Genset surge

Topic: Genset surge (Read 1591 times) previous topic - next topic

Genset surge

July 26, 2017, 12:39:04 am

Onan Emerald 3 6.5 kw lpg is surging +/-20v untill nearly fully loaded, after extremely rough road trip will check plugs, points and wires, air filter looks good. Oil ok. Any other suspects?There is a thread about rear bearing, about to order service parts? May be a weak cylinder?

Re: Genset surge

Reply #1 – July 26, 2017, 10:40:58 am

Is this a liquid lp generator or vapor lp generator (look on the lp tank to see if there is a liquid tap for the generator)?

Re: Genset surge

Reply #2 – July 26, 2017, 11:11:23 am

When you say rough trip do you mean a few things went bad or the drive was off road?

Off road could be a wire wiggled loose.

Re: Genset surge

Reply #3 – July 26, 2017, 12:02:26 pm

Quote from: DavidS – July 26, 2017, 11:11:23 am

When you say rough trip do you mean a few things went bad or the drive was off road?

Off road could be a wire wiggled loose.

Eastbound I-40 out of Barstow, potcraters 100' on center. Lots of things giggled loose and required stops to fix. Ditch may have been smoother. Did a walk around about every 90 minutes to survey rig.

Brett will double check but I think it's vapor, has a regulator with rubber vent hose, which I will check for critters.

Re: Genset surge

Reply #4 – July 29, 2017, 11:22:14 pm

Vapor generator, I can see the carb butterfly cycling, is there a way to dampen the movement, or is something else going on? It appears there may be a possibility that this unit may slide out somewhat to allow service to the back cylinder. Is it supposed to slide out?

Re: Genset surge

Reply #5 – July 30, 2017, 12:15:32 pm

Phred
If it's anything like mine (6.5 onan) the gen-set does not slide out as there are 2 1/4 bolts tying the rails down. You can work on the rear cylinder but it's a back strain deal with the access door in the way

If you got the manuals with the coach the gen-set book shows how to adjust the gov/throttle so the surging is reduced, I'm at 5,000 ft so it acts up a little at sea level then settles down.

Re: Genset surge

Reply #6 – July 30, 2017, 07:35:19 pm

There is a sensitivity adjustment on the governor and also if it is to lean will cause it to surge.

Re: Genset surge

Reply #7 – July 30, 2017, 07:50:32 pm

Interesting-- at least in 1993, they were using LIQUID LP generators (easy to tell because there is a liquid tap on the LP tank).

There are some very well known issues with these. But if yours if vapor they would not apply.

Re: Genset surge

Reply #8 – August 04, 2017, 12:03:02 am

Ok, 3 manuals don't show adjustments for surging no reference to governor sensitivity adjustment, there appears to be a adjustable rod end on the governor linkage that may be able to shorten the stroke of movement somewhat. And the main jet adjustment screw. Fatten the fuel mixture first and check the one accessable spark plug for carbon? Can't find points or condenser to check. Must be on the backside next to ignition coil. May have to yank the whole thing out just to work on it.

Re: Genset surge

Reply #9 – August 04, 2017, 10:20:14 pm

There should be a screw on the carb body that if screwed in will increase engine speed sometimes you can run it very close to the stop and with less area to move might stop the surge. Which model of Onan do you have? I am not sure if it is an NH or a NHE. I should have service manuals for either one and I can check on governor adjustments. I think the spring tension on the throttle rod is what controls sensitivity.

Re: Genset surge

Reply #10 – August 07, 2017, 12:13:33 am

It's a NHE, accessable spark plug is very light tan almost white, so I may need to fatten the mixture a tad bit. There is a right angle knurled valve with a lock nut on that would appear to adjust/distribute propane in a radial fashion into the carb inlet just down stream of the air filter i was hesitant to attempt to adjust with it. There does not appear to be any modulation of the propane fuel anywhere. So do they modulate the combustion air via the butterfly? Tailpipe fatigued off the muffler on the extremley rough I-40 trip home, so I may be getting some recirculation of oxygen less exhaust air.

Re: Genset surge

Reply #11 – August 07, 2017, 12:18:08 am

No muffler less back pressure would run lean.

Re: Genset surge

Reply #12 – August 07, 2017, 12:13:32 pm

When you get all done, check your cycles to be on 60. Some of these adjustments may effect engine RPM.

Re: Genset surge

Reply #13 – August 07, 2017, 09:05:46 pm

The color of the spark plug sounds right for propane.

Re: Genset surge

Reply #14 – August 07, 2017, 09:39:03 pm

Was reading your original post. If generator has been operating normally and is suddenly erratic, I would check governor for either a sticky mechanism or an excessively worn mechanism. I wouldn't think the sensitivity adjustment wouldn't suddenly need adjusting that much, but would be the next step if mechanism is moving freely and is not overly worn. If that doesn't work, the next approach would be to replace the governor spring.

Re: Genset surge

Reply #15 – August 07, 2017, 10:22:11 pm

Quote from: sedelange – August 07, 2017, 09:39:03 pm

Was reading your original post. If generator has been operating normally and is suddenly erratic, I would check governor for either a sticky mechanism or an excessively worn mechanism. I wouldn't think the sensitivity adjustment wouldn't suddenly need adjusting that much, but would be the next step if mechanism is moving freely and is not overly worn. If that doesn't work, the next approach would be to replace the governor spring.

Maybe over freely after I went around the coach and cleaned off grit and sprayed dry Teflon lube on all, locksets, hinges, latches, and any moving parts that I could observe and get to. Maybe it relied on some friction. Upon further inspection a few minutes ago, the plastic rod end has a lot of play in it only to be multipled by a lever arm. May have add some grit back, and then order a new one;-)

Re: Genset surge

Reply #16 – August 07, 2017, 11:03:01 pm

Doubt it needs grit back but a loose rod end will definitely cause a problem. Looseness from wear is different than freedom of movement from being clean and lubricated.

Re: Genset surge

Reply #17 – August 07, 2017, 11:06:59 pm

Wow my old info brain is getting a workout.

I think the play in the governer rod does cause surging. If held tight I think the surging stops

Re: Genset surge

Reply #18 – August 08, 2017, 12:52:21 am

Bearings worn. Likely replaceable. Governors like smooth operation with tight clearances to provide dampening affect. Looked at parts manual. Rod end worn or a hole in arm being too big could be your problem.

Re: Genset surge

Reply #19 – August 08, 2017, 09:16:14 am

I believe I have found the sensitivity adjustment, you can alter governor spring tension via a Phillips head screw hidden under a lever arm. I will try racer stainless safety wire to tighten the clearance on the plastic rod end. After that I may fool with the fuel mixture, after putting a manometer on the gas regulator. I have never seen an engine until now with no fuel supply to the carburetor, which only serves to modulate air for combustion. Then again, mechanical diesels modulate fuel and wait the airflow to catch up.

Re: Genset surge

Reply #20 – September 06, 2017, 10:42:11 pm

I just discovered the OEM coach wiring to the ATS from the 6.5 kw genset is 12 guage, lots of voltage drop. No wonder when the front a/c kicked on genset, all hell would break loose and the genset would shake the whole coach and surge for about 10 minutes on the trip home thru Needles Ca. at 112 F. Front a/c unit finally died three weeks ago in 105 heat from surge abuse I assume. Hard start capacitors can only do so much.

Re: Genset surge

Reply #21 – May 13, 2019, 10:42:09 pm

While reading another post, it just hit me, thought it had to be play in the old linkage, never hooked up a manometer to see what the gas pressure was, because it's not listed in trouble shooting guide. This year it seems worse. hell it may be surging due to a regulator. Vapor regulator at generator is supposed to be per application manal -1/2 w.c. so I am guessing 30 year old rubber diagram, unhooked the vent hose to make sure critters hadn't built nest in there. No change. Will check "carb" and inlet connection as -1/2 w.c. isn't much. Seems like I heard somewhere that spiders or other insects are attracted to log oders

Re: Genset surge

Reply #22 – May 14, 2019, 08:43:09 am

Quote from: Old phart phred – May 13, 2019, 10:42:09 pm

While reading another post, it just hit me, thought it had to be play in the old linkage, never hooked up a manometer to see what the gas pressure was, because it's not listed in trouble shooting guide. This year it seems worse. hell it may be surging due to a regulator. Vapor regulator at generator is supposed to be per application manal -1/2 w.c. so I am guessing 30 year old rubber diagram, unhooked the vent hose to make sure critters hadn't built nest in there. No change. Will check "carb" and inlet connection as -1/2 w.c. isn't much. Seems like I heard somewhere that spiders or other insects are attracted to log oders

I know you answered this earlier, but, please VERIFY by looking at the propane tank. Does the propane tank have both a VAPOR port going to the house regulator AND a liquid port with a line going over to the generator? Or does the line to the generator come off the vapor port?

And, on the generator, is the regulator internal or external to the unit? Picture or make and model of the regulator if external would be very helpful.

Re: Genset surge

Reply #23 – May 14, 2019, 09:49:38 am

Repair the muffler before changing the jetting . Reduce the slack in the control rod if it looks out of range. IMHO.

Re: Genset surge

Reply #24 – May 14, 2019, 10:01:02 am

Also check the governor sensitivity adjustment. Sometimes if the low speed adjustment screw is run a little closer to the stop on the throttle shaft so that it doesn't have as much room to oscillate that can help with surging. Also if to lean will surge. If I remember right there should be 2 regulators at the tank if you have the vapor withdrawal for the generator.

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