Upgrading Onan 4000

[eccentricson]

Originally Posted by paulwadley

Those could be the spark arrestor clean out plugs as per the diagram from the onan manual.

Paul

That's a bummer, I guess I overlooked it. Thinking the rubber gaskets were meant to help absorb some of the vibration....

[EA37TS]

When swapping generators make sure the compartment has the size necessary to allow adequate clearance for cooling. Some generator installations, with the required clearance, already suffer from over heating. Taking as little as an inch or less from the clearance could mean the difference between an adequately cooled generator ad one that shuts down from overheating every 15 or 20 minutes.

[eccentricson]

Originally Posted by EA37TS

When swapping generators make sure the compartment has the size necessary to allow adequate clearance for cooling. Some generator installations, with the required clearance, already suffer from over heating. Taking as little as an inch or less from the clearance could mean the difference between an adequately cooled generator ad one that shuts down from overheating every 15 or 20 minutes.

That's a great point. I think I'm at the next stage of my mindset, rather than throw money at it and replace the generator, fix the vibration and rough start. Just need to figure out what mount points are causing it to shake the entire coach when it turns off.

[Long & Winding road]

Originally Posted by paulwadley

Those could be the spark arrestor clean out plugs as per the diagram from the onan manual.

Paul

No, that would be on the muffler somewhere.

[Long & Winding road]

Originally Posted by eccentricson

So I checked out the bottom of the generator and tightening all of the screws to help with the vibrating of the coach when the Genny turns off. This star-bit bolt has a large rubber grommet with a washer. Looks to be used to absorb some of the vibration given the grommet. There are two of these bolts, and they're screwed all of the way in. But the grommet isn't even absorbing anything and isn't touching anything. It just spins. What part is this? I looked through the underfloor kit parts, I looked through the generator parts manual, but I can't find it. I worry the folks I purchased the RV from put this part in here and it doesn't belong.

As long as they are in place I think your fine. Grab the generator with both hands and shake it around some (with it off and not hot to the touch). It will shake around a lot but as long as it feels like its attached good and no clanging your fine. You can turn the Genny on and off right there at the Genny itself.

Do that and watch and listen. It will also prime it if you press off and hold in for like 30 / 45 seconds.

YOu can also see the breaker in that area for future refernce (my tripped once.... My AC was not working - easy fix).

[paulwadley]

The Onan manual for that generator shows those two plugs and says they are for cleaning the spark arrester. On my Onan diesel generator, my spark arrester plug is on the muffler but each generator is different.

Paul

[Long & Winding road]

Originally Posted by paulwadley

The Onan manual for that generator shows those two plugs and says they are for cleaning the spark arrester. On my Onan diesel generator, my spark arrester plug is on the muffler but each generator is different.

Paul

Ok, need to look into that. Very strange.

[Bob Denman]

Paul,
Now you're gonna make me crack open the generator bay on my rig, and take a look at that little "oil-burner"!

[aa0ri]

The 1st picture and the enlarged one show a large headed bolt with a rubber washer or something like a motor mount that looks like half is missing. I think that's the star head bolt he is talking about. If that's one of the motor mounts it obviously should be replaced, it in itself would cause the generator to shake on start, stop and under load. The tune up and oil change suggestions should be started just so you know where you are with it


Good luck finding the problem, I think that may be it.

[71_340]

If I were you I replace the rubber mounts for the generator as they are probably collapsed. That will take care of you shaking problem and isn't very expensive.

[Glensouth]

It would be an easy upgrade to the larger gen. As far as upgrading to 50 amps, very expensive and not worth it.

[ducksface]

Those appear to be, and you can verify, vibration dampers/motor Mounts. Mine are just as loose. The engine sits on rubber bushings/dampers on top of that plate. Being tight would restrict movement, but I'm not sure it would do much else. The engine is gravity mounted. It moves when you shake it, just as it should.
The slop could be purposeful to alleviate stress and allow the movement so castings don't crack under torque. Less tight the motor moint on any Gas engine is, the less likelyhood of cracking a casting. The rubber Mounts in your car aren't only about comfort.

I'm not worried about mine. They show no signs of shrinkage, warpage or wear. At 400hrs they look just like yours.

Preliminary measurements show a 5500 will fit where my 4000 is.
A simple electric fan will resolve any air flow concerns.
50 amp can be as simple with the generator as one extra line and required line goodies ran to added appliances. Add a 50 amp pedastal input plug if you insist on having one or just the 30/20 scheme with two plug-ins.

The Vega was designed for the small block but the monza was already approved as a draft, so no v8 Vega made production(and GM needed a pinto rival not a maverick rival).

Mom had a 4cyl Vega with ps/automatic and ac.
I had a 327 power glide spitfire.
2bbl 327 was 210 crank hp new, as it's best effort.

[Chance]

Originally Posted by eccentricson

That's a great point. I think I'm at the next stage of my mindset, rather than throw money at it and replace the generator, fix the vibration and rough start. Just need to figure out what mount points are causing it to shake the entire coach when it turns off.

In my opinion it’s smart to accept 4,000-Watt generator. Going larger to 5,500 will cost a lot, creates additional problems, adds weight, and consumes more fuel when running at lower percentage of rated power/capacity. It’s not worth it unless you add a second air conditioner and upgrade to 50-Amp electrical. Designers of some of the newest motorhomes seem to be trying to get rid of generators, so this 4000-to-5500 upgrade is a step backwards in my view.


My opinion on vibration as generator turns off is that much of it is normal. If you haven’t experienced this before, it may seem excessive, but perhaps it’s only your personal perception and expectation that it should be smoother. You may want to check other Onan 4,000-Watt generators.

The 4,000-Watt Onan engine is single cylinder and runs at 3,600 RPM, so it vibrates quite a bit. It’s normal to have vibration isolators (they’re not technically dampers) that allow engine to shake without transferring as much vibration to the motorhome. Problem is that if the isolators are tuned for 3,600 RPM (the speed the generator runs most of the time) they will not be ideal at low engine speeds as it coast down on shut-down.

Having said that, I’d check the isolators anyway to make sure they are good, but expect that with less than 1,000 hours they should be fine. If the vibration you’re experiencing last for more than a second or two, I’d question if your generator engine is running on instead of shutting off quickly as it should.

[DLM1965]

We recently changed our 2017 Thor Quantum PD31 from 30 to 50 amp as we also installed a 13,500 AC in the rear bedroom area, where there was a power vent in place. The option was to run a separate 120 line to power the new AC and leave the 30 amp as is. It wasn't a big deal to change to 50 amp, and we can run both ACs at the same time. Of course, we can only run one AC when using the 4000 Onen generator. It has worked quite well. Comparing the cost of trading with the cost of upgrading amps, it proved better to upgrade what we have. Nice having the increased power for other reasons too.

[Chance]

Originally Posted by DLM1965

We recently changed our 2017 Thor Quantum PD31 from 30 to 50 amp as we also installed a 13,500 AC in the rear bedroom area, where there was a power vent in place. The option was to run a separate 120 line to power the new AC and leave the 30 amp as is. It wasn't a big deal to change to 50 amp, and we can run both ACs at the same time. Of course, we can only run one AC when using the 4000 Onen generator. It has worked quite well. Comparing the cost of trading with the cost of upgrading amps, it proved better to upgrade what we have. Nice having the increased power for other reasons too.

If you haven’t already, reading the following thread may be of interest to you if you ever want to power both air conditioners from 4,000-Watt Onan. I don’t know your specifics, but with other major electrical items off, the 4,000 Onan should be able to power two modern and efficient air conditioners provided start-up current is limited. I also don’t know how your Onan is wired to upgraded 50-Amp panel which could make a difference. Just a suggestion.


https://www.thorforums.com/forums/f1...mps-17445.html

[gibbyid]

I would not worry about it. I have a 2016 28Z with only 50 hours or so on the gen and has been hard to start since I got it new. May have a longer line need more prime, but always starts that's all that counts and does the same shaky thing.