I'm betting the cable that went from generator to chassis frame is built up with corrosion inside sheathing effectively making it moot.