Generator surging/searching

[chboone]

Originally Posted by Algoma

chboone, I can only assume you have never owned an Onan QD generator.

Doesn't matter diesel, gas, natural gas, propane or which manufacturer if the rpm's are fluctuating the frequency will follow. RPM'S = frequency. Voltage by voltage regulator, the lower the volts the higher the amps, the higher the volts the lower the amps, OHM'S law.

[Algoma]

[moderator edit]You appear to have a gas RV and presumably a gas generator. The Onan QD generator is a variable speed generator and the output is provided by a solid state inverter. This is not a synchronous generator (as is the Generac). [moderator edit]

[Koop]

Originally Posted by chboone

Doesn't matter diesel, gas, natural gas, propane or which manufacturer if the rpm's are fluctuating the frequency will follow. RPM'S = frequency. Voltage by voltage regulator, the lower the volts the higher the amps, the higher the volts the lower the amps, OHM'S law.

Well...this is what I thought before. My gasoline powered Onan 5.5Kw generator worked as you stated. My 7.5Kw Onan Quiet Diesel works differently. The RPMs vary while the output is constant. I don't understand the system at this point, but I'm researching. It's a fantastic generator!

[94-Newmar]

Chboone/Koop: As algoma mentions above, the QD7500s and above are inverter based generators. The RPM of the engine will vary from idle to 3525 rpm based upon the load/demand on the AC side. The QD5500's and below (with one exception) are conventional generators and will attempt to sustain a fixed rotor speed regardless of load.

Jerry: In the majority of cases with a QD hunting around at different RPMs unrelated to load you will find it's fuel delivery related. In the majority of those cases it is the fuel filter that is needing replacement, but it can be cracked fuel lines allowing air in the lines or a failing fuel pump. Cummins/Onan has a recommended fuel delivery test as follows:

FUEL PUMP/Fuel Flow Test

1. Disconnect the fuel return hose from the line to the supply tank and point the end into a quart (1 liter) or larger container that has volume graduations. There are 2 fuel lines entering the unit. 1 is the supply, 1 is the return line. Make sure all testing is done from the RETURN line which will be clearly marked on the cover.

2. Prime the genset by pushing the Start/Stop switch to STOP and holding it there for the duration of the test. Flow rate into your container should not be less than 200 ml (0.4 pints) per minute.

3. If flow is less than specified, replace the fuel filter. Re-test. If that does not help, look for other issues in the fuel system such as wet or leaking fuel lines especially at unions and connections. Last, replace the fuel pump as the pump is not serviceable.

If the unit passes the delivery test, I use a separate powered small 12V fuel pump and a 1 gallon container of fresh fuel. Using my own supply/return lines I'll run the unit on my "test" pump and fresh fuel to see if the problem still exists. If the problem clears up then I'll look at the 12v wiring to the pump and/or replacing the fuel pump.

[monsterdon]

I have just gone through the entire process of "solving" the surging/dying issue with my 7HGJAB Marquis gold Onan gasoline powered generator. Despite sucking in full strength carb cleaners with fuel pump and letting it sit for days - it still had serious surging issues. My carburetor had a black plastic altitude adjustment tab that limited the movement of the idle mixture screw. My generator appeared to be running quite lean (when it would run), because spraying ether, or manually closing the choke butterfly would keep it running.

When I removed the bowl, I noticed that the movement of the black plastic tab did not move the needle valve of the idle mixture screw. I removed the black plastic altitude adjustment tab by prying between the bowl of the carburetor and the tab with a flat screw driver, and noticed that the gear splines in the black plastic were stripped away. I then removed the brass idle mixture screw, cleaned off varnish remains and cleaned the port with spray carb cleaner and a bread twist tie wire. I reinstalled the idle mixture screw and started with tightening the screw all the way in (stop at light resistance - don't strip the screw) and then backed it off CCW 2 turns. Generator started, and after allowing it to warm up, I ended up at close to 3 turns before finding the sweet spot for highest RPMs and no surging (Sea Level).

I also noticed that surging could be achieved by both a rich mixture and a lean mixture. This explains the myriad of symptoms in the different threads of carb issues associated with 5.5 and 7.0 Onan gasoline generators. Some folks described symptoms of rich mixtures, others had symptoms of lean mixtures. It all depends where the idle mixture adjustment screw is stuck.

My RV is a 2007 Tiffin Allegro with a 7HGJAB Onan gasoline generator that now runs normal without the stripped black altitude adjustment tab and $250 dollars still in my wallet.

[Old Scout]

Interesting, OP is posting on the Alpine Forum but his sig-block suggests he now owns a 2017 Dutch Star 4018. So hard to know which coach he now owns but suspect either way, he has a diesel genset. Great conversation on diagnosing gas and propane gensets--just not applicable to this thread.....[smile]

[Jeff and Cheryl]

Just a little history here. Algoma had an Alpine for many years, a year or so ago replaced it with a new coach.

[DrDaveMA]

One of the pit falls of digging up old postings is that things change (particularly with WRV out of business), data can appear to not be relevant to this forum. In January 2014 when Jerry Davis did the original post he owned an 05 Alpine (he was the original owner). Since that time he has purchased a new coach (he is now a SOB, Some Other Brand) and his signature block reflects what he currently owns. Many folks like Jerry and Algoma have a wealth of Alpine specific knowledge, however it is impossible to know that from their current signature blocks. I fear that as our coaches age this will be an all too familiar story, maybe we need to create an Alpine alumni category, it would be a shame to loose the 10+ years of knowledge people like Jerry gained during their Alpine ownership.

[tiredvet]

Well said Dave, Jerry and Algoma have a lot of knowledge that has been so helpful with so many Alpine owners.I have learned so much from these two Experts.

[Bob_C]

Sure didn't see a padlock on this thread.....hummm.

[DrDaveMA]

Originally Posted by tiredvet

Well said Dave, Jerry and Algoma have a lot of knowledge that has been so helpful with so many Alpine owners.I have learned so much from these two Experts.

One of the things folks that don't know Alpines do, is they assume that WRV did things like other manufacturers do. As an owner we KNOW WRV did not do this and have to watch what is suggested by other brand owners, they can sometimes lead you down a rat hole. For example I am not aware of another coach that uses a Vansco bus, but as is the case for this thread, an Onan Quiet Diesel works pretty much the same if it is on an Alpine, Monaco or Country Coach.

There are several IRV2 members that know Alpines even if their signature shows that they have moved on to a newer coach. We want their knowledge and participation on this forum. We also appreciate the participation by other brand owners, but we, as Alpine owners have to recognize when we are getting advice that is contrary to how our coaches operate.

[jerry davis]

Even tho I now own a different brand of coach I truly loved my Alpine and will always think kindly of the great travels it gave me.

[Scarab0088]

Thread closed...old thread reopened after OP has changed RV's.

Thanks to all who posted within the Community Rules.

Steve as iRV2 Staff