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CHahn · 11-25-2022, 03:54 PM

I recently inherited a Class B+ camper. It's a 2003 and well maintained, but the generator was almost never used. But I want to use it for dry camping. Onan MicroQuiet 4000. On occasion I've been able to get it to start and run for about 2 seconds. I'm sure I have carb work to do, but first I need to troubleshoot the weak starting issue. It acts like it has a weak battery by sometimes turning over aggressively, and on the next try the starter does a partial turn and stops just like not having enough battery energy. House battery is in good shape. Engine starter battery in good shape. Tried with Engine running and same result. Tested with shore power connected, and same result. I disconnected large ground wire from starter solenoid to chassis ground and cleaned and reconnected. I tapped solenoid. No change. Any ideas?
In what I think is a separate issue, I disconnected the fuel at the carb to ensure the fuel pump was working. It does pump fuel when I prime it, and when I reconnect the fuel (and on the occasion when I can get the starter to turn over) it starts and runs a couple/few seconds and dies. This repeatedly happens when I disconnect the fuel, run a little out with primer, and reconnect. Otherwise it doesn't start at all.

Well, that's a lot to read and if you made it this far and have any ideas, I's appreciate your insight.

SteveJ. · 11-25-2022, 04:15 PM

I just replaced the starter on our spec G 4000 Microlite that displayed the same symptoms. I took the starter apart and discovered that one of the brush holders had worn away for some reason. One brush was just floating, cutting the power in half. A new Cummins branded starter from Walmart.com for about $110 cured that issue.

As far as the not running a sometimes it can be the shutoff valve inside the carburetor bowl is gacked up.

As an aside, as long as I was in there I relocated the fuel pump to the outside of the genny. As long as the genny was removed I also took the opportunity to mount the genny on rubber dampers. This greatly reduced the amount of noise inside the coach.

donr103 · 11-25-2022, 07:40 PM

Look on batteries and tell us.. how old each one is.. What are dates on batteries ? Sorry.. been thru this just too many times.. everyone says batteries are in great shape.. so.. unless you have a very expensive battery testers.. then drive rv to any good auto parts store and they will test for free.. that is 1st thing..
Good luck and keep us posted

MarvinG · 11-26-2022, 11:47 AM

Also, I long ago changed my generator battery connection to start from the chassis battery rather than from the coach batteries. Doesn’t make a lot of sense to try to pull starting current from the deep cycle batteries rather than from a battery designed to provide starting current. It made a world of difference. Consistently spins right over now.

CHahn · 11-27-2022, 11:02 AM

Thank you gentlemen. All sounds like good advice. I hope it's not the starter because I'd have to drop the whole thing from under the camper.

I was thinking exactly the same thing about starting the generator from a deep cycle battery and it would make more sense to use the starting battery on the chassis. But for now I'll stick to the original design and continue troubleshooting. My house battery is supposed to have 615 cranking amps which I think would be enough. If that's not enough, I hope someone here will let me know.

And, as they say, when you hear the sound of hooves, look for horses, not zebras. I'm going back to the house battery to ensure it's as good as I think. It's a Napa Marine/RV Deep Cycle, 500 CCA, 130 RC. Not too hard to remove and I already have it at my feet now. I'll take it to an auto parts store to be tested. Oh, date is 12/20.

Thanks again for all the advice. I'll check back in and let you know how it comes out.

GypsyR · 11-28-2022, 12:29 PM

Mine did that, or didn't crank at all. It had rust on the starter stud where the battery cable goes. I'd clean the heck out of it and the cable and it would be fine for about a year. Until about the third year when it wasn't. Acted just the same (like a weak battery) but it wasn't corrosion this time. I jumped the starter solenoid posts and it cranked. Solenoid clapped out internally apparently. New solenoid had better posts so hopefully the corrosion will no longer be an issue. Never had a ground issue, oddly enough. I "voltage drop tested" it a few times to confirm that.

CHahn · 11-29-2022, 05:46 PM

https://photos.app.goo.gl/FsEzQBQM9QdJJrqe9 Well, I have a new update. I did take the battery in to be tested and and the auto parts guy said it was bad. It didn't take a load as it should. So I got a new one, somewhat larger Marine/RV Deep Cycle, installed it and I have no changes. The generator still acts like it doesn't have enough power to turn over. But this time I tested it from the inside of the camper and noticed that there is a click on the solenoid inside the house battery compartment. I believe this is attached to the chassis battery. There is also another smaller device connected right next to it. What do these do and should there be a click (single click) when I try to start the generator?

donr103 · 11-29-2022, 08:57 PM

You are getting there.. now start chassis engine and after 5mins try generator.. make sure if you have disconnect switches by door that they are on.. they are momentary type.. so just push up.. you should here clicks of relay.. from what you describe.. next to house battery is BCC.. battery control center.. this unit controls batteries and charging of them.. there are old relays in there.. maybe some 12v fuses..
So imho. Start chassis engine.. let warm up.. keep running and try each switch for generator.. if still a problem.. do quick ground test as above..
You are working thru old system.. best one step at time.. you did have chassis engine battery tested correct ? If not.. you better.. because you can burn your chassis alternator up or worse.. free right..
Next look around in generator compartment and make sure you don't see a small starter battery just for generator.. sometimes in rare instances.. you will find one..
Most rv are wired to start generator off house battery.. sometimes they are changed.. report back and better opinions will follow
Good luck and keep us posted

CHahn · 11-30-2022, 04:49 PM

Thanks don3103. I've tried to start the gen with the cassis motor running before, but to no effect. Your advice of letting it run a while first seems to be the ticket. I still wish it would turn over from the house battery, but I guess it needs more cranking amps. Now on the carb. I think I know what to do there, just need the time to do it. Probably this weekend.

RealNiceTent · 11-30-2022, 05:33 PM

I have a little trick for you try with the carb. I don't know how good the access is to the carb, but if you can remove the fuel bowl, remove it and clean it out with carb cleaner(Berrymans is my preferred). While the bowl is off spray the dickens out of the bottom of the carb. Then before you put the bowl back on fill it as full of carb cleaner as you can and put it back on. With the ignition disabled after the bowl is back on and sealed crank the engine a little bit to finish filling the bowl and draw a little carb cleaner into the carb. Now just leave it sit a day or two, then if you can reach the bowl drain, drain the fuel out of the carb and after all the fuel has run out,stick the straw on the carb cleaner into the drain and rinse it out real good. Watch and see if a bunch of crap comes out of the carb bowl, and flush with the spray until it keeps coming out. then put it back together and try to run it.

I did this with a chipper shredder I bought that had been used once when the guy bought it, then it sat in his garage for about 15 years. When I pulled the bowl off it was full of fuel that had turned to gelled varnish. I've been using it for over a year with out much trouble.