Onan shuts off while driving/hot

[jeremywatco]

Hi there,

Having an annoying issue with my Onan 4000 gas generator that is only an issue while driving the motorhome. While stationary its perfect.

So if the genset is running while driving down the road we have found that if it is really hot out and/or driving up a grade while it is hot out the genset will shutoff and refuse to run until conditions change.

The genset is located right behind the engine on our 2014 Fleetwood Storm and by thinking is that excessive engine heat is making its way to the genset and causing it to overheat.

I've made sure oil levels are good and that the fuel level is good.

Yesterday I was driving home from the Sierra's and it was about 109 degree's outside. Wasn't the best drive home when the coach A/C couldnt be ran as the generator wasnt cooperating.

Any thoughts? Anyone else having this issue? If it is a heat issue I am wondering if there is some way to modify the genset compartment to allow better outside ventilation.

[wa8yxm]

Yes. if it shuts down (READ THE FINE MANUAL FOR SPECIFICS) you can press the stop stich. I forget how long but I think it's a tap.. And the active light will flash.. ONE of the fault codes is exhaust over temp

You read the codes (The repeat over and over)
if one code you will get like 3 blinks. 2 blinks 4 blinks . . 3 2 4

if two (Or more) 3 2 4... 2 4 2.. 3 2 4.. 2 4 2.. And so on.

Then you RTFM and.. Well sometimes the code helps. (Sometimes not so much)

[04fxsts]

Last year coming home through Montana around 106 deg. we were just running the engine air and it kept us OK. We pulled into a Walmart to spend the night and the generator would start but shut off. The generator was so hot you could not keep your hand on it so figuring vapor lock. Found a nearby campground with electric and in the morning everything had cooled down and all was fine.
I have wondered if having the generator running would have kept it cooler and running. If I get in that situation again I plan to have the generator running. Maybe the air circulating will keep things cooler? Jim.

[shannonjerry]

We have had this problem twice while traveling. Once was traveling from IL to North Carolina through a ton of mountains and struggled to figure out why as after that all seemed fine. Today we got stuck in Chicago area with rush hour traffic of abrupt stop and goes and I figured out not a mechanical problem per say but a fuel splashing around problem messing up fuel sensors. Hence going through mountains the fuel is moving to one side of tank or other making sensor think low on gas. Same when have to come to a faster stop than normal! Once back to a normal pace and flat surface all works great! Really can't fix it. It is working to detect what it knows of a fuel tank on level ground.

[tippytoe]

I just found a link I had saved - here it is:

http://www.irv2.com/forums/f121/ace-generator-stops-running-code-36-a-125555-61.html

[tippytoe]

About a year ago maybe, there were problems with Fleetwood class C's (and Jaycos also) that have one roof A/C, with the 4000 kw generator installed on left side right behind the front wheel. The factory fixes I believe then was to do some or all of these things: too provide a fresh air intake through the removable cover, move or add fuel pump to near gas tank, move or insulate exhaust pipe so it's not in air intake flow, add sheet metal shield under generator to keep vehicle engine heat away.

There were a lot of discussions of this on this and other forums, but I couldn't seem to instantly find them at the moment.

By the way, our class A with two A/C's and the 5500 generator (behind the left front wheel) came with the added sheet metal shields.

[timmac]

I fix my 5.5 Onan from over heating, maybe I will post pics and explain what I had done to stop it from over heating.

[dougrainer]

Years ago Onan Diesel Gensets had the same problem in Transit. They were mounted up front on Diesel Pushers and when in transit the design of the fresh air intake could NOT pull enough adequate air to keep the Genset from overheating. Onan's solution was simple. You installed the Onan lower air dam that stuck DOWN from the bottom of the genset in front and that allowed the Genset blower wheel to then pull up enough air. The Dam just stuck down about 3 inches. Maybe this is a similar problem and solution. I would be contacting your local Cummins/Onan service center. Doug

[jeremywatco]

Thanks for all the responses. Yes this is an Onan 4000 without oil pressure, its a splash kind.

I have only noticed this behavior when its hot outside while in motion.

I'll see how hard it is to move the fuel pump.

[eHoefler]

Low oil level switch shutting it down while in motion, OP stated while climbing a grade it shut down.

[maddoget]

I changed the fuel line and fuel pump and my problem was solved.

[enblethen]

If this only happens while in motion, I would think an air dam or scoop would get more air flow into the genset.

[MEXICOWANDERER]

Augmentation of cool air intake has saved many a headache. But any additional intake air has to be directed at the generator cooling air intake port.

Can this be done from the access port door? Can a fan be permanently mounted INSIDE the access port door? Or is the door made so flimsy it cannot support 2 lbs of weight which would be aggravated by inertia (bumps)? Sister plating with sheet fiberglass would be feasible.

This critter in the link draws A LOT of air. A gale. Noise obviously is very moot point. Ball bearings and no brushes make my large fans last more than ten years. None have died yet.

http://www.skycraftsurplus.com/6-34metalaxialfan-120vac.aspx

[bounder39zman]

a couple of comments on the problem with generator shutdowns in higher ambient temps; 1st...NEVER run a 4KY(microlite/Microquiet) or newer 5.5 and 7000 Onan gens
with service door removed (except for a quick adjustment maybe).
They will not run cooler, just the opposite. And the mufflers will get hot enough to melt the fiberglass covers. They come with a warning label on the base tray stating this. Hot weather seems to bring out the worst in these air cooled units. Vapor locking can occur if temp in gen compartment is high enough. we have acheived some success by moving fuel pump to cooler location, outside the gen compartment. Only do this on commercial applications, e.g., food trucks, grooming vans, etc.
Most often a fuel pump problem, as they can just stop pumping if they get hot enough. The other problem that we commonly see is the control board stops supplying voltage to fuel pump when it gets hot....usually will restart after a cool-down period. The intermittant nature of problem often makes diagnosis difficult

[ScottG]

DonSmith wrote:
Maybe the additional heat caused the oil pressure to spike?

More heat would actually cause lower oil pressure.

Cheers,
Scott