Genset "bangs" at startup and shutdown?

RanchoVectra · 07-03-2006, 03:41 AM

I tried the search function, but couldn't see that the question has been asked or answered: does your genset audibly "bang" when you start it up or shut it down? Mine does, to the point it just doesn't seem like it's good for the unit. It's an Onan on an 05 Vectra, about 150 hours, and so far as I know has had regular maintenence. I checked the fluids yesterday, and oil/coolant were at spec.

Does your unit bang as well?

RanchoVectra · 07-03-2006, 03:41 AM

I tried the search function, but couldn't see that the question has been asked or answered: does your genset audibly "bang" when you start it up or shut it down? Mine does, to the point it just doesn't seem like it's good for the unit. It's an Onan on an 05 Vectra, about 150 hours, and so far as I know has had regular maintenence. I checked the fluids yesterday, and oil/coolant were at spec.

Does your unit bang as well?

Kiwi · 07-03-2006, 04:29 AM

No bang for me. I have about 500 hours on genny and have never had a bang on startup or shut down. Mine is the 7.5Kw Onan that runs on the Kubota diesel.
Walt

RanchoVectra · 07-03-2006, 04:47 AM

Thanks, Walt. Didn't think it was normal despite what the salesman said when I picked it up last weekend. Don't normally have to use it, so will have them look at it when it goes in later this month.

SargeW · 07-03-2006, 05:40 AM

I think that is the first line that they teach them in salesman school "Oh, that's normal"

And the second one is "this baby will get (insert wild mpg here) miles per gallon".

John_Canfield · 07-03-2006, 06:18 AM

What exactly do you mean by a "bang?" Our generator has a very noticeable low frequency rumble/shudder when first starting or stopping which to me just sounds like the result of the ignition/starting process. It has always done this and it runs like a Swiss watch after two or three seconds.

Sarge is so correct...

I always assume a salesman will lie to me either because A) there is an intent to deceive or B) they don't know the answer and don't want to appear ignorant and finding the correct response isn't important because that has nothing to do with making the sale.

abarkl · 07-03-2006, 06:22 AM

Mine exhibits the same sort of "bang" on shutdown. I've recently checked the mounting bolts but perhaps it needs to have the shock mounts replaced. Mine is a 2001.

smlranger · 07-03-2006, 06:23 AM

You can always tell when a salesman is lying to you....whenever his lips are moving

Rich Bock · 07-03-2006, 07:54 AM

I get a "bang" also. In this case I really do think it is "normal".

rebelsbeach · 07-03-2006, 08:46 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by smlranger:
You can always tell when a salesman is lying to you....whenever his lips are moving

</div></BLOCKQUOTE>

While that's certainly a "time-worn" phrase, it's not always true....

Regrettably, there are "bad apples" in every line of work,whether it's RV or real estate sales or even health care management...

Thankfully, I truly believe I've found a salesperson that has not only the DEALERSHIP's best interest at heart, but the best interest of the customer as well.
In my last experience, while the service manager and his department were really good, I became disenchanted with the treatment I received from the salesman....

Gary, I believe in his case he fit your analogy....

Gary RVRoamer · 07-03-2006, 10:35 AM

It's not unusual for a genset to kind of shuuder as it starts up or shuts down. My guess is that your "bang" is either a fuel line or exhaust pipe getting stressed or de-stressed during that moment of shudder/vibration. Maybe thhe exhaust pipe hits a support as it moves a bit?

Can you have someone else start the genset while you watch & listen closely?

rebelsbeach · 07-03-2006, 11:56 AM

The 7.5 Onan in my Vectra shudders as you describe from time to time...Has always worked great!!

LouRobin · 07-03-2006, 01:01 PM

I think my shudder could be include a "bang"
It's a 7500 Onan Diesel

Sweet40FD · 07-03-2006, 02:06 PM

I have the 7500 and it also shudders. But works great.

gunny · 07-03-2006, 04:10 PM

Model and spec of the generator?

CJBROWN · 07-05-2006, 09:32 AM

I had the same issue with mine when it was new, salesman said "that's normal". BS, it's not normal for them to bang.

I started and stopped the genset while sitting there in front of it. It jumped all over the place because all of the mounting bolts were loose.

Also, the fuel line was routed incorrectly, and it had a sharp bend in it that surely would have kinked the line at some point. I re-routed the line to through the access hole provided in the framing.

I also shortened the virtical length of the exhaust pipe so it hugs the valence at the rear with about a 1/2" of clearance. Then I cut off the pipe at an angle so it only sticks out about an inch and a half.

It was a much cleaner installation when I got done with it and now works perfectly.

Don't forget to change the oil in the first 25 hours of operation.

--Chris Brown

RanchoVectra · 07-08-2006, 08:48 AM

Thanks to EVERYBODY who replied, and my apologies for being so tardy in following up - work always gets in the way.

Anyway, John it is definitely a "bang" and not a shudder, but I haven't yet gotten around to having the wife start it while I sit outside in front of it. It's the standard Onan Diesel 7500, and from what I am reading the bang isn't normal. If I don't find anything from the visual on start up the next stop is the Cummins shop in Irvine, not too far away.

Thanks again for all the replies.

jimandsue60 · 07-08-2006, 10:33 AM

Mine also has a big shudder when it starts, slightly smaller when it shuts down. Our cat (feline) jumps about a foot in the air when she is sitting on the dash and I start the genset. I will check for loose fastners.

Jim

gunny · 07-08-2006, 10:40 AM

No such thing as a "standard" Onan diesel.

If you could supply us with model and spec number, we would know exactly what you have and some of us who happen to work on them might just know of any known issues.

Model and spec numbers are on the decal on the generator.

A diesel will "shudder" when first starting or when coming to a stop. If the mounts are loose, missing or broken one of the components may be getting banged against something else. Not good. You may have something else loose that is getting rattled at start/stop.

A bang such as a backfire is something else. Pretty unusual for a diesel to have that happen but not unknown.

'05 machine. Is it under warranty? If so, guess what I'd do. Yup, off to the dealer before the warranty runs out. Cummins is usually pretty good with their warranty, 2 years I believe.

Let us know what you find.

skitime · 07-08-2006, 11:51 AM

I have had this bang. I was a muffler clamp hitting the frame. I was easy to find. With the generator off just shake the generator in its mounts in all directions till you find what is banging and I don't mean a gentle shake.